VAN 121: Veterinary Gross Anatomy-II (2+2)

MUSCLES OF THE TAIL

• These muscles are situated around the tail enclosed in the strong coccygeal fascia.
• The movements of the tail are effected by five pairs of coccygeal muscles, three of which are longitudinally disposed around the coccygeal vertebrae and thus cover them completely.
• They are composed of series of fasciculi terminating into tendons.
• These muscles gradually diminish in their thickness as they are traced backwards.
• The coccygeal muscles are named as follows
• Sacro-coccygeus dorsalis (Erector coccygeus)
• Sacro-coccygeus lateralis (Curvator coccygeus)
• Sacro coccygeus ventralis (Depressor coccygeus)
• Intertransversales caudae
• Coccygeus
• Recto-coccygeus

• Three sacro-coccygeal muscles are distinguished by their position as dorsalis, lateralis and ventralis.

• Sacro-coccygeus dorsalis (Erector coccygeus)
• This muscle is situated on the dorsal aspect of the tail with its fellow on either side of the spines.
• Origin: The last three or four sacral spines and spines of some of the coccygeal vertebrae.
• Insertion: The upper faces of bodies of the coccygeal vertebrae, beyond the third.
• Action: To elevate the tail and to incline it laterally.
• Sacro-coccygeus lateralis (Curvator coccygeus)
• This muscle is situated lateral to the preceding. It is confounded at its anterior extremity with the multifidus dorsi
• Origin: The spinous process of the last lumbar and the transverse process of the sacral and the coccygeal vertebrae.
• Insertion: Lateral faces of the vertebrae, except the first three.
• Action: To elevate the tail and flex it laterally.
• Sacro coccygeus ventralis (Depressor coccygeus)
• This muscle is thicker than the dorsalis and situated on the ventral aspect of the tail. It consists of two parts, medial and lateral.
• Origin: Transverse process of fifth sacral vertebra.
• Insertion: Medial part is inserted to bodies of coccygeal vertebrae. Lateral part is inserted to bodies and transverse processes of coccygeal vertebrae.
• Action: To depress the tail.
• Intertransversales caudae
• These are situated in the lateral face of the tail between the lateralis and ventralis muscle. It extends from one vertebra to another and thus occupies the inter-transverse spaces.
• Origin: The lateral border of the sacrum and the transverse process of preceding coccygeal vertebra.
• Insertion: The transverse process of the first coccygeal and the transverse process of the vertebra behind.
• Coccygeus
• This muscle is thin, triangular situated against the lateral wall of the pelvis between the sacro-sciatic ligament and the rectum.
• Origin: Pelvic surface of the sciatic ligament, near the ischiatic spine.
• Insertion: The transverse processes of the second and third coccygeal vertebrae.
• Recto-coccygeus
• It is large band of plain muscle and detached on either side from the longitudinal layer of the muscular coat of rectum, to the fourth and fifth coccygeal vertebrae
• Action: To compress the anus, depress the tail over the perineum and flex the tail laterally.
• Blood supply: Middle and lateral coccygeal arteries.
• Nerve supply: Coccygeal nerves.

HORSE

• Resemble those of the ox in general.
• The coccygeus is less developed.

DOG

• Resemble those of the ox in general.
• These coccygeal muscles involve in the formation of pelvic diaphragm
• There is an additional sacro-coccygeus which arise on the edge of the sacrum, the transverse process of the first coccygeal vertebra and the posterior border of the ilium.
• The sacro-coccygeus arises from the lumbar vertebrae also.