The vertebrae
The vertebral column is comprised of a number of bones arranged in a series along the midline of the bvertebrae and actng as a cushion'.
Regional variations
1. Cenical vertebrae I Fig.
3.1 1A). There are always seven cervical vertebrae in the neck of all ιnanιnιals. The Iirst cervical vertebra or atlas has a unique and distinctive shape. The atlas does not have a body or a spinous process, but consists of two large wing-like lateral masses joined by a ventral and dorsal arch. The second cervical vertebra or axis is also unusual and has an elongated blade-like spinous process, which serves as a point of attachment for neck muscles, A strong ligament, called the nuchal Iiffantent. also attaches to the spinous process and extends from the axis to the Iirst thoracic vertebra. On the cranial aspect of the axis, a projection of bone called the dens or odontoidprocess fits into the vertebral foramen of the atlas and serves as a pivot around which the atlas can be rotated. The remaining cervical vertebrae (C 3—C7) follow the basic vertebral plan, and get progressively smaller as they advance towards the junction with the thoracic vertebrae.2. Thoracic vertebrae (Fig 3.11 B). There arc usually 1 3 thoracic vertebrae. Their distinguishing feature is their tall spinous processes and short bodies. They articulate with the ribs at two sites: the costal fovea, which forms a synovial joint with the Iieadof the rib. and the transverse fovea, which forms a synovial joint with the tubercle of the rib. The height of the spinous processes decreases as the series progresses towards the lumbar region.
3. Lumbar vertebrae I Fig. 3.1 I C). There are usually seven lumbar vertebrae. These vertebrae have large bodies and long transverse processes angled Craiiiovciitrdllv. to which the lumbar muscles attach.
4. Sucral vertebrae (Fig. 3.1 ID). These three vertebrae are fused together to form the sacrum in the adult dog and cat. The sacrum forms a Iibrosynovial joint with the wing of the ilium of the pelvic girdle: the sacroiliac joint.
5. Caudal or coteι∣t∣eal vertebrae I Fig. 3.1 IE). These vary in number and shape according to the length of the tail. The Iirst few resemble the lumbar vertebrae, but they get progressively smaller and simpler throughout the series. The last few caudal vertebrae are reduced to little rods of bone.