Overview
The number of caudal vertebrae varies between cats; it is usually about twenty. They articulate with the apex of the sacrum and with each other through intervertebral discs, which makes the tail very mobile. The tail helps with balance during jumping and walking on narrow surfaces, and it is a means of communication.
Key features
- First caudal vertebrae: complete vertebral arch with a vertebral canal (containing only the last nerve roots, 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 tubercles, leaving a cylindrical body that is longest in the middle of the tail and progressively shorter towards the tip.
- Haemal arches (arcus haemales): small V-shaped bones on the ventral side of the first caudal vertebrae; they protect the median caudal artery that runs along the ventral surface of the tail.
Clinical relevance
- Sacrocaudal luxation and fractures after tail pull or road accidents: injury to the caudal, pudendal and pelvic nerves causes a flaccid tail and urinary or faecal incontinence.
- Scottish Fold osteochondrodysplasia: the same cartilage defect that folds the ears shortens and thickens the caudal vertebrae; a stiff, inflexible tail is an early sign.
- Manx cats: taillessness caused by a dominant mutation is associated with sacrocaudal malformations and spina bifida (Manx syndrome).
- Tail vaccination: the distal tail is used as a vaccine injection site because, if an injection-site sarcoma develops, it allows amputation with wide margins.
This model has 17 caudal vertebrae, a number set by the skeletal reconstruction.