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

METATARSUS AND DIGITS (PLANTAR ASPECT)

Dissection

Make a vertical incision of the skin on the posterior median line of the metatarsus joining the incision round the hock and fetlock and reflect the two flaps of skin to the sides. Make a vertical incision on the digits as on their dorsal aspect and reflect the skin flaps.

• Clean the nerves and vessels from the digital region upwards. While cleaning the flexor tendons feel with fingers, the synovia from the synovial sheath lining the rings for the two divisions of deep flexor tendon as in the forelimb.
• Slit the deep fascia along the medial border of the flexor tendons and secure the medial plantar nerve and artery.
• By slitting the deep fascia upwards and downwards, trace the nerve and the artery to their origin about and their termination below above the fetlock.
• The medial plantar nerve divides above the fetlock into the medial and lateral branches.
• The medial branch supplies a branch to the medial rudimentary digit and passed down in front of it as the medial plantar abaxial digital nerve on the medial face of the medial digit accompanied by the corresponding artery.
• The lateral branch runs round the flexor tendons, gains the interdigital space and joins the plantar of the deep peroneal nerve to form the plantar common digital nerve which divides into plantar proper digital nerves which run down the interdigital space of the digits.

Dissection

• By slitting the deep fascia along the lateral border of the flexor tendons secure the lateral plantar nerve and the artery.
• The artery is very fine.
• The nerve and the artery after their origin from the parent trunks pass obliquely outwards under the plantar ligament and descend along the lateral border of the flexor tendons.
• Get at the origin of the nerve and the artery on the medial aspect of the hock, carefully cut the plantar ligament across and follow them to the lateral border of the flexor tendons.
• Lateral plantar nerve: It gives a branch to the lateral rudimentary digit and passes down in front of it as the lateral abaxial digital nerve on the lateral face opf the lateral digit accompanied by the corresponding artery.
• Superficial flexor tendon: The single tendon above the fetlock has the same details as that in the metacarpus and hence the dissection should be made referring to the details thereunder.
• Deep flexor tendon: The tendon of the medial head joins the common tendon about the upper third of the metatarsus. The common tendon has the same details as in the metacarpus and hence the dissection should be made referring to the details thereunder.
• Suspensory ligament: Dissect by referring to the details given under the metacarpus.

Dissection

• Cut the suspensory ligament across its middle and reflect the parts apart to expose the plantar face of the metatarsus.
• Recognise the venous arches at the proximal and distal parts of the metatarsus. They overlie the minute arterial arches. Carefully remove the venous arches and their communicating veins.
• At the lower part of the metatarsus recognise the opening of the vascular canal from which two fine arteries diverge to the sides.
• In the canal is the perforating metatarsal artery to which converge two arteries from the plantar artery to form the distal plantar arch. Similarly on the upper part of the metatarsus recognise the venous arch and remove it.
• Recognise a fine artery descending from above, which is the perforating tarsal artery.
• It joins two branches from the sides contributed by their plantar to form the proximal plantar arch. From this arch a minute artery called deep plantar metatarsal artery descends to the distal arch.
• Now the dissector should cut the muscular attachments round the joints and study the ligament of the principal joints.

Note

• The plantar common digital artery arises from the distal plantar arch.
• Both the dorsal and plantar common digital arteries behave as the common digital arteries of the forelimb.
• So the dissection of the arteries may be made by referring to details given under the metacarpus and digits.