Materials / Reagents Required :

            10 % Neutral Buffered Formalin (NBF), Normal saline (10 litre), 70 % Ethanol (1 litre), different sizes of scissors, forceps, scalpel, spatula, bone cutter, cardboard paper, etc.

Safety Precautions :

            Protective equipments including laboratory coats, gloves, apron, etc., should be worn during euthanasia, necropsy as well as during the preparation of the solutions.

Procedure :

Anatomy :

Observe the following muscles of the head and throat muscles :

• Digastric muscle - a V shaped muscle that follows the lower jaw line and functions to open the mouth.
• Mylohyoid muscle runs at right angles to the longitudinal axis below the digastric muscle and functions to raise the floor of the mouth.
• Sternohyoid runs parallel to the longitudinal axis on either side of the midline and functions to pull the hyoid towards the sternum.
• Sternomastoid runs diagonally from the sternum to a point behind the ear and functions to rotate the head to one side (when one contracts), or rotates the head down (when both contract).
• Masseter / cheek muscle functions in mastication (chewing).

Observe the following chest and front leg (medial) muscles :

• Pectoralis Major is a large triangular muscle covering the upper thorax and functions to pull the arm towards the chest.
• Pectoralis Minor runs (a part) beneath the Pectoralis Major and dose the same function of Pectoralis Major.
• Biceps Brachii is a large muscle located on inside of the upper arm and functions to flex (bend) the lower arm.
• Epitrochlearis is a flat, thin muscle on the medial surface of the upper arm that functions to extend the lower arm.
• Flexors - the collection of small muscles on the medial surface of the lower arm and they function to flex the wrist and hand.

Observe the following muscles of the shoulder and lateral muscles of the front leg :

• Clavotrapezius - one of a group of three muscles that help to stabilize the scapula and its functionis to pull the clavicle forward.
• Latissimus dorsi  pulls the arm downward.
• Triceps brachii is a muscle with three heads and it runs between the scapula and humerus and the ulna. Its function is to extend the lower arm.

Observe the following hip and lateral muscles of the hind leg :

• Semitendinosus is located on the posterior margin of the leg and is partly hidden by the biceps femoris. Its function is to flex the lower leg.
• Gastrocnemius is the major 'calf' muscle on the posterior surface of the lower hind leg. Its function is to extend the foot.
• Soleus is located under the Gastrocnemius. Its function is to extend the foot.
• Tibialis Anterior is located on the anterior surface of the lower hind leg. Its functions is to flex the foot.

Observe the following hip and medial muscles of the hind leg :

• Gracilis is a flat muscle on the caudal (near the tail) portion of the inner thigh. Its function is to pull the thigh inward.
• Rectus femoris is located on the anterior (front) surface of the thigh. Its function is to extend the lower hind leg.
• Pectineus is located next to the femoral vein. Its function is to pull the thigh towards the body.

Observe the following abdominal muscles :

• External Oblique covers most of the ventral and lateral abdomen. Its function to compress and hold the internal organs in place.
• Rectus abdominis  runs parallel to the longitudinal axis of the body on either side of the linea alba. Its function is to compress and hold the internal organs.

Collection of the skin and muscle :

• After induction of anaesthesia/euthanasia, the fur of the animal shall be moistened with alcohol to prevent the fur from getting adhered into the tissue samples.
• Normal saline shall be kept ready during the necropsy to keep the lungs moist.
• The skin over the thoracic and abdominal cavities shall be opened with a median incision starting from the just above the penis in male rat and just above the urethral orifice in the female rat up to the neck region.
• Collect a piece of skin and place it over the cardboard and then fixed.
• Observe the presence of different muscles.
• The skeletal muscle shall be collected along with the sciatic nerve by excising and flipping over the thigh muscles. The sciatic nerve shall be placed on the cardboard paper, stapled and transferred to the fixative containing jar.