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

DORSOLATERAL GROUP

Complex muscle

• This is a single muscle situated on the dorso-lateral aspect of the leg.
• Origin: By a strong tendon from the extensor fossa of the femur.
• This shows about its middle three muscular bellies, each of which is succeeded by a tendon.
  • The peroneus tertius is the most superficial part and well developed. It is located in front and partly internal to the other two bellies. It is succeeded by a strong flat tendon, which is perforated by the tibialis anterior. It is inserted to the tubercle at the dorso-medial aspect of the proximal extremity of the large metatarsal bone. It is provided with a synovial sheath at the tarsus.
  • The long digital extensor (extensor digital longus) is lateral to the preceding. It is succeeded by a tendon, which behaves like the tendon of common digital extensor of the forelimb. The tendon is inserted into the extensor process of the third phalanx.
  • The third division is the medial digital extensor and is under cover of the preceding two divisions. Is succeeded by a tendon, which resembles that of the forelimb in its course and terminations. The long and medial digital extensor has a common synovial sheath at the tarsus.
• Action: To flex the hock and extend the digits.
• Blood supply: Anterior tibial artery.
• Nerve supply: Deep peroneal nerve.

Tibialis anterior (Tibialis anticus)

• This is a thin, triangular muscle lies under the cover of the complex muscle on the lateral surface of the tibia and arises by two heads.
• Origin:
  • Tuberosity of the tibial crest;
  • Upper part of the lateral border of the tibia and the fibrous cord of the fibula. Its tendon passes through the tendon of the peroneus tertius. Its tendon is provided with a synovial sheath at the tarsus.
• Insertion: The postero-medial surface of the upper extremity of the large metatarsal and the second and third tarsal bones.
• Action: To flex the hock.
• Blood supply: Anterior tibial artery.
• Nerve supply: Deep peroneal nerve.

Peroneus longus

• The muscle is situated between the peroneus tertius and lateral digital extensor.
• Origin: Lateral condyle of the tibia and the fibrous cord of the fibula.
  • The tendon crosses over the tendon of lateral digital extensor, passes under the lateral ligament passes through a bony groove formed between the tarsal bones and the large metatarsal. It is provided with a synovial sheath at the tarsus.
• Insertion: To the first tarsal and proximal end of the large metatarsal bone.
• Action: To rotate the hock inwards.
• Blood supply: Anterior tibial artery.
• Nerve supply: Deep peroneal nerve

Lateral digital extensor (Extensor digitalis lateralis)

• This is situated lateral to the preceding.
• Origin: Lateral ligaments of the stifle and the lateral condyle of the tibia.
  • The muscle is succeeded by a tendon, which passes through a synovial sheath in common with that of the preceding muscle, crosses under that tendon and thereafter, it resembles the tendon of the muscle of the forelimb in its course and termination. It is provided with a synovial sheath at the tarsus.
• Blood supply: Anterior tibial artery.
• Nerve supply: Superficial peroneal nerve.

Extensor digitalis brevis (Short extensor)

• This is a narrow muscle situated on the dorsal surface of the metatarsus.
• Origin: A depression on the dorsal surface of the metatarsus.
• Insertion: Tendon of long digital extensor.
• Action: To assist the long digital extensor.
• Blood supply: Anterior metatarsal artery.
• Nerve supply: Deep peroneal nerve.