VPB 121: Veterinary Physiology - II (2+1)

PROCEDURE

• Keep the pithed frog on its back on the dissection board.
• Cut the skin and abdominal muscles upto sternum and expose the abdominal viscera.
• Remove the liver, stomach, intestine and kidneys without touching the under lying sciatic nerve trunk emerging from the vertebral column passing to the hind limbs.
• Hold the vertebral column with a piece of cotton cloth and strip the skin off the legs with the help of another piece of cloth.
• Cut the vertebral column above the origin of the sciatic nerve. Discard the anterior portion of frog’s body.
• Separate the urostyle from the surrounding muscle and cut away its attachment with pelvic girdle.
• With the help of a bone cutter, longitudinally split the vertebral column into two equal halves .
• Cut the pelvic girdle carefully into two equal halves with a bone cutter . Preserve one of these legs in Frog Ringer’s solution.
• By holding the piece of vertebral column with forceps, isolate the sciatic nerve upto pelvic girdle.
• Observe the location of the triceps femoris, iliofibula, semimembranosus and small pyri­formis muscles on the dorsal aspect of the thigh.
• Make a small incision between the iliofibula and semimembranosus and carefully separate the muscles along the intermuscular groove and expose the sciatic nerve.
• Hold the stump of the vertebral column with a forceps gently raise the nerve and snipping off the lateral branches with the scissors without touching the main nerve.
• Nearing termination it divides into two branches and innervates the muscle at different levels. Both the branches should be preserved.
• Carefully separate the main branch of the sciatic nerve upto its insertion into the Gastrocnemius muscle.
• The nerve should never be touched with hands/ metallic objects.
• Separate Gastrocnemius muscle from the underlying tibia and ligate the tendoachilis at its centre point.
• Cut the tendoachilis well below the ligation. Then cut through the tibia just below the knee joint.
• Remove the thigh muscles and expose the femur bone and cut through femur about 1-1.5 cm of femur above the knee joint.
• Now the Gastrocnemius muscle and Sciatic nerve preparation is ready which consists of knee joint with portions of tibia and femur, then remove the thigh muscles and expose the femur bone and cut through femur about 1-1.5 cm of femur above the knee joint.
• Muscle nerve preparation consists of knee joint with portions of tibia and femur, the Gastrocnemius muscle and the Sciatic nerve with a piece of vertebral column.
• Appropriate electrical stimulus to the sciatic nerve, the Gastrocnemius muscle shows con­traction.