Trunk
Ventral and Dorsal Body Wall
It has become common practise and is also logic, to study the walls (Paries) of the trunk (Truncus) separately from the content of the cavity, the internal organs, since both parts follow different structural principles.
If one takes the view that the body wall is a structure composed of bones and muscles which surround the internal organs, then it consists of chest (Thorax), Abdomen, and Pelvis. According to this definition, the shoulder girdle (→ p. 135) is not part of the Thorax, since it is only resting on the thoracic walls. whereas the pelvic girdle (→ p. 264) is an integral and definite part of the trunk, as it holds and protects the organs of the lower abdomen.
Skeleton
The trunk (and the neck) is supported by the vertebral column (Columna vertebralis). The vertebral column is composed of single vertebrae and continues throughout the entire length of the trunk. Its most caudal section, the coccyx (Os coccygis), consists of a variable number (4–7) of rudimentary vertebrae. The tip of the tail piece of the coccyx points towards the posterior wall of the Rectum. In the pelvic region, five large single vertebrae are fused by synostosis, resulting in a very rigid vertebral column segment. In contrast, the five lumbar vertebrae (Vertebrae lumbales) enable flexion, extension, and lateral rotation of the vertebral column. The twelve thoracic vertebrae (Vertebrae thoracicae), which articulate with the twelve rib pairs, are notably less mobile.
The superior ten rib pairs (Costae verae et spuriae) are connected to the Sternum, the two inferior pairs (Costae fluctuantes) do not extend to the Sternum. Ribs, thoracic vertebrae, and sternum form the bony thorax or rib cage (Thorax). The ribs are easily palpable on both sides of the Sternum. Starting from the top of the rib cage, the first rib (Costa prima) is not palpable because it is hidden under the clavicle (Clavicula). The second rib (Costa secunda), however, is palpable. Counting the ribs, alongside with the use of auxiliary reference lines, helps identify specific locations on the Thorax. For instance, in an imaginary sagittal line passing through the middle of the clavicle and the fifth intercostal space that is below the fifth rib, the beat of the cardiac apex is palpable. This is where the apex of the heart is “knocking” on the chest wall from the inside.
The cartilaginous costal arch (Arcus costalis), which connects the seventh to tenth rib with the Sternum in an arch-shaped fashion, is also well palpable. It is the landmark for the inferior thoracic aperture, which constitutes a wide opening of the Thorax towards the Abdomen. The thoracic cavity is partitioned by the dome-shaped, steep and upward projecting diaphragm (see below). Abdominal organs, such as stomach, liver, spleen, and others, are located below to the diaphragm and “beneath the cartilage” (Regiones hypochondriacae). The pulsation of the Aorta abdominalis is palpable in the Regio epigastrica between the cartilaginous rib arches and immediately inferior to the xiphoid process (Proc. xiphoideus sterni).
Muscles
The muscles of the abdominal wall are voluntary, like those of the extremities. Muscles are classified into two major groups: muscles acting exclusively on the abdominal wall and muscles of the extremities (arising from the abdominal wall and acting on the shoulder girdle and
the extremities). According to their location and function, the muscles of the wall of the trunk form four major groups: the autochthonous muscles of the back, muscles of the lateral and ventral wall of the trunk, muscles of the diaphragm, and muscles of the pelvic floor. The autochthonous muscles of the back, which consists of numerous single muscles, are located to both sides of the vertebral column. Arranged in two powerful muscle strands, these muscles are oriented in a predominantly craniocaudal direction from the occiput to the pelvic girdle via the neck, thorax and loins. With the back extended, these muscles are particularly visible in the lumbar region. Overall, these muscles are effective in facilitating an erected spine posture, hence they are called M. erector spinae. The adjective “autochthonous” means “rooted or native” – during ontogenesis, all voluntary muscles of the body emerge bilaterally to the vertebral column, precisely the region of the autochthonous muscles of the back in adults. The muscular progenitor (precursor) cells (myogenic progenitor cells) of all other muscles migrate from this region across the ventral side of the trunk towards the extremities. Thus, one should name these “allochthonous” muscles, since they arise from cells “coming from outside”.
The muscles of the lateral and ventral wall of the trunk exist as multilayered intercostal muscles (Mm. intercostales) of the thorax. They assist in respiration. The flanks of the Abdomen (Regiones laterales) contain flat, likewise multilayered muscles, which are also known as lateral abdominal muscles (Mm. obliqui and M. transversus). The anterior abdominal wall is formed by tough tendons (aponeuroses) of these lateral muscles. The straight abdominal muscle (M. rectus abdominis) extending longitudinally from the symphysis to the chest is ensheathed in these aponeuroses (“six-pack belly”). Together, these muscles rotate and flex the trunk. Beyond this, these muscles also control the tension of the abdominal wall, assist in expiration as well as in vocalization for speech and singing, and increase abdominal pressure.
The diaphragm (Diaphragma), the most important muscle of respiration, is voluntary, even though one is not aware of its actions. The diaphragm is located in the interior of the trunk, arises from the margins of the inferior thoracic aperture (see above) and forms a large thin-walled dome with the apex pointing towards the thoracic cavity. During contraction, the dome flattens and this leads to an increased volume of the thoracic cavity facilitating inhalation.
The muscles of the pelvic foor (Diaphragma pelvis and urogenitale) are also voluntary (pelvic floor exercise). They bear the weight of the visceral organs (caudally the bony pelvis is open). These muscles originate from the inner lower margins of the bony pelvis to form a funnel that tapers down towards the caudal end (→ p. 196 and 214).
Breast (Mamma)
The breasts (Mammae) are located on the female thorax – more precisely: they ride on top of the M. pectoralis major, a muscle of the shoulder girdle. Their major component is subcutaneous adipose tissue and only a small part consists of glandular tissue (Glandulae mammariae). Each mammary gland comprises 10 to 20 single glands (Lobi) and each gland sends its own efferent duct to the mammilla (Papilla mammaria). Only during breastfeeding (lactation period) – or in the presence of a malignant breast tumour – the glandular tissue proliferates, which should only serve the production of milk. Men also have tiny rudimentary mammary glands. They can also accumulate abundant adipose tissue in the breast region on top of the M. pectoralis (gynecomastia).
→Dissection Link
After preparation of the skin, the Mm. trapezius and latissimus dorsi as well as the Fascia thoracolumbalis are exposed. The M. trapezius is separated at its origin; the M. latissimus dorsi is separated in an arch-shaped manner near its origin. After dissection of blood and nerve vessels of the muscles, the Mm. levator scapulae and rhomboidei are exposed and the Trigonum lumbale fibrosum is defined. Following the removal of the origin of the M. latissimus dorsi, the structures passing through the axillary gaps are exposed. The Mm. serrati posteriores are exposed after removal of the Mm. rhomboidei at their origin. Subsequently, dissection of the M. erector spinae and the deep (internal) neck region occurs. Upon completion, the Mammae on the ventral side of the body are dissected and removed, the epifascial pathways are traced to thigh and upper arm, and the dissection of the axilla and MOHRENHEIM’s fossa is completed. After removal of the M. pectoralis major, the Claviculae are exarticulated, the abdominal muscles are opened, the inguinal canal and the structure of the spermatic cord are exposed, the rectus sheath and the scrotum are opened and the testicular fasciae are displayed. In women, the inguinal canal is located along with the Lig. teres uteri.
Surface anatomy
Back
Fig. 2.1 Back, Dorsum, surface relief of the back.
The contours of the back provide useful landmarks to determine different regions of the vertebral column, muscles, the approximate position of the end of the spinal cord, and the position of organs (e.g. kidney). Bony landmarks are the Proc. spinosus of the 7th cervical vertebra (Vertebra prominens), the acromion, the Spina scapulae, the Angulus inferior scapulae, and the Proc. spinosus of the 5th lumbar vertebra.
Fig. 2.2 Regions and orientation lines of the back.
The back and neck region have the following distinct topographic regions: Regio cervicalis posterior (Regio nuchalis), Regiones vertebralis, scapularis, infrascapularis, deltoidea, lumbalis, sacralis, and glutealis. Useful orientation lines of the back include the Linea mediana posterior, paravertebralis, scapularis, and axillaris posterior.
Thoracic and abdominal wall
Fig. 2.3 Surface relief of the chest and the abdominal wall of a young woman.
Landmarks assist in the orientation at the ventral side of the trunk, like e.g. the costal arch (Arcus costalis), the umbilicus (Anulus umbilicalis), and the Spina iliaca anterior superior.
Additional landmarks are shown.
Development
Development
Fig. 2.5 Development of the walls of the trunk: organization of the somites at week 4. [21]
All elements of the supportive and muscular systems of the ventral and dorsal trunk originate exclusively from the middle germ layer (Mesoderm). The mesoderm condenses on both sides of the Chorda dorsalis and the neural tube to form somites and unsegmented lateral mesoderm. At week 4, a ventromedial section of each somite differentiates to become a sclerotome. Migrating cells of the sclerotomes on both sides of the neural tube and the notocord (Chorda dorsalis) meet to form primitive vertebrae. Derivatives of the lateral section of each somite are the myotome and the dermatome which contribute cells for the development of the muscles and skin, respectively.
Figs. 2.6a to c Development of the walls of the trunk: differentiation of epimere and hypomere from myotomes. [21]
The striated skeletal muscles of the trunk originate from dermatomyotomes in the lateral section of the somites and starts differentiating at week 4. During week 5, a larger ventral group of mesenchymal cells, the hypomere, separates from a smaller dorsal cell population, the epimere. The hypomere is the origin of the Mm. scaleni, prevertebral neck muscles, infrahyoid muscles, Mm. intercostales, subcostales, transversus thoracis, oblique abdominal muscles, Mm. rectus abdominis, quadratus lumborum, pelvic floor muscles, and sphincter muscles of the anus and urethra. The autochthonous muscles of the back (M. erector spinae) derive from the epimere. In the region of the abdominal wall, the hypomere differentiates into the oblique and rectus abdominal muscles at week 7; the epimere forms part of the autochthonous back muscles. Epimere and hypomere receive separate nerve innervation: these are the Rr. ventrales and Rr. dorsales of the spinal nerves for the hypomere and epimere, respectively.
Fig. 2.7 Development of the wall of the trunk: Nuclei pulposi as remnants of the Chorda dorsalis in the adult vertebral column. [21]
From the beginning of week 4 of development, migrating cells from the scerotome assemble around the neural tube. A fraction of cells encir-cles the Chorda dorsalis and differentiates to become the vertebral body. The Chorda regresses to become the small jelly-like Nucleus pulposus in the centre of the intervertebral discs.
Figs. 2.8a and b Development of the ribs and the sternum. [21]
The sternum develops from two sternal bars which derive from parallel condensations of mesenchymal cells in the ventrolateral body wall (a) and fuse cranio-caudally in the median plane (b). Ossification of the Proc. xiphoideus occurs late at 20–25 years of age. The ribs in the re-gion of the thoracic vertebral column and the Procc. costales of the neck and lumbar vertebrae derive from sclerotome cells that have migrated ventrolaterally. Dorsally they are connected with the vertebrae and ventrally they connect in part with the Sternum (ribs I to VII; true ribs, Costae verae). The ribs VIII. to X fuse ventrally and connect to the sternum in an arch via their own cartilage (false ribs, Costae spuriae). Ribs XI and XII are exclusively connected with the vertebrae and end freely (Costae fluctuantes) in the ventral chest wall.
Fig. 2.9a and b Development of vertebral bodies from two adjacent sclerotomes. [21]
Sclerotomes divide into a cranial and caudal section. A myotome is associated with a sclerotome and receives innervation by a spinal nerve. In between the sclerotomes and the myotomes course the intersegmental blood vessels (week 6, a). The individual vertebrae are formed by the fusion of a caudal with a neighbouring cranial sclerotome section. Each spinal nerve associated with a myotome becomes sandwiched during the fusion of the cranial and caudal sclerotome sections and exits through a Foramen intervertebrale. Intervertebral discs develop between the primordial vertebrae (b). Muscles derived from a single myotome (e.g. M. rotator brevis, → Fig. 2.78) can move two neighbouring vertebrae into opposite directions. The functional unit of all structures participating in the motion of two neighbouring vertebrae is called a motion segment.
Skeleton
Skeleton of the trunk
Fig. 2.10 and Fig. 2.11 Bones and cartilages of the skeletal trunk;
ventral views (→ Fig. 2.10) and dorsal view (→ Fig. 2.11). The bones of the thorax (Ossa thoracis) as well as the bones of the vertebral column (Columna vertebralis) and the pelvic girdle (Cingulum pelvicum) are shown.
Although all ribs articulate with the vertebral column, only the first seven ribs are directly connected to the sternum via their cartilage processes (Cartilago costalis). They are named true ribs (Costae verae). The remaining five pairs of ribs are false ribs (Costae spuriae); ribs XI and XII fail to connect with the cartilaginous arch (Costae fluctuantes).
The rhomboid-shaped connection formed by the Proc. spinosus of the fourth lumbar vertebra with the Spinae iliacae posteriores superiores and the superior part of the Crena ani at the backside of a woman is named the MICHAELIS’ rhomboid. In men, the sacral triangle (connection between Spinae iliacae posteriores superiores and the superior part of the Crena ani) is visible.
* clinical term: angle of LUDWIG (LUDOVICUS)
** Costae fluctuantes (Costae XI–XII)
Ribs
Fig. 2.12 Ribs, Costae; ribs I to III: cranial view; rib VIII: caudal view.
Ribs III to X are typically shaped. The head of the rib (Caput costae) is wedge-shaped and possesses two articular surfaces (Facies articulares capitis costae). The Tuberculum costae has one surface (Facies articularis tuberculi costae). The V., A., and N. intercostalis run in close proximity to the Sulcus costae. An invagination at the ventral end of the body of the rib (Corpus costae) facilitates contact with the rib cartilage.
Ribs I, II, XI, and XII deviate from the typical rib structure. Rib I is stumpy, broad, and shows the strongest curving; the head has only one articular surface. Rib II displays only an outline of a Sulcus costae and a Tuberositas musculi serrati anterioris marks the origin of the M. serratus anterior. The heads of ribs XI and XII contain only one articular surface. These two ribs fail to contact with the costal arch, show pointed ventral ends, and have no Tuberculum costae.
Vertebral column
Fig. 2.13 and Fig. 2.14 Vertebral column, Columna vertebralis; ventral (→ Fig. 2.13) and dorsal (→ Fig. 2.14) views.
The vertebral column accounts for 40% of the height of a human, a quarter thereof being due to the intervertebral discs. The vertebral column is composed of 24 presacral vertebrae (seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae) as well as two synostotic parts, the sacral (Os sacrum) and the coccygeal bone (Os coccygis). The thoracic vertebrae connect with the twelve rib pairs, the sacrum articulates with the Ossa coxae. In the upright position, the physical force increases from cranial to caudal along the vertebral column.
Fig. 2.15 Vertebral column, Columna vertebralis; view from the left side. When viewed in the sagittal plane the vertebral column has a characteristic curvature:
• cervical lordosis (ventral convex curvature)
• thoracic kyphosis (dorsal convex curvature)
Lordosis and kyphosis are the medical terms for ventrally and dorsally directed convex curvatures of the vertebral column, respectively. In the first few months after birth, all sections of the vertebral column show a dorsal convex bend. The cervical lordosis develops with the ability to sit upright and the lumbar lordosis forms when learning to walk.
The vertebral curvatures form only after the pelvis has tilted forward as a result of the bipedal walk learned at the age of 1–2 years. Prior to this ability to walk upright, all sections of the vertebral column show a dorsal convex curvature.
Atlas and axis
Fig. 2.16 Base of occipital bone, Os occipitale, region of the Foramen magnum and the occipital condyles for the upper head joint; caudal view.
The occipital condyles are located bilaterally to the Foramen magnum..
Fig. 2.17 1st Cervical vertebra, Atlas; cranial view.
The atlas does not possess a vertebral body. During development, the latter fused with the axis to form the Dens. The anterior vertebral arch (Arcus anterior atlantis) is positioned anterior to and articulates with the dens. At the posterior vertebral arch (Arcus posterior atlantis), the Proc. spinosus is replaced by a small Tuberculum posterius. The upper articular facets of the atlas are frequently separated into two sections. Compared to other vertebrae, the atlas has a slightly longer transverse process.
* variant: Canalis arteriae vertebralis
Fig. 2.18 1st Cervical vertebra, Atlas; caudal view.
The Fovea dentis articulates with the Dens axis and is located on the inside of the Arcus anterior atlantis. The Facies articulares inferiores are shallow, concave, and tilted in a 30o angle to the transverse plane. The Foramen transversarium is typical for cervical vertebrae and facilitates the passage of the A. vertebralis.
Fig. 2.19 1st and 2nd cervical vertebrae, Atlas and Axis; median section; view from the left side.
The median section permits the inspection of the vertebral canal. Atlas and axis articulate via the Fovea dentis and the Facies articularis anterior in the Articulatio atlanto-axialis mediana. The Arcus posterior atlantis is considerably smaller in relation to the Arcus vertebrae of the axis.
Cervical vertebrae
Fig. 2.20 and Fig. 2.21 2nd cervical vertebra, Axis; ventral (→ Fig. 2.20) and dorsocranial (→ Fig. 2.21) views.
A distinct feature that sets the axis apart from the other cervical vertebrae is the dens. The front and rear side of the dens are covered with articular facets (Facies articulares anterior et posterior). The articular facets of the Procc. articulares superiores are sloped to the outside and the Procc. articulares inferiores are positioned in an oblique angle to the frontal plane. Starting with the 3rd cervical vertebra, the articular facets of the Procc. articulares superiores also assume an oblique position in relation to the frontal plane. The transverse process of the axis (Proc. transversus) is short and the spinous process (Proc. spinosus) is frequently split in two.
Fig. 2.22 5th cervical vertebrae, Vertebra cervicalis V; cranial view.
The 5th cervical vertebra exemplifies the typical structure of the 3rd to 6th cervical vertebrae. With the exception of the 7th cervical vertebra, the Proc. spinosus has two pointed ends. The Proc. transversus is short, has a Foramen transversarium and ends laterally in a Tuberculum anterius and in a Tuberculum posterius, with the Sulcus nervi spinalis located between them. The Foramen vertebrale is large and triangular. The vertebral body is longer in the transverse axis than in the sagittal axis and similarly wide at the front and back.
Fig. 2.23 7th cervical vertebra, Vertebra cervicalis VII; cranial view.
The 7th cervical vertebra has a long transverse process with a Tuberculum posterius only and a long and undivided spinous process.
Fig. 2.24 2nd to 7th cervical vertebrae, Vertebrae cervicales II–VII; ventral view.
The 3rd to 6th cervical vertebrae have a typical structure, whereas the 1st, 2nd, and 7th cervical vertebrae deviate from this structure. The upper surfaces display a lip projecting upward at either side (Unci corporis). The Unci corporis are also named Procc. uncinati and articulate in the Articulatio (Hemiarthrosis) uncovertebralis with the lateral and caudal parts of the Corpus vertebrae of the above vertebra.
* so-called uncovertebral gaps
Fig. 2.25 1st to 7th cervical vertebrae, Vertebrae cervicales I–VII; lateral dorsal view.
The long and undivided spinous process of the 7th cervical vertebra can be easily palpated in the neck and is therefore also named Vertebra prominens. However, this cervical vertebra can be confused with the 1st thoracic vertebra which has an even more pronounced spinous process. The articular facets (Facies articularis superior or inferior) of a vertebral process (Proc. articularis superior or inferior) articulate with the corresponding partner in the Articulatio zygapophysialis.
Thoracic vertebrae
Fig. 2.26 Vertebra: example detailing the structure of the 5th thoracic vertebra; cranial view.
The vertebral arch (Arcus vertebrae) is divided in the Pediculus arcus vertebrae and the Lamina arcus vertebrae. Coming off the arch are bi-laterally the Procc. transversi and dorsally the Proc. spinosus. Articular facets are located cranially and caudally and participate in the formation of the vertebral joints (zygapophyseal joints). The lateral cranial and caudal aspects of the vertebral body each possess a fovea for the articulation of the costal head (Fovae costales superior and inferior). In the Articulatio costotransversaria at the Proc. transversus, the Fovea costalis articulates with the facet of the Tuberculum costae of the corresponding rib.
* also: annular rim
Fig. 2.27 6th thoracic vertebra, Vertebra thoracica VI; view from the left side.
View of the articular facets for the costal heads (Foveae costales superior and inferior), the articular facets of the zygapophyseal joints positioned almost in the frontal plane (Procc. articulares superior and inferior), the facets (Foveae costales) for the articulation with the Tuberculum costae of the ribs, the Incisura vertebralis inferior and the Proc. spinosus pointing sharply downwards.
Fig. 2.28 10th thoracic vertebra, Vertebra thoracica X; ventral view onto the vertebral body with superior and inferior intervertebral surface.
The articular facets of the Procc. articulares extend beyond the vertebral body cranially and caudally.
Fig. 2.29 12th thoracic vertebra, Vertebra thoracica XII; view from the left side.
The 12th thoracic vertebra has a singular bilateral Fovea costalis and displays structural similarities to a lumbar vertebra: the inferior articular processes point laterally. In addition, this vertebra possesses Procc. mamillares and accessorii.
*area of the vertebral arch between the upper and lower articular process (so-called isthmus = interarticular portion)
Thoracic and lumbar vertebrae
Fig. 2.30 10th to 12th thoracic vertebrae, Vertebrae thoracicae X–XII, and 1st to 2nd lumbar vertebrae, Vertebrae lumbales I–II; left dorsal view.
The lumbar vertebrae are larger and structurally more compact to withstand the increased compression forces imposed by the body weight. The Procc. spinosi are short, podgy, and point almost straight backward. The arches of the lumbar vertebrae are the origin of the Procc. costales (derived from the primordial ribs fused with the vertebrae), the variably large Procc. accessorii, the Procc. articulares superiores (supporting the upper articular facets, Facies articulares), the Procc. mamillares (remnants of the Proc. transversus), and the Procc. articulares inferiores with the lower articular facets (Facies articulares).
Lumbar vertebrae
Fig. 2.31 3rd lumbar vertebra, Vertebra lumbalis III, of an elderly person; median section; view from the left side.
The articular facets of the Procc. articulares superiores are facing each other (that is the reason why they are not clearly visible from the side) and articulate with the inferior articular processes of the adjacent higher vertebra.
* ossification of ligamentous attachments
Fig. 2.32 and Fig. 2.33 4th lumbar vertebra, Vertebra lumbalis IV; cranial (→ Fig. 2.32) and ventral (→ Fig. 2.33) views.
The Pediculus arcus vertebrae is proportionally very large in comparison to the size of the lumbar vertebra. At the lateral aspect of the arch, the different processus are visible (Procc. costales, accessorii, mamillares, and articulares superiores and inferiores) and posterior the strong Proc. spinosus. When viewed from the ventral side, the lumbar vertebra has a massive body (Corpus vertebrae) with pronounced upper and lower intervertebral surfaces (Facies intervertebrales superior and inferior). The articular facets of the zygapophyseal joint extend beyond the cranial and caudal part of the vertebral body.
* also: superior vertebral end plate
** also: inferior vertebral end plate
Sacrum
Figs. 2.34 to 2.36 Sacrum, Os sacrum; dorsal (→ Fig. 2.34), ventral (→ Fig. 2.35), and cranial (→ Fig. 2.36) views.
The dorsal surface (Facies dorsalis) displays five longitudinal crests of different intensity formed by the fusion of the corresponding vertebral processes. The Crista sacralis mediana results from the fusion of the Procc. spinosi, the Crista sacralis medialis corresponds to the fusion of the Procc. articulares, and the Crista sacralis lateralis represents the fusion of the rudimentary lateral processes. The Crista sacralis mediana terminates above the Hiatus sacralis which represents the caudal opening of the vertebral canal. In children, this opening is utilized for sacral anaesthesia.
The pelvic surface (Facies pelvina) displays the fused margins of the sacral vertebrae (Linae transversae) and the paired Foramina sacralia anteriora, where the branches of the spinal nerves exit. The Pars lateralis of the Os sacrum is located lateral to the Foramina sacralia anteriora. Visible from the top, the Basis ossis sacri is the contact surface for the intervertebral disc with the 5th lumbar vertebra. This intervertebral disc extends farthest into the pelvis and, together with the anterior rim of the Basis ossis sacri, is named the Promontorium. Lateral to the Basis ossi sacri, the Alae ossis sacri extend as cranial portion of the Partes laterales. Located posterior to the base is the triangular sacral canal and laterally thereof are the Procc. articulares superiores for articulation with the 5th lumbar vertebra.
Sacrum and coccyx
Fig. 2.37 Sacrum, Os sacrum; view from the right side.
The lateral view shows the Facies articularis, which is part of the joint with the Os coxae (Articulatio sacroiliaca). The Tuberositas ossis sacri is located at its dorsal aspect and serves as an insertion region for ligaments.
Fig. 2.38 Sacrum, Os sacrum; median section; view from the right side.
* In adults, remnants of the intervertebral discs can remain. In addition, incomplete fusions of sacral vertebrae are frequently found.
Fig. 2.39 Sacrum, Os sacrum; differences in sex.
Men have a slightly longer and narrower sacrum than women. The shape of the sacrum female contributes to the wider shape of the female pelvis which is advantageous during parturition.
Fig. 2.40 Sacrum, Os sacrum; differences in sex.
The male sacrum is bent more than the female sacrum.
Fig. 2.41 Coccyx, Os coccygis; ventral cranial view.
The coccyx is formed from three to four vertebrae but can also be made up of five rudimentary vertebrae as is shown here. The coccyx is connected to the Os sacrum via the Cornua coccygea and the rudimentary vertebral body.
Sternum
Fig. 2.43 and Fig. 2.44 Sternum; ventral (→ Fig. 2.43) and lateral (→ Fig. 2.44) views.
The Sternum is composed of the Manubrium and the Corpus sterni, and of the Proc. xiphoideus. Its upper end forms the Incisura jugularis which is the ventral upper margin of the upper thoracic aperture and articulates with the clavicles through the Incisurae claviculares and with the ribs I to VII via the Incisurae costales. Manubrium and Corpus sterni are connected by the Symphysis [Synchondrosis] manubriosternalis, whereas the Corpus sterni and Proc. xiphoideus articulate through the Symphysis xiphosternalis. The Proc. xiphoideus can be divided.
* angle of LUDWIG (LUDOVICUS)
Fig. 2.45 Sternum and origin of cartilaginous parts of the ribs, Cartilagines costales; frontal section.
Only part of the costosternal insertions are true joints. Synchondroses are common (ribs I, VI and VII).
Fig. 2.46 Sternoclavicular joints, Articulationes sternoclaviculares; ventral view; right frontal section through the joint.
The sternoclavicular joint is a functional ball and socket joint with three degrees of freedom in movement. It contains a Discus articularis of fibrous cartilage, dividing the joint into two chambers (dithalamic joint). The shape of this joint is a reflection of the demands of multiaxial mobility and very diverse mechanical stresses during different joint positions. Because the discus is able to absorb high shear forces, the articular facets can be kept small. The Ligg. sternoclavicularia anterius and posterius, interclaviculare and costoclaviculare strengthen the joint capsule.
Ligaments of the vertebral column
Fig. 2.47 Ligaments of the vertebral column using the example of the lower thoracic vertebral column; ventral view.
The anterior longitudinal ligament (Lig. longitudinale anterius) ranges from the Tuberculum anterius of the Atlas to the Os sacrum. It is fixed to the anterior surface of the vertebral bodies and to the intervertebral discs (Disci intervertebrales). This ligament increases the stability of the vertebral column during extension.
Fig. 2.48 Ligaments of the vertebral column using the example of the lower thoracic and upper lumbar vertebral column; dorsal view.
The posterior longitudinal ligament (Lig. longitudinale posterius) is a continuation of the Membrana tectoria and extends to the Canalis sa-cralis. It is fixed to the intervertebral discs and the rims of the intervertebral surfaces and secures the intervertebral discs (Disci intervertebrales). This ligament increases the stability of the vertebral column during flexion.
Fig. 2.49 Costovertebral joints, Articulationes costovertebrales; transverse section through the lower part of the costovertebral joint; cranial view.
The costal heads articulate with the thoracic vertebra/vertebrae in the Articulatio capitis costae. With the exception of the ribs I, XI and XII, this is a two-chambered joint (dithalamic joint). Each costal head articulates with the upper and lower rim of two adjacent vertebrae and, through a ligament (Lig. capitis costae intraarticulare; not visible), the intervertebral disc is fixed to the Crista capitis costae. In addition, the rib articulates with the Proc. transversus of the cranial vertebra in the Articulatio costotransversaria (exception are ribs XI and XII). This involves the Facies articularis tuberculi costae of the rib and the Fovea costalis processus transversi of the vertebral transverse process. The weak joint capsules are strengthened by different ligaments (→ Fig. 2.50).
Fig. 2.50 Connections of the vertebral arches; ventral view.
In between the vertebral arches stretch the segmental Ligg. flava (yellow colour results from the high content of elastic fibres oriented perpendicular to each other). They form the dorsal demarcation of the Foramina intervertebralia. The Ligg. flava are always under tension and support the muscles of the back when erecting the vertebral column from all flexed positions.
Fig. 2.51 Ligaments of the vertebral column and the costovertebral joints, Articulationes costovertebrales; view from the left side; lateral parts of the anterior longitudinal ligament removed.
The joint capsules of the Articulationes capitis costae are strengthened by the Ligg. capitis costae radiata; the joint capsules of the Articulationes costotransversariae are supported by the Ligg. costotransversaria (Lig. costotransversarium laterale and Lig. costotransversarium superius).
Fig. 2.52 Ligaments of the vertebral column and the costovertebral joints, Articulationes costovertebrales; dorsal view.
The dorsal part of the joint capsules of the Articulationes transversariae is strengthened by the Ligg. costotransversaria laterales and superiora. The Ligg. intertransversaria guarantee additional stability.
* The Lig. supraspinale is the median part of the Fascia thora-columbalis.
Motion segment
Fig. 2.53 Lumbar motion element; median section; view from the left side.
The intervertebral disc (Discus intervertebralis) is composed of a central gelatinous nucleus (Nucleus pulposus), a remnant of the Chorda dorsalis, and a ligamentous ring (Anulus fibrosus), which surrounds the Nu-cleus pulposus. The Anulus fibrosus is the non-ossified remnant of the epiphysis of the vertebral body (*). Its main attachment is to the Corpus vertebrae at the bony rim and the hyaline cartilaginous lining (**) of the intervertebral surface and the Lig. longitudinale posterius. Additional, although weaker, fixation is provided by the Lig. longitudinale anterius. A Discus intervertebralis acting as Symphysis intervertebralis connects two neighbouring vertebrae. The Ligg. flava interspinale and supraspinale provide the connection between the vertebral arches. In the thoracolumbar region, the Lig. interspinale projects into the Fascia thoracolumbalis.
* annular rim
** hyaline cartilaginous lining of the intervertebral surface
Cervico-occipital joints
Fig. 2.54 Cervico-occipital joints with deep ligaments; dorsal view.
The Membrana tectoria is the cranial extension of the Lig. longitudinale posterius and covers the ligaments and the joint capsule of the Articulatio atlanto-axialis mediana (not visible). Lateral between Os occipitale and Atlas the joint capsule of the Articulatio atlantooccipitalis and between Atlas and Axis the joint capsule of the Articulatio atlantoaxialis lateralis are visible.
Fig. 2.55 Cervico-occipital transitional region with intermediate atlanto-axial joint and corresponding ligaments; sagittal section through the median plane; view from the left side.
A section through the articular connection between Dens axis and anterior arch of the Atlas is shown. This is part of the so-called lower head joint composed of the Articulationes atlantoaxiales laterales and the Articulatio atlantoaxialis mediana as opposed to the upper head joint which consists of the Articulationes atlantooccipitales. Above and below the Atlas, the joint capsule receives support through the Mem- brana atlantooccipitalis anterior and the upper part of the Lig. longitudinale superius, respectively. On the posterior side of the dens, the joint capsule is strengthened by the Fasciculi longitudinales and the Lig. transversum atlantis (jointly named Lig. cruciforme atlantis) as well as the Membrana tectoria which covers the Lig. cruciforme atlantis. The Membrana tectoria is covered by the Dura mater spinalis. The Mem-brana atlantooccipitalis posterior extends between the Os occipitale and Atlas at the dorsal aspect of the vertebral canal.
Fig. 2.56 Cervico-ocipital joints with deep ligaments; dorsal view; after removal of the Membrana tectoria.
Centrally located is the Lig. cruciforme atlantis composed of the Lig. transversum atlantis and the two Fasciculi longitudinales. Behind this ligament the Ligg. alaria (winged ligaments) are located which origi-nate from the tip and the lateral surface of the Dens axis (→ Fig. 2.57); they project upwards in an oblique angle. On the left side, the joint capsule of the Articulatio atlantooccipitalis and the Articulatio atlantoaxialis are shown. On the right side, the joint capsules have been removed and the joint cavity is visible.
Fig. 2.57 Cervico-occipital joints with deep ligaments; dorsal view; after removal of the Membrana tectoria and Lig. cruciatum atlantis.
One can see the Ligg. alaria (→ Fig. 2.56) which frequently project to the Massae laterales of the Atlas and the thin Lig. apicis dentis.
Fig. 2.58 Cervico-occipital joints with ligaments and upper cervical vertebral column; ventral view.
The Lig. longitudinale anterius is located in the midline. The Membrana atlantooccipitalis anterior extends from the occipital bone to the Atlas. The joint capsule of the Articulatio atlantooccipitalis is shown on the ride side and removed on the contralateral side.
Fig. 2.59 Cervico-occipital joints; dorsal view.
Dorsal view onto the Membrana atlantooccipitalis posterior and the Lig. atlantooccipitale laterale between the Os occipitale and the Arcus posterior atlantis. The joint capsule of the Articulatio atlantoaxialis lateralis between Atlas and Axis is shown on the ride side and removed on the contralateral side.
Intervertebral discs
Figs. 2.60a and b Intervertebral discs, Disci intervertebrales.
a. Cervical intervertebral discs, Disci intervertebrales cervicales; frontal section; ventral view.
In the lateral areas of the cervical intervertebral discs so-called uncovertebral gaps (**) start forming already during the first decade of life. Between 5 to 10 years of age, the gaps become manifest and assume a joint-like character, hence their name uncovertebral joints. While providing increased flexibility of the cervical vertebral column at a younger age, later on these uncovertebral joints may rupture completely and, thus, can impact negatively on neck mobility (→ Clinical Remarks).
b. Lumbar intervertebral disc, Discus intervertebralis lumbalis; median section ( → Fig. 2.53); view from the left.
* hyaline cartilaginous lining of the intervertebral surface as part of the non-ossified portion of the vertebral epiphyses
** so-called uncovertebral gap
Fig. 2.61 Lumbar intervertebral disc, Discus intervertebralis lumbalis; cranial view.
The intervertebral disc (Discus intervertebralis) is composed of a central jelly-like nucleus (Nucleus pulposus), a remnant of the Chorda dorsalis, and a fibrous ring (Anulus fibrosus) surrounding the Nucleus pulposus.
Imaging
Cervical region of the vertebral column, radiography
Fig. 2.62 Cervical vertebrae, Vertebrae cervicales; lateral radiograph of the cervical part of the vertebral column; upright position; the central beam is directed onto the 3rd cervical vertebra; shoulders are pulled downwards.
Thoracic region of the vertebral column, radiography
Fig. 2.63 Thoracic vertebrae, Vertebrae thoracicae; anterior-posterior (AP) radiograph of the thoracic part of the vertebral column; upright position with Thorax in inspiration; central beam is directed onto the 6th thoracic vertebra.
* intervertebral disc space
Lumbar region of the vertebral column, radiography
Fig. 2.64 Lumbar vertebrae, Vertebrae lumbales; lateral radiograph of the lumbar part of the vertebral column; upright position; central beam is directed onto the 2nd lumbar vertebra. The anterior edges of the lower lumbar vertebrae are oblique as an initial sign of degenerative changes and pathological alterations.
* intervertebral disc space
** region of the vertebral arch between the superior and inferior articular processes (isthmus = interarticular portion)
*** The terminal points indicate the position of the XII. rib, which is poorly visible in this copy of the radiograph.
Fig. 2.65 Lumbar vertebrae, Vertebrae lumbales, and sacrum, Os sacrum; AP-radiograph of the lumbar part of the vertebral column and sacrum; upright position; central beam is directed onto the 2nd lumbar vertebra.
* intervertebral disc space
Fig. 2.66 Lumbar vertebrae, Vertebrae lumbales; radiograph with beam in an oblique angle; upright position. [8]
The experienced radiologist can recognize a dog-like figure (“Scotty dog”, dotted lines) in this oblique radiograph image. The central part represents the interarticular portion. The clinical term refers to the superior and inferior articular facets of the zygapophyseal joints (→ Fig. 2.29).
* interarticular portion
Vertebral column, CT
Fig. 2.67 Cervical part of the vertebral column; computed tomographic (CT) cross-section at the level of the intervertebral disc between the 4th and 5th cervical vertebrae.
* endotracheal tube and endoscopic instrument
Fig. 2.68 Cervical part of the vertebral column; computed tomographic (CT) cross-section at the level of the 5th cervical vertebra.
Fig. 2.69 Lumbar part of the vertebral column; computed tomographic (CT) cross-section at the level of the 2nd and 3rd lumbar vertebrae.
Fig. 2.70 Lumbar part of the vertebral column; computed tomographic (CT) cross-section at the level of the pediculi of the 3rd lumbar vertebra.
Vertebral column, MRI
Fig. 2.71 Lumbar part of the vertebral column; magnetic resonance tomographic image (MRI) of the thoracic and lumbar part of the vertebral column and the sacrum.
MRI is a suitable imaging technique to view intervertebral discs, the spinal cord, and the epidural space (Spatium epidurale).
Fig. 2.72 Medial disc prolapse; T2-weighted magnetic resonance tomographic sagittal image (MRI) in the lumbar part of the vertebral column. [8]
Fig. 2.73 Medial disc prolapse; T2-weighted magnetic resonance tomographic axial image (MRI) in the lumbar part of the vertebral column. [8]
Muscles
Superficial layer of muscles of the back
Fig. 2.74 Superficial layer of the trunk-arm and trunk-shoulder girdle muscles; dorsal view.
The Mm. trapezius and latissimus dorsi represent the largest part of the superficial layer of muscles of the back. The M. trapezius secures the scapula and thus the shoulder girdle and can move the scapula and clavicle backwards medially towards the vertebral column. The Partes descendens and ascendens turn the Angulus inferior of the scapula medially. The Pars descendens acts as an adductor and supports the M. serratus anterior in the elevation of the shoulder.
The M. latissimus dorsi is the largest muscle of the human body with respect to the surface area. It lowers the elevated arm, adducts the arm, can move the arm from an adducted position medially and backwards, rotates the arm inward, and assists in expiration. M. latissimus dorsi and M. teres major develop at the same time. The latter pulls the arm medially and backwards, supports adduction, and inward rotation of the arm.
Fig. 2.75 Deep layer of the trunk-arm and trunk-shoulder girdle muscles; dorsal view.
After removal of the M. trapezius, the Mm. levator scapulae, rhomboideus minor and rhomboideus major are visible on the right side. The M. levator scapulae can lift the scapula and simultaneously turns the Angulus inferior of the scapula medially.
M. rhomboideus minor and M. rhomboideus major fix the scapula to the thorax and pull it towards the spine.
After the removal of the three muscles and the M. latissimus dorsi the Mm. serrati posteriores superior and inferior become visible. The M. serratus posterior superior lifts the upper ribs upwards and supports inspiration. The M. serratus posterior inferior broadens the lower tho-racic aperture and stabilizes the lower ribs during the contraction of the Pars costalis of the diaphragm. Thus, this muscle also supports inspiration.
The Fascia thoracolumbalis constitutes a dense aponeurosis. This tough fibrous structure surrounds the autochthonous (intrinsic) erector spinae muscles of the back and forms an osteofibrous tube together with the vertebral column and the dorsal side of the ribs. Its superficial lamina serves as origin for the M. latissimus dorsi and the M. serratus posterior. This lamina is firmly attached to the tendon of the M. erector spinae. It separates the M. splenius cervicis from the M. trapezius and the Mm. rhomboidei in its cranial section and merges with the Fascia nuchae. The deep lamina is shown in → Fig. 2.76.
The areas of the Trigonum lumbale superius (GRYNFELT’s triangle in TA) and the Trigonum lumbale inferius (PETIT’s triangle) are the sites for GRYNFELT’s and PETIT’s lumbar hernias.
Deep layer of muscles of the back
Fig. 2.76 Superficial layer of the deep (autochthonous) muscles of the back; dorsal view.
The autochthonous muscles of the back are collectively named M. erector spinae. It is divided into a medial and a lateral tract. Each tract is composed of different systems (→ Fig. 2.77). The M. erector spinae extends from the sacrum to the occipital bone. The abdominal muscles and the M. erector spinae together act as a functional unit (bow-tendon principle).
Deep layer of muscles of the back, schematic diagram
Fig. 2.77 Deep (autochthonous) muscles of the back; diagram of the different muscle groups.
The autochthonous muscles of the back, collectively named M. erector spinae, can be divided into a longitudinal erector system and an oblique system, as well as in a lateral and medial tract.
The lateral tract divides into an intertransversal system (Mm. intertransversarii), a sacrospinal system (M. iliocostalis, M. longissimus), and a spinotransverse system (M. splenius cervicis, M. splenius capitis):
• The intertransversal system serves as stabilizer, facilitates bending sideways and extension among transverse processes of the vertebrae.
• The sacrospinal system erects the spine, causes extension, and facilitates side-bending and rotational movements of the trunk on the ipsilateral side.
• The spinotransverse system acts as a stabilizer according to the bow-tendon principle and, together with the short neck muscles, supports all movements generated in the joints of the cervical spine and head.
The medial tract divides into a spinal system (Mm. interspinales, M. spinalis) and a transversospinal system (Mm. rotatores breves, Mm. rotatores longi, M. multifidus, M. semispinalis). Functionally, the spinal system is important for extension and torsion; the transversospinal system stabilizes and rotates to the contralateral side.
* spinotransverse
** transversospinal
Deep layer of muscles of the back
Fig. 2.78 Muscles of the back, Mm. dorsi, and muscles of the neck, Mm. suboccipitales; dorsal view.
Upon removal of the Mm. splenius capitis and semispinalis capitis, the short neck muscles (Mm. rectus capitis posterior minor, rectus capitis posterior major, obliquus capitis superior, obliquus capitis inferior) become visible.
Also depicted here are the Mm. levatores costarum which are not part of the autochthonous muscles of the back because they are innervated by Rr. ventrales of the spinal nerves. Contraction of these muscles results in rotation of the contralateral side and side-bending movements on the ipsilateral side. Some authors also discuss a role of this muscle group in inspiration. For the organization of the other shown autochthonous muscles of the back see → Fig. 2.77.
Fig. 2.79 Deep layer of the muscles of the back, Mm. dorsi, in the region of the thoracic and lumbar part of the vertebral column; dorsal view.
On the right side, a cross-section through the caudal region of the M. erector spinae is shown. The Mm. multifidi belong to the medial tract and are located medially, together with the superficial and deep leaf of the Fascia thoracolumbalis. On the left side of the body, the Mm. rotatores thoracis are visible.
Fig. 2.80 Autochthonous muscles of the back; transverse section at the level of the 2nd lumbar vertebra; caudal view.
The autochthonous muscles of the back are located in an osteofibrous tube which is formed by the dorsal parts of the vertebrae at the inside and the Fascia thoracolumbalis on the outside. The autochthonous muscles of the back are divided into a lateral tract (*) and a medial tract (**).
Neck muscles
Fig. 2.81 Short muscles of the neck, Mm. suboccipitales; view from an oblique dorsal angle.
The Mm. rectus capitis posterior major, obliquus capitis superior, and obliquus capitis inferior create a triangle (vertebralis triangle). The M. rectus capitis posterior minor is located medially to the M. rectus capitis posterior major. Functionally, the four muscles direct precise movements of the head joints (Articulationes atlantooccipitalis and atlantoaxialis) and perform minute adjustments of the head in the atlanto-occipital and atlanto-axial joints.
Fig. 2.82 Muscles of the back, Mm. dorsi, and muscles of the neck, Mm. suboccipitales; dorsal view.
To view the short muscles of the neck, the Mm. splenius capitis and semispinalis capitis on the right side were removed. The M. rectus capitis posterior minor has its origin at the Tuberculum posterius of the Atlas and inserts medially at the Linea nuchalis inferior. The M. rectus capitis posterior major originates at the Proc. spinosus of the Axis and inserts laterally to the M. rectus capitis posterior minor at the Linea nuchalis inferior. The M. obliquus capitis superior originates at the Proc. transversus of the Atlas and inserts above and laterally to the M. rectus capitis posterior major. The M. obliquus capitis inferior has its origin at the Proc. spinosus of the Axis and inserts at the Proc. transversus of the Atlas.
Fig. 2.83 Muscles of the neck, Mm. suboccipitales; dorsal view.
The Mm. rectus capitis posterior major, obliquus capitis superior, and obliquus capitis inferior create the margins of the vertebralis triangle (Trigonum arteriae vertebralis). At the base of this triangle the A. vertebralis crosses the Arcus posterior atlantis.
I = Tuberculum posterius of the Atlas
II = Proc. spinosus of the Axis
Fig. 2.84 Muscles of the back, Mm. dorsi, and muscles of the neck, Mm. colli; view from the left side.
Upon dissection of the M. splenius capitis (rest displaced cranially), the lateral view of the neck reveals from anterior to posterior the Mm. scaleni medius and posterior as well as autochthonous muscles of the back with the lateral (Mm. iliocostalis cervicis, longissimus cervicis, splenius cervicis, longissimus capitis) and medial (Mm. semispinalis thoracis, semispinalis capitis) tracts. With the removal of the superficial muscles of the back in the neck region the Lig. nuchae and parts of the M. trapezius become visible at the midline.
Muscles of the thoracic and abdominal wall
Fig. 2.85 Muscles of the thoracic and abdominal wall, Mm. thoracis and Mm. abdominis, superficial layer; ventral view.
The V. cephalica runs between the margins of the M. deltoideus and M. pectoralis major to the Trigonum clavipectorale (MOHRENHEIM’s fossa) where it goes deep to join the V. axillaris. The lower margin of the M. pectoralis major constitutes the anterior axillary fold, the anterior margin of the M. latissimus dorsi creates the posterior axillary fold; the M. serratus anterior forms the floor of the axilla.
The M. pectoralis major functionally participates in the anteversion (= flexion) of the arm in the shoulder joint and is a strong adductor and medial rotator. In addition, this muscle can pull the shoulder forward and downward with the arm in a fixed position and assists in inspiration.
In the abdominal region, the rectus sheath is formed by the aponeuroses of the oblique abdominal muscles. The outmost oblique abdominal muscle, M. obliquus externus abdominis, sends its aponeurosis into the outer layer of the rectus sheath.
In the midline, the aponeuroses join in the Linea alba. The caudal suspensory ligaments for the penis, Ligg. fundiforme and suspensorium penis, are shown. Lateral thereof the Funiculus spermaticus and con-tralaterally the Anulus inguinalis superficialis with Crus mediale, Fibrae intercrurales, and Lig. reflexum are visible.
Fig. 2.86 Muscles of the thoracic and abdominal wall, Mm. thoracis and Mm. abdominis; view from the right side.
The lateral view demonstrates the female breast (Mamma) riding on the M. pectoralis major. The lateral abdominal wall displays the serrated interposition of the muscular origins of the M. obliquus externus abdominis with those of the M. serratus anterior. The M. latissimus dorsi covers these muscular serrations from dorsal.
The M. obliquus externus abdominis extends from lateral posterior cranial to medial anterior caudal. The muscle fibres coming from the lower ribs run almost vertical to the Labium externum of the Crista iliaca. The remaining muscle fibres enter into a sheet-like aponeurosis which participates in the formation of the rectus sheath (Vagina musculi recti abdominis). At the thigh, the Fascia glutea and the Mm. gluteus maximus and tensor fasciae latae radiating into the Tractus iliotibialis are visible.
Fig. 2.87 Muscles of the thoracic wall; Mm. thoracis; ventral view.
The M. pectorals major was removed on both sides, and the M. pectoralis minor was also removed on the left side. On the right side of the body, the course of the neurovascular bundle is visible below the M. pectoralis minor. Although the M. pectoralis minor is considered a muscle of the shoulder it does not insert at the upper extremity but at the Proc. coracoideus. The M. pectoralis minor originates from ribs III to V and participates in depression and rotation of the scapula. The very variable M. sternalis is a not infrequent variant located on top of the M. pectoralis major.
Fig. 2.88 Muscles of the thoracic wall; Mm. thoracis; frontal section through two intercostal spaces.
The following structures are penetrated during pleural puncture: Cutis/Subcutis, Fascia musculi serrati, M. serratus anterior, Fascia thoracica externa, M. intercostalis externus, M. intercostalis internus, Fascia intercostalis interna, Fascia endothoracica, Pleura parietalis. Pleural punctures always are conducted at the upper margin of the rib because the neurovascular structures (V., A., N. intercostalis) run below the rib.
* position of the needle during pleural puncture
Fig. 2.89 Posterior wall of the thoracic cavity, Cavea thoracis; ventral view.
The Mm. intercostales externi project from posterior cranial to anterior caudal. They initiate at the Tubercula costarum and reach forward to the parasternal cartilage (not visible). These muscles act in concert with the Mm. intercartilaginei (not shown) by elevating the ribs during inspiration.
The Mm. intercostales interni project from posterior caudal to anterior cranial. They initiate at the Angulus costae and reach the sternum (not visible). They act during expiration by depressing the ribs. An exception are the muscular parts located between the cartilaginous parts of the ribs (Mm. intercartilaginei) which support inspiration. Not shown are the muscular elements of the Mm. intercostales interni stretching across multiple segments, known as Mm. subcostales, which serve the same function as the Mm. intercostales interni.
Fig. 2.90 Anterior wall of the thoracic cavity, Cavea thoracis; dorsal view.
The view onto the inner side of the anterior thoracic wall displays the sternum and the muscular bundles of the M. transversus thoracis. They originate at the lateral side of the sternum and of the Proc. xiphoideus and insert on the inside of the costal cartilages 2 to 6. The M. transversus thoracis supports expiration.
The posterior side of the Manubrium sterni serves as origin for the M. sternothyroideus and M. sternohyoideus.
Abdominal muscles
Fig. 2.91 Superficial and middle layer of the abdominal muscles, Mm. abdominis; ventral view.
On the right side, the superficial leaf (Lamina anterior) of the rectus sheath (Vagina musculi recti abdominis) has been opened and the M. rectus abdominis becomes visible. This muscle is separated into three to four Intersectiones tendineae which create the so-called six pack contour when exercised properly. The M. rectus abdominis serves to bend the trunk forward and sideways.
The caudal part of the rectus sheath contains the small triangular M. pyramidalis which originates from the Os pubis and projects into the Linea alba. The M. pyramidalis is a rudimentary pouch muscle (from a comparative anatomical standpoint, the kangaroo possesses a strongly developped M. pyramidalis).
On the left side, the M. obliquus externus abdominis has been de-tached and folded medially across the rectus sheath. The larger part of this muscle ends in an aponeurosis which contributes to the superficial leaf (Lamina anterior) of the rectus sheath. Functionally, this muscle participates in the forward and side-bending movements it lateral rotation of the upper torso. It is an element of the oblique and transverse muscular abdominal girdle, and creates a functional unit with the muscles of the opposite side as well as the Mm. obliqui interni and transversi abdominis.
Fig. 2.92 Middle layer of the abdominal muscles, Mm. abdominis; ventral view.
On the right side, the M. obliquus externus abdominis is largely re-moved. Beneath lies the M. obliquus internus abdominis. Its aponeurosis contributes to formation of both the superficial (Lamina anterior) and the deep (Lamina posterior) lamina of the rectus sheath. The M. obliquus internus abdominis projects from lateral caudal to medial cranial and, like the M. obliquus externus abdominis, it participates in the oblique and transverse muscular abdominal girdle and supports forward and side-bending movements and lateral rotation of the upper torso.
Fig. 2.93 Deep layer of the abdominal muscles, Mm. abdominis; ventral view.
On the right abdominal side the M. transversus abdominis is shown. In addition, the anterior lamina (Lamina anterior) of the rectus sheath (Vagina musculi recti abdominis) and the M. rectus abdominis have been removed.
The transition from muscle fibres to the aponeurosis of the M. transversus abdominis forms a semilunar line (Linea semilunaris). This aponeurosis contributes to the major part of the posterior lamina (Lamina posterior) of the rectus sheath. Caudally of the Linea (Zona) arcuata, the aponeurosis of the M. transversus abdominis participates in the formation of the Lamina anterior of the rectus sheath (→ Fig. 2.96). The aponeurosis radiates into the Linea alba. The M. transversus abdominis is mainly exerting a constrictive force which results in increased intra-abdominal pressure and supports forced expiration.
In its upper section (from sternum to Linea [Zona] arcuata), the deep lamina (Lamina posterior) of the rectus sheath is formed by the aponeuroses of both the M. obliquus internus abdominis and the M. transversus abdominis. Below (from Linea [Zona] arcuata to Os pubis), the Lamina posterior only consists of Fascia transversalis and Peritoneum parietale.
Muscle function
Figs. 2.94a to c Directions of motion of the trunk.
a. side-bending movements (lateral flexion) of the trunk
Bending to both sides up to 40° is normal (0°/40°). Vertebra prominens (CVII) and SI serve as reference points when determining the angle in the upright and maximal lateral flexion position. The lateral flexion is supported by the Mm. obliquus externus abdominis, obliquus internus abdominis, quadratus lumborum, iliocostalis, psoas major, longissimus and splenius.
b. Forward (flexion) and backward bending of the trunk (extension) in the vertebral joints
The range of motion is between approximately 100° flexion und 50° extension.
A straight line between the acromion of the scapula and the Crista iliaca of the femur is used to determine these angles. Flexion of the trunk is supported by the Mm. rectus abdominis, obliquus externus abdominis, obliquus internus abdominis, and psoas major. The Mm. iliocostalis, psoas major, longissimus, splenius, spinalis, semispinalis, multifidus, trapezius, and levatores costarum participate in the dorsal flexion of the spine.
c. rotation of the trunk
Bilateral anterior to posterior rotation of the trunk by approximately 40° is possible. A line connecting the acromion of the scapula on both sides serves as a reference axis. Ipsilateral rotation of the trunk is supported by Mm. obliquus internus abdominis, iliocostalis, longissimus, and splenius. Rotation of the trunk to the contralateral side is achieved by the Mm. obliquus externus abdominis, semispinalis, multifidus, rotatores, and levatores costarum.
The vertebral joints in individual sections of the vertebral column restrict the range of movement. As for the entire vertebral column, bending forward (flexion) and backward (extension) of approximately 100°/0°/50°, a side-bending (lateral flexion) of 0°/40°, and a torsion (rotational movement) of 40°/0°/40° are possible; these serve as normal reference values to assess movement restrictions.
Fig. 2.95 Objective assessment of movement restrictions in the lumbar section of the vertebral column (method by SCHOBER) and the thoracic part of the vertebral column (OTT’s sign).
Abdominal muscles, rectus sheath
Figs. 2.96a to c Structure of the rectus sheath, Vagina musculi recti abdominis; cross-section; caudal view.
The Mm. rectus abdominis and pyramidalis are embedded in a tough fibrous tube (Vagina musculi recti abdominis) which is formed by the aponeuroses of the oblique abdominal muscles (Mm. obliquus externus abdominis, obliquus internus abdominis, and transversus abdominis) as well as the Fascia transversalis and the Peritoneum parietale at the inside of the ventral abdominal wall. All aponeuroses radiate into the Linea alba. The upper section of the rectus sheath is different from the lower section. The border between both sections is the Linea (Zona) arcuata.
In the upper section, the anterior lamina (Lamina anterior) of the rectus sheath is formed by the aponeurosis of the M. obliquus externus abdominis and the anterior part of the aponeurosis of the M. obliquus internus abdominis; the posterior lamina (Lamina posterior) is composed of the posterior part of the aponeurosis of the M. obliquus internus abdominis, the aponeurosis of the M. transversus abdominis as well as the Fascia transversalis and the Peritoneum parietale (a, b).
In the lower section, all three aponeuroses locate in front of the M. rectus abdominis (c). Here, the posterior side of the rectus sheath is very thin and composed exclusively by the Fascia transversalis and the Peritoneum parietale (→ Fig. 2.93).
The umbilicus is a potential weak spot in the anterior abdominal wall which is thinner in the region of the umbilical pit and the Papilla umbilicalis as compared to other parts (b).
Abdominal wall, CT
Figs. 2.97a and b Muscles of the abdominal wall, Mm. abdominis; computed tomographic (CT) cross-sections.
The oblique and rectus abdominal muscles can be distinguished in CT scans. The M. erector spinae and the M. quadratus lumborum are also clearly visible.
Inside of the ventral abdominal wall
Fig. 2.98 Posterior aspect of the anterior abdominal wall; dorsal view. On the right side, the fascia and the peritoneum covering the diaphragm and the M. transversus abdominis have been removed.
On the posterior aspect of the ventral abdominal wall different folds (Plicae), pits (Fossae), and ligaments (Ligamenta) are noticeable. The Lig. falciforme hepatis (sickle-shaped liver band) extends between the diaphragm and the liver and inserts in a right angle at the posterior aspect of the ventral abdominal wall. It extends to the umbilicus and represents the developmental remnant of the mesentery of the umbilical vein. The umbilical vein occludes immediately after birth and remains visible as a round ligamentous cord (Lig. teres hepatis) at the free border of the Lig. falciforme hepatis. Below the umbilicus are visible the Plica umbilicalis mediana (median umbilical fold; contains the remnants of the Urachus – the fibrous remnant of the allantois that stretches from the top of the urinary bladder to the umbilicus), lateral thereof the Plicae umbilicales mediales (medial umbilical folds; contain the remnants of the Aa. umbilicales), and farthest lateral the Plicae umbilicales laterales (lateral umbilical folds; contain the Vasa epigastrica inferior). The Fossae supravesicales, inguinales mediales, and inguinales laterales are located between the folds. The Fossa inguinalis lateralis corresponds to the inner inguinal ring located beneath; the Fossa inguinalis medialis locates at the same level as the outer inguinal ring.
Diaphragm and posterior abdominal wall
Fig. 2.99 Diaphragm, Diaphragma, and muscles of the abdominal wall, Mm. abdominis; ventral view.
The diaphragm is composed of a central tendon plate (Centrum tendineum) with attached muscles which have their origin at the sternum (Pars sternalis), the ribs (Pars costalis), and the lumbar region of the vertebral column (Pars lumbalis).
Upon removal of the retroperitoneum, the paravertebral location of the Mm. iliopsoas (composed of a M. psoas major and M. iliacus each), the M. quadratus lumborum, and, as a variant, the M. psoas minor are shown.
Both the M. psoas major, originating from the Fossa iliaca, and the M. iliacus insert at the Trochanter minor of the femur. The M. psoas major represents the strongest flexor of the hip. The M. psoas major can move the upper torso from a lying position into an upright sitting position and participates in the rotation of the trunk. The M. quadratus lumborum originates from the Labium internum of the Crista iliaca and inserts at the XII. rib and at the Procc. costales of the 1st to 4th lumbar vertebrae. This muscle is able to depress the XII. rib and participates in the forward flexion of the trunk.
* FALLOPIAN ligament or POUPART’s ligament
Diaphragm
Fig. 2.100 Diaphragm, Diaphragma; caudal view.
The diaphragm comprises the Centrum tendineum and the Partes sternales, costales, and lumbales. The Trigonum sternocostale (LARREY’s cleft) is located between the Pars sternalis and the Pars costalis, and the Trigonum lumbocostale (BOCHDALEK’s triangle) between the Pars costalis and the Pars lumbalis.
The Pars lumbalis is divided into a Crus dextrum and Crus sinistrum, each of which is separated further into Crura mediale, intermedium, and laterale. The Crus dextrum is attached to the lumbar vertebral bodies of L1 to L3 and the intercalating Disci intervertebrales; the Crus sinistrum is attached to the lumbar vertebrae L1 and L2 and the intercalating Discus intervertebrale. The Crus mediale dextrum forms a loop around the oesophagus (Hiatus oesophageus). The right and left diaphragmatic crura are connected by a tendinous arch (Hiatus aorticus) at the level of the vertebral column. At the Hiatus aorticus the aorta enters the abdominal cavity. The Lig. arcuatum mediale (psoas arcade) demarcates the diaphragm from the M. psoas major, whereas the Lig. arcuatum laterale (quadratus arcade) separates the diaphragm from the M. quadratus lumborum.
Fig. 2.101 Diaphragm, Diaphragma, with diaphragmatic apertures and muscles of the posterior abdominal wall; ventral view.
The diaphragm is a double dome-shaped incomplete separation between the thoracic and abdominal cavity (→ Figs. 2.99 und 2.102).
* clinical term: BOCHDALEK’s triangle
** quadratus arcade
*** psoas arcade
Fig. 2.102 Diaphragm, Diaphragma, and oblique muscles of the abdominal wall, Mm. abdominis; frontal section; ventral view.
The thin and dome-shaped diaphragm is shown. The Partes costales originate laterally from the XI. rib and project into the Centrum tendineum. The diaphragmatic dome positions between the 5th and 6th intercostal spaces during normal breathing. The lateral abdominal wall is composed of the oblique muscles of the abdominal wall (Mm. obliquus externus abdominis, obliquus internus abdominis, and transversus abdominis).
Figs. 2.103a and b Axial (sliding hernia) (a) and para-oesophageal hiatal hernia (b); schematic drawing. [17]
Arteries of the ventral wall of the trunk
Fig. 2.104 Arteries of the ventral wall of the trunk.
The ventral wall of the trunk receives arterial blood through branches of the Aa. subclavia, axillaris, iliaca externa, and femoralis. The muscles of the abdominal wall receive blood through segmentally arranged Aa. lumbales derived from the aorta abdominalis (not shown).
* clinical term: LARREY’s cleft
** clinical term: A. mammaria interna
Vessels and nerves
Arteries of the thoracic wall
Fig. 2.105 Arteries of the thoracic wall.
The intercostal arteries create anastomoses between the A. thoracica interna and the Pars thoracica aortae.
* clinical term: A. mammaria interna
Veins of the ventral wall of the trunk
Fig. 2.106 Veins of the ventral wall of the trunk.
The veins of the ventral wall of the trunk, generate a superficial (shown on the right side of the body) and a deep (left side of the body) system of anastomoses between Vv. cavae superior and inferior.
* clinical term: LARREY’s cleft
** clinical term: V. mammaria interna
Azygos system
Fig. 2.107 Azygos system.
The azygos system drains blood between the V. iliaca interna and the V. cava superior. Hidden from view by the V. cava inferior, the V. lumbalis ascendens on the right side connects the V. azygos with the V. iliaca communis dextra. There are also direct connections of the Vv. lumbales ascendentes with the V. cava inferior. Integrated into this venous system are the Plexus venosus sacralis and the Plexus venosi vertebrales externi and interni as well as the Vv. lumbales.
Arteries and veins of the thoracic wall
Fig. 2.108 Arteries of the thoracic wall. [8]
Aorta and A. thoracica interna communicate through the Aa. intercostales posteriores and the Rr. intercostales anteriores. The A. musculophrenica, a branch of the A. thoracica interna, runs beneath the costal arch. These vessels provide blood to the thoracic and abdominal wall.
* clinical term: A. mammaria interna
Fig. 2.109 Veins of the thoracic wall. [8]
Vv. cavae superior and inferior are connected by the Vv. lumbales, hemiazygos, and azygos. Additional anastomoses exist between the azygos system and the Vv. thoracicae internae via the Vv. intercostales posteriores and anteriores. The veins drain the blood of the thoracic and abdominal wall.
* clinical term: V. mammaria interna
Arteries and veins of the ventral wall of the trunk
Fig. 2.110 Vessels at the posterior aspect of the ventral wall of the trunk; dorsal view.
The epigastric vessels (Vasa epigastrica superior and inferior) run at the posterior side of the M. transversus abdominis and become visible upon removal of the rectus sheath in the upper two thirds of the abdominal cavity and upon removal of the Fascia transversalis in the lower third of the abdominal cavity. The A. thoracica interna on the left side of the body is covered by the M. transversus abdominis. Upon entering the rectus sheath through the Trigonum sternocostale of the diaphragm, the A. thoracica interna becomes the A. epigastrica superior. The A. epigastrica inferior derives from the A. iliaca externa.
* clinical term: A. mammaria interna
** clinical term: V. mammaria interna
Lymph vessels
Fig. 2.111 Superficial lymph vessels and regional lymph nodes of the ventral wall of the trunk.
The axillary lymph nodes (Nodi lymphoidei axillares, including the Nodi lymphoidei brachiales and pectorales) collect the lymph of the entire upper extremity, of large parts of the ventral wall of the trunk up to the watershed at the level of the umbilicus, as well as of the back up to the respective watershed (→ Fig. 2.112).
The superficial inguinal lymph nodes (Nodi lymphoidei inguinales superficiales) consist of a vertical and horizontal group. They collect the lymph of the entire lower extremity, of the ventral wall of the trunk up to the watershed at the level of the umbilicus, as well as of the external genitalia (including the penis), the perineal and anal region.
In women, the lymph vessels of the Corpus uteri and the uterotubal junction that pass through the inguinal canal with the Lig. teres uteri (→ Fig. 2.114) drain their lymph into the superficial inguinal lymph nodes.
In men, the lymph of the testis is drained to the para-aortal lymph nodes (not shown).
Fig. 2.112 Superficial lymph vessels of the posterior wall of the trunk.
Above the umbilicus, the lymph is drained into the axillary lymph nodes, whereas below the umbilicus the lymph is drained into the superficial inguinal lymph nodes.
Fig. 2.113 Superficial lymph vessels and regional lymph nodes of the female external genitalia as well as the perineal and anal region; caudal view.
The lymph of external genitalia, perineum, and anal regions drains into the superficial inguinal lymph nodes. Initial lymphatic stations are the Nodi lymphoidei inguinales superficiales superomediales.
Fig. 2.114 Superficial and deep lymph vessels and regional lymph nodes of vagina, Vagina, uterus, Uterus, uterine (FALLOPIAN) tube, Tuba uterina, and ovary, Ovarium; ventral view.
• The lymph of the upper two thirds of the vagina is drained into the pelvic lymph nodes, the lower third drains into the inguinal lymph nodes.
• The lymph from the ovary, the FALLOPIAN tube, and part of the uterine fundus and corpus is drained alongside the A. ovarica, located in the Lig. suspensorium ovarii, into the Nodi lymphoidei lumbales.
• The second part of lymph from the uterine fundus, corpus, and cervix reaches the Nodi lymphoidei iliaci alongside the A. uterina.
• A third fraction of the uterine lymph from the fundus and corpus drains alongside the Lig. teres uteri into the Nodi lymphoidei inguinales superficiales (highlighted in yellow).
Innervation of the skin of the back
Fig. 2.115 Segmental innervation of the skin (dermatomes) and cutaneous nerves of the back; dorsal view.
Cutaneous nerves frequently receive nerve fibres from multiple spinal nerves, thus, the dermatome and the region of innervation of the cutaneous nerves differ. The dark blue line on the right indicates the demarcation between the innervation area of the Rr. posteriores (dorsales) and Rr. anteriores (ventrales) of the spinal nerves.
Topography, back
Vessels and nerves of the back
Fig. 2.116 Vessels and nerves of the back; dorsal view; superficial muscles and shoulder girdle were removed on the left side.
• vessels and nerves in the medial axillary space (triangular axillary space): A. and V. circumflexa scapulae (margins: cranial M. teres minor, caudal M. teres major, lateral Caput longum of the M. triceps brachii)
• vessels and nerves in the lateral axillary space (quadrangular axillary space): A. and V. circumflexa humeri posterior, N. axillaris (margins: cranial M. teres minor, caudal M. teres major, medial Caput longum of the M. triceps brachii, lateral humeral shaft)
• vessels and nerves in the triceps slit: A. and V. profunda brachii, N. radialis (margins: cranial M. teres major, medial Caput longum of the M. triceps brachii, lateral humeral shaft)
* vessels and nerves in the triangular axillary space
** vessels and nerves in the quadrangular axillary space
*** vessels and nerves in the triceps slit
Vessels and nerves of the neck
Fig. 2.117 Vessels and nerves of the occipital region, Regio occipitalis, posterior neck, Regio cervicalis posterior [(Regio nuchalis)], and upper region of the back; dorsal view.
Up to the scapular line, the skin of the back receives segmental innervation by the Rr. posteriores [dorsales] of the spinal nerves (Rr. cutanei posteriores). The N. occipitalis major from C2 and the N. occipitalis tertius from C3 (not shown) provide cutaneous innervation for the posterior neck and occipital region (Rr. mediales of the Rr. posteriores [dorsales]). The N. occipitalis minor derives from the Plexus cervicalis (Rr. anteriores [ventrales]) and is part of the Punctum nervosum (ERB’s nerve point). The course of the N. accessorius [XI] in the neck and shoulder region is also shown.
Fig. 2.118 Vessels and nerves of the occipital region, Regio occipitalis, and posterior neck, Regio cervicalis posterior; dorsal view.
To demonstrate the deep neurovascular tracts, the Mm. trapezius, sternocleidomastoideus, splenius capitis, and semispinalis capitis were detached and partially removed. On both sides of the posterior aspect of the neck the short neck muscles (Mm. recti capitis posterior minor and major as well as the Mm. obliqui capitis superior and inferior) are shown. These muscles create the margins of the vertebralis triangle (Trigonum arteriae vertebralis). Besides arteries and veins, the Nn. occipitalis major and suboccipitalis as well as the Nn. accessorii [XI] are shown.
Nerves of the neck and the deep posterior cervical region
Fig. 2.119 Nerves of the posterior neck, Regio cervicalis posterior; dorsal view.
The N. occipitalis major represents the R. posterior from C2 and projects into the occipital region. The R. posterior from C3 projects cranially as N. occipitalis tertius into the Lig. nuchae. Ascending from the vertebralis triangle, which harbours the A. vertebralis, the R. posterior from C1 innervates the short neck muscles as N. suboccipitalis.
Fig. 2.120 Vessels and nerves of the deep posterior neck, Regio cervicalis posterior, and content of the vertebral canal; dorsal view.
The vertebral canal was accessed from dorsal and the occipital bone is removed to view the Dura mater with opened Sinus sagittalis superior and Sinus transversus.
The ascending part of the A. vertebralis between the cervical vertebrae can be seen.
Cauda equina and lumbar puncture
Fig. 2.121 Vessels and nerves of the opened vertebral canal of the lumbar section of the vertebral column, Regio lumbalis; dorsal view.
Spinal nerve and Foramen intervertebrale
Fig. 2.123 Spinal nerve, N. spinalis, in the thoracic region; caudal view.
The stem of the spinal nerve is only a few millimeters long (Truncus nervi spinalis) and is created by the merger of the Radices anterior and posterior. The Truncus divides into the larger R. anterior (in the thoracic region as N. intercostalis) and the smaller R. posterior. The latter divides into a medial (R. medialis) and lateral (R. lateralis) branch which innervate the autochthonous muscles of the back (Mm. dorsi) and, with their terminal ends, provide cutaneous innervation of the back (Rr. cutanei medialis and lateralis). The R. communicans is the connection between the spinal nerve and the sympathetic trunk (Truncus sympathicus). The R. meningeus of the spinal nerve projects back into the vertebral canal and innervates the ligaments of the vertebral column and the meningeal membranes covering the spinal cord. The N. intercostalis runs along the underside of the rib (not shown) in a ventral direction, innervates the Mm. intercostales externi and interni, and provides Rr. cutanei lateralis and anterior for the innervation of the skin.
Fig. 2.124 Spinal nerve, N. spinalis, in the lumbar region of the vertebral column; view from the left side. [1]
Upon its passage through the Foramen intervertebrale, the spinal nerve divides into the Rr. anterior, posterior, meningeus, and communicans.
Fig. 2.125 Spinal nerve, N. spinalis, in the lumbar region of the vertebral column; sagittal section at the level of the Foramen intervertebrale; view from the left side. [1]
At the level of the Foramen intervertebrale the Radices anterior and posterior have not yet merged to form the spinal nerve. They are still surrounded by the Dura and immersed in cerebrospinal fluid. Shown are the ventrally located Discus intervertebralis and the dorsally located Lig. flavum with the adjacent zygapophyseal joint.
Spinal nerve
Fig. 2.126 Nerves of the vertebral column, Columna vertebralis; view from the right side in an oblique angle.
Branches of the spinal nerve are shown which project to adjacent structures. These include the R. meningeus for the sensory innervation of the meningeal membranes of the spinal cord, smaller branches derived from the R. posterior for the Capsula articularis of the zygapophyseal joints, and the Rr. communicantes albus and griseus connecting with the Truncus sympathicus.
The R. communicans albus contains preganglionic sympathetic fibres from the lateral column of the spinal cord for the Truncus sympathicus. The R. communicans griseus contains postganglionic sympathetic fibres of the sympathetic trunk which project back to the spinal nerve. Autonomic nerve fibres from the sympathetic trunk innervate the Disci intervertebrales and ligaments of the vertebral column.
Fig. 2.127 Structure of a spinal nerve, N. spinalis, and spinal cord segment, exemplified by two thoracic nerves, Nn. thoracici; oblique superior view.
Each spinal nerve is composed of an anterior root (Radix anterior) and a posterior root (Radix posterior). The cell bodies (perikarya) of motor nerve fibres are located in the grey matter of the spinal cord and exit through the anterior root; the perikarya of sensory nerve fibres are located in the dorsal root ganglion (Ganglion sensorium nervi spinalis) and the fibres enter the spinal cord via the dorsal root. Rr. communicantes connect the spinal cord with the chain of ganglia of the Truncus sympathicus (Ganglion trunci sympathici). The dorsal branches of the spinal nerves are arranged in a segmental order; with the exception of the intercostal nerves 2 to 11, the other ventral branches create plexus.
Blood vessels and nerves of the vertebral canal
Fig. 2.128 Content of the vertebral canal, Canalis vertebralis; cross-section at the level of the 5th cervical vertebra; cranial view.
The spinal cord is surrounded by the Dura, the Arachnoidea and the Pia mater spinalis and immersed in cerebrospinal fluid in the subarachnoid space (Spatium subarachnoideum). In the vertebral canal, this dural tube and the exiting roots of the spinal nerves are surrounded and protected by adipose tissue with embedded venous plexus (Plexus venosus vertebralis internus anterior and posterior) and nourishing blood vessels.
See epidural anaesthesia → page 331, Vol. 3.
Fig. 2.129 Content of the vertebral canal, Canalis vertebralis; cross-section at the level of the 3rd lumbar vertebra; cranial view.
Below the 1st/2nd lumbar vertebra and before exiting the vertebral canal, nerve roots from L2 onwards, including the N. coccygeus, run caudally as a loose bundle of fibres surrounded by the dural sac. This entire collection of nerve roots is named Cauda equina. Located in between the nerve fibres and originating from the Conus medullaris of the spinal cord is the thin and thread-like Filum terminale.
See lumbar puncture → pages 109 and 331, Vol. 3.
Vessels and nerves of the vertebral canal
Fig. 2.130 Thoracic region of the vertebral column with spinal cord, Medulla spinalis, and sympathetic trunk, Truncus sympathicus; ventral view.
The Spatium epidurale is shown which surrounds the vertebral canal with its meninges. It contains the Plexus venosus vertebralis internus anterior and the Rr. spinales of the A. intercostalis posterior embedded in adipose tissue. The A. spinalis anterior runs on top of the spinal cord.
Fig. 2.131 Veins of the vertebral canal, Canalis vertebralis; view from the right side in an oblique dorsal angle.
The vertebral canal is filled with a dense network of veins which form the Plexus venosi vertebrales interni anterior and posterior. Located in the Spatium epidurale, this venous plexus covers the meninges which surround the spinal cord and the Cauda equina. The two plexus are connected with the Plexus venosus vertebralis externus posterior via Vv. intervertebrales. The latter plexus drains the blood (in the lumbar region of the vertebral column) into the paravertebral Vv. lumbales ascendentes (in the thoracic region of the vertebral column run the Vv. azygos, hemiazygos, and hemiazygos accessoria). These veins also collect blood from the Plexus venosus vertebralis externus anterior which drains the anterior side of the vertebral bodies and the intervertebral discs.
Overview and development
Fig. 2.134 Milk line.
The development of the mammary gland initiates in the milk line (mammary ridge), a strip of thickened surface ectoderm formed in embryonic week 6 that extends from the axillary pit to the inguinal region. With the exception of the area above the M. pectoralis major, the location for the development of the future breast (Mamma), the rest of the milk line normally regresses.
Female breast
Female breast
Fig. 2.135 Breast, Mamma; ventral view.
The breast is composed of the mammary gland (Glandula mammaria) and a fibrous stroma filled with adipose tissue. The breast has up to 20 individual glands (Lobi), each possessing a separate efferent lactiferous duct opening onto the mammary nipple (Papilla mammaria).
The branched lactiferous ducts terminate in groups of alveoli (Lobuli). During pregnancy, the glandular tissue transforms into the lactating breast.
* clinical term: COOPER’s ligaments
Blood supply and lymphatic drainage
Fig. 2.137 Blood supply of the female breast, lymphatic drainage passages of the female breast, and location of regional lymph nodes.
The approximately 40 axillary lymph nodes do not just filter the lymph of almost the entire upper extremity but also collect two thirds of the lymph from the Mamma and the major part of the lymph fluids derived from the thoracic and upper abdominal wall. The Truncus subclavius collects the lymph of the axillary lymph nodes and drains it into the Ductus lymphaticus dexter and the Ductus thoracicus (not shown) on the right and left side, respectively.
* clinical term: ROTTER’s lymph nodes
Clinic
Fig. 2.138 Radiograph of the Mamma (mammography) of a 47-year-old woman.
Mammography is a radiological examination used for the early diagnosis of mammary carcinoma, the most frequent tumour in women.
Fig. 2.139 Radiograph of a Mamma (mammography) of a 23-year-old woman. [19]
Normal mammary parenchyma shows poorly demarcated white condensations primarily located beneath the region of the nipple (Mammilla). In young women, breast tissue can be extremely dense due to scarcely distributed adipose tissue.
Innervation of the skin of the thoracic and abdominal wall
Fig. 2.142 Segmental sensory innervation of the ventral thoracic and abdominal wall (dermatomes).
Skin regions receiving sensory fibres from a single spinal nerve are named dermatomes. The mammilla is located within dermatomes T4 to T5; the umbilicus is located in dermatome T10.
Fig. 2.143 Segmental sensory innervation of the thoracic and abdominal wall.
On the right side, the spinal nerves responsible for the innervation of the dermatomes are shown (→ Fig. 2.142).
HEAD’s zones represent skin areas which refer to distinct viscera as a result of cross-connections between the somatic and autonomic nervous system in a corresponding spinal cord segment. These cross-connections of the somatic and autonomic nervous system are due to the segmented (metameric) body structure. HEAD’s zones for referred pain relate to specific inner organs. The HEAD’s zone of a specific organ can stretch across multiple dermatomes but has a specific point of maximal reflex.
Topography, abdomen and abdominal wall
Vessels and nerves of the trunk
Fig. 2.144 Epifascial and deep vessels as well as nerves of the ventral wall of the trunk of a woman; ventral view.
On the right side of the body, the Fasciae deltoidea, pectoralis, thoracica, abdominis, and lata with their epifascial neurovascular structures and the mammary gland are shown. The Mamma receives its blood supply from the Rr. mammarii mediales of the A. thoracica interna and from the Rr. mammarii laterales of the Aa. thoracica lateralis and thoracodorsalis.
On the left side of the body, the superficial fascia was removed to provide a clear view of the muscles. The rectus sheath is opened, the M. rectus abdominis is cut in the middle; its parts are folded up- and downward. On the posterior aspect of the M. rectus abdominis the Vasa epigastrica superior and inferior are seen.
* clinical term: A. mammaria interna
Relief of the inside of the ventral abdominal wall
Fig. 2.145 Ventral abdominal wall of a newborn; inside view.
The descensus of the testis into the scrotum is completed in a mature newborn.
Extending across the Anulus inguinalis profundus, the Proc. vaginalis peritonei of the Peritoneum parietale descends slightly into the inguinal canal.
Fig. 2.146 Ventral abdominal wall; inside view.
The Fossa inguinalis medialis, Fossa inguinalis lateralis, Lacuna vasorum, and Lacuna musculorum are shown. To demonstrate the neurovascular passage ways, the Peritoneum parietale and the Fascia transversalis were removed on the right side of the body.
* clinical term: HESSELBACH’s ligament
** clinical term: HESSELBACH’s triangle
Inguinal canal
Fig. 2.147 Superficial inguinal ring, Anulus inguinalis superficialis; ventral view.
The Crus mediale and Crus laterale as part of the aponeurosis of the M. obliquus externus abdominis and interconnecting Fibrae intercrurales constitute the margins of the superficial inguinal ring. The caudal margin is the Lig. reflexum as part of the Lig. inguinale.
On the right side of the body, the aponeurosis of the M. obliquus externus abdominis was reflected and provides a clear view on the M. obliquus internus abdominis. Muscle fibres of the M. obliquus internus abdominis split off as M. cremaster and, as a superficial muscle layer, accompany the Funiculus spermaticus into the scrotum.
Fig. 2.148 Walls and content of the inguinal canal, Canalis inguinalis, right side; ventral view. [1]
The inguinal canal is confined by the aponeurosis of the M. obliquus externus abdominis in the front, caudally by the Lig. inguinale, posteriorly by the Fascia transversalis, and cranially by the free margin of the M. transversus abdominis.
Fig. 2.149 Inguinal canal, Canalis inguinalis, and spermatic cord, Funiculus spermaticus, right side; ventral view. [10]
The approximately 4–6 cm long inguinal canal penetrates the ventral abdominal wall above the inguinal ligament in an oblique angle from a posterior-lateral-cranial to an anterior-medial-caudal direction. The inner opening is the Anulus inguinalis profundus which is formed by the Peritoneum and Fascia transversalis as the posterior demarcation and by the M. transversus abdominis and Lig. inguinale as cranial and caudal margins, respectively. The outer opening is the Anulus inguinalis superficialis with the aponeurosis of the M. obliquus externus abdominis and the Lig. inguinale (Lig. reflexum) being the anterior and caudal margins, respectively. Located in the inguinal canal is the Funiculus spermaticus. On its Fascia spermatica externa, the N. scrotalis anterior of the N. ilioinguinalis reaches the anterior part of the scrotum. Like the M. transversus abdominis, the M. obliquus internus abdominis is positioned superior to the Funiculus spermaticus and contributes muscle fibres (M. cremaster) that cover the Funiculus spermaticus. The M. cremaster has its own fascia (Fascia cremasterica), reaches onto the testis between Fasciae spermaticae externa and interna, and plays an important role in regulating the temperature for spermatogenesis to occur.
* transversus tendinous arch
** clinical term: GIMBERNAT’s ligament
Fig. 2.150 Content of the spermatic cord, Funiculus spermaticus, and coverings of testis, left side; ventral view. [10]
Covered by the Fascia spermatica externa, the M. cremaster, and the Fascia spermatica interna, the spermatic cord contains the Ductus deferens, the A. ductus deferentis, the A. testicularis (a direct branch of the Aorta), the Plexus pampiniformis (drains into the V. testicularis and from there on the right side into the V. cava inferior and on the left side into the V. renalis), the R. genitalis of the N. genitofemoralis, and the Vestigium processus vaginalis (obliterated Proc. vaginalis testis which guided the testicular descent from the abdominal cavity into the scrotum, → Fig. 2.151).
The testis is covered by the serous Lamina visceralis (epiorchium) and the Lamina parietalis (periorchium) which are separated from each other by a gap, the Cavum serosum scroti. Epiorchium and periorchium are connected at the mesorchium. The other coverings listed from the inside to the outside are the Fascia spermatica interna, muscle fibres of the M. cremaster with Fascia cremasterica, and the Fascia spermatica externa. Both testes reside in the scrotum (not shown) which contains the protective dartos fascia (Tunica dartos). Myoepithelial cells in the Tunica dartos cause the scrotum to contract, a process involved in testicular thermoregulation and important for normal spermatogenesis to occur.
Development of the inguinal canal
Fig. 2.151 Descensus testis from week 7 (post conception) until birth.
In the male fetus, the testes are relocated during the fetal period from the abdominal cavity along the Gubernaculum testis and beneath the Peritoneum parietale of the dorsal abdominal wall into the scrotum. The Peritoneum parietale creates an invagination (Proc. vaginalis peritonei) that stretches from the inguinal canal into the scrotum and becomes positioned superior to the testis. With the exception of a remnant on the testis (Tunica vaginalis testis), the Proc. vaginalis peritonei obliterates shortly after birth.
Inguinal hernias
Fig. 2.152 Structure of the ventral abdominal wall and the coverings of the spermatic cord, Funiculus spermaticus, and testis, Testis; schematic diagram. For didactic reasons, the inguinal canal, the spermatic cord, and the scrotum are drawn in the same plane. (according to [1])
The Descensus testis causes the testis to lie in a pouch of the abdominal wall which extends into the scrotum. Therefore, scrotum and spermatic cord possess the same structure as the abdominal wall.
The Fascia of the M. obliquus externus abdominis continues as Fascia spermatica externa onto the Funiculus spermaticus. Beneath lies the M. cremaster which splits from the M. obliquus internus abdominis and is covered by the Fascia cremasterica. The next deeper layer contains the Fascia spermatica interna as part of the aponeurosis of the M. transversus abdominis which covers the content of the Funiculus spermaticus. With the exception of a remnant in the testicular region (Tunica vaginalis testis with Lamina parietalis = periorchium and Lamina visceralis = epiorchium), the Proc. vaginalis peritonei is obliterated and has become the Vestigium processus vaginalis (a fibrous cord; left side of the image). On the right side of the image, the Proc. vaginalis testis failed to close but persists (Proc. vaginalis peritonei persistens) and, thus, causes an open connection between the abdominal cavity and the Cavitas serosa scroti.
Fig. 2.153 Inguinal hernias; schematic drawing. Left side of the image: lateral, indirect hernia; right side of the image: medial, direct hernia. (according to [1])
Indirect inguinal hernias enter the inguinal canal in the Fossa inguinalis lateralis through the Anulus inguinalis profundus.
Direct inguinal hernias penetrate through the muscle-free Trigonum inguinale (HESSELBACH’s triangle) in the Fossa inguinalis medialis which is a weak spot in the ventral abdominal wall. Here, the posterior abdominal wall consists only of the Fascia transversalis and the Peritoneum parietale (Paries dorsalis tenuis canalis inguinalis).
* intestinal loop in hernial sac
** peritoneal cavity
*** newly formed peritoneal hernial sac
Plexus lumbosacralis
Fig. 2.154 Posterior abdominal wall with Plexus lumbosacralis; ventral view.
The Plexus lumbosacralis is composed of the Plexus lumbalis (T12, L1–L3 [L4]) and the Plexus sacralis ([L4] L5, S1–S5). The Plexus lumbalis is important for the innervation of the wall of the trunk. Shown are the segmental organization and the course of the Rr. anteriores [ventrales] of the spinal nerves of the Plexus lumbalis which innervate the abdominal muscles, the inguinal region, and the thigh. These are from cranial to caudal the Nn. subcostalis (intercostalis XII), iliohypogastricus (T12, L1), ilioinguinalis (L1), genitofemoralis (L1, L2) with R. femoralis and R. genitalis, and the N. cutaneus femoris lateralis (L2, L3). The N. femoralis (L1–L4) exits the vertebral column and, when completing its passage through the Lacuna musculorum, provides Rr. cutanei anteriores for the innervation of the skin of the thigh. Also shown is the N. obturatorius ([L1] L2–L4) entering the Canalis obturatorius.