Overview
The number of caudal (coccygeal) vertebrae varies between dogs and breeds, usually about twenty. They articulate with the apex of the sacrum and with each other through intervertebral discs, which makes the tail very mobile. Their length increases over the first vertebrae and then decreases steadily towards the tip.
Key features
- First caudal vertebrae: complete vertebral arch with a vertebral canal (containing only the last nerve roots of the cauda equina, not spinal cord), short spinous processes, well-developed transverse processes and cranial and caudal articular processes.
- Middle and distal vertebrae: the arch disappears and the processes are reduced to small cranial and caudal tubercles, leaving a cylindrical body.
- Hemal arches (arcus haemales): small V-shaped bones on the ventral side of the first caudal vertebrae; together with the ventral processes they protect the median caudal artery that runs along the ventral surface of the tail.
Clinical relevance
- Sacrocaudal luxation and fractures after trauma ("tail pull" injuries) can damage the caudal and pelvic nerves and cause loss of tail tone and urinary or faecal incontinence.
- Screw tail: hemivertebrae and fused caudal vertebrae in brachycephalic breeds produce a tightly curled tail and skin-fold dermatitis.
In this model the caudal vertebrae come from a CT scan of a greyhound, scaled to this skeleton and arranged in a hanging posture; the greyhound tail is relatively long.