Question

LABORATORY 1 REPORT VERTEBRAL COLUMN AND RIB CAGE

1. Make a drawing of a cervical vertebra, showing the important structures studied in this exercise.

   Label the parts and indicate the main function of each.

2. What evidence can you find that the axial skeletons of higher vertebrates have homologous parts? What inferences would this lead scientists to conclude?

3. Explain how the spinal curvatures of the adult differ from that of the fetus. Make a sketch illustrating these curvatures.

4. Describe the state of development of the vertebrae, spinal column and rib cage of humans at time of birth. Explain how this is adaptive.

Answer 1

Vertebral column in general
The vertebral column usually consists of 33 vertebrae: 24 presacral vertebrae (7 cervical, 12 thoracic, and 5 lumbar) followed by the sacrum (5 fused sacral vertebrae) and the coccyx (4 frequently fused coccygeal vertebrae). The 24 presacral vertebrae allow movement and hence render the vertebral column flexible. Stability is provided by ligaments, muscles, and the form of the bones. The abbreviations C., T., L., S., and Co. are used for the regions, and these are sometimes followed by V. for vertebra or N. for nerve.
Curvatures.
The adult vertebral column presents four anteroposterior curvatures: thoracic and sacral, both concave anteriorly, and cervical and lumbar, both concave posteriorly . The thoracic and sacral curvatures, termed primary, appear during the embryonic period proper, whereas the cervical and lumbar curvatures, termed secondary, appear later (although before birth) and are accentuated in infancy by support of the head and by the adoption of an upright posture.
Parts of a Vertebra.
A typical vertebra consists of (1) a body and (2) a vertebral arch, which has several processes (articular, transverse, and spinous) for articular and muscular attachments. Between the body and the arch is the vertebral foramen: the sum of the vertebral foramina constitutes the vertebral canal, which houses the spinal cord . In addition to the transverse and spinous processes, which serve as short levers, the 12 thoracic vertebrae are connected by joints with paired, long levers, namely the ribs.
The bodies of the vertebrae are separated from each other by intervertebral discs. The body is mainly spongy bone and red marrow, but the margins of the upper and lower surfaces consist of a ring of compact bone, the vertebral end-plates. The body is marked on its sides by vascular foramina.
The vertebral arch consists of right and left pedicles (which connect it to the body) and right and left laminae. The transverse processes emerge laterally at the junction of the pedicles and laminae, and the spinous process proceeds posteriorly from the union of the laminae. The superior and inferior articular processes project vertically from the vertebral arches on each side and bear articular facets. When vertebra are in their anatomical position, notches between adjacent pedicles form intervertebral foramina, each of which typically transmitsneural structures including a spinal ganglion and a ventral root of a spinal nerve.
Relationship of Spinal Nerves to Vertebrae.
The first cervical nerve emerges between the skull and the atlas, and cervical nerves C2 to 7 continue to leave the vertebral canal above the correspondingly numbered vertebrae. C8 emerges between the C7 and T1 vertebrae, and the remaining spinal nerves leave below the correspondingly numbered vertebrae.
Regional characteristics of vertebrae
The vertebrae of each region have special characteristics, which are now described.
Cervical Vertebrae.
The seven vertebrae of the neck are characterized by an opening in each transverse process known as a foramen transversarium. The upper six pairs of foramina transversaria transmit the vertebral artery. The C1 vertebra, which supports the skull, is termed the atlas, and C2, which serves as a pivot for the atlas, is termed the axis.
Atlas. The atlas (C1), which has neither body nor spinous process, consists of two lateral masses connected by a short anterior and a longer posterior arch. Each lateral mass presents upper and lower facets, for the occipital condyle of the skull and for the axis, respectively. The transverse processes are long and are vaguely palpable in vivo immediately below the auricle. The anterior arch presents an anterior tubercle in front (for the anterior longitudinal ligament) and a facet posteriorly (for the dens of the axis). The posterior arch is grooved above for the vertebral artery and the C1 nerve on each side, and it presents a posterior tubercle.