Stomach

Stomach — This muscular pouch lies on the left side in the upper abdomen. It is the continuation of the esophagus. Find the esophagus and locate where it pierces the diaphragm to join the stomach. This is the cardiac end of the stomach. The fundus is the dilated anterior portion; the body is the main portion, while the pyloric region is the most posterior. This end joins the duodenum.

The cardiac sphincter controls the entrance of food into the stomach from the esophagus. The pyloric sphincter at the posterior end regulates the release of partially digested food (chyme) into the duodenum. Look along the inner walls of the stomach and note the rugae, or folds which help to churn and mix the food with digestive juices.

Mesenteries

The Mesenteries: make up the double layer extensions of the pericardium, they support most of the organs in the abdominal cavity. To locate the mesenteries, look for a layer of tissue that is lining the abdominal cavity. Some parts of the mesentery are attached to the organs to hold them in place.

Salivary Glands

To find the salivary glands, you must turn the fetal pig on its side first to get a better view of its cheeks. Then carefully cut through the skin along the side of the head between the ear and the mouth. Separate the skin from the underlying tissues and remove it to expose more of what is underneath. The platysma and other muscles associated with the skin are also removed to expose the salivary glands and ducts. This is to be don’t very carefully since the structure to be examined lie directly below the skin.

Parotid Gland — This is the largest of the salivary glands. It lies ventral to the pinna (external ear) and is recognized by its triangular shape and lobular texture. The parotid duct, can be seen emerging from the anterio-ventral edge of the gland by several roots. It then crosses the lower portion of the masseter muscle of the cheek, following the course of the prominent external maxillary vein. It continues to the mouth and opens opposite the upper fourth molar. You can find the opening by looking inside the cheek and tugging lightly on the duct with forceps.

Submandibular Gland — Most of this gland lies beneath and ventral to the parotid gland just posterior to the angle of the jaw. It is small and oval in shape. Separate the two glands. Its duct is hard to trace since it passes amongst some of the jaw muscles. It extends to the angle of the jaw, passes to the floor of the mouth, to the anterio-ventral connection of the tongue. At this point it opens into the mouth.

Sublingual Gland — This is the third salivary gland. It is flat and narrow and lies along the duct of the submandibular gland. Its duct parallels that of the submandibular and both open under the tongue, along its side.

The Digestive System

To examine the digestive system of the fetal pig, we cut down the center of the fetal pig, and around the umbilical cord. We made several horizontal cuts to make it easier to fold back the flaps of skin, to make the digestive system more accessible. Scissors are helpful when cutting through the ribs. Make sure to cut carefully and not too deeply, to avoid damaging the organs in the thoracic and abdominal cavity. 

Pull away the flaps of skin and muscle to expose the organs of the digestive system.

Video - Dissection Overview

Lets Take a Closer Look- this video shows an overview of the entire abdominal dissection pointing out the major parts included in it.

Muscles of Neck

Muscles of the Shoulder & Neck:

Acromiodeltoid: This is an elongated slender muscle extending over the anterior surface of the shoulder to the forelimb. To find this muscle you must expose the lateral surface of the upper forelimb and shoulder area by pulling back the skin first. Then toward the very top of the shoulder near the brachiocephalic, you must once again find the point of separation and break through it using the probe to separate out the muscle. Then find the other separation point about a half an inch below and break through it to isolate the muscle.

Masseter muscle: This is located on the neck of the pig slightly above the muscles of the throat. To locate this muscle, you do not have to do anything other than see where your previous throat muscles are located and look at the area slightly above them on either the left or right of the pig and there it is.

Muscles of Shank

Muscles of the shank:

The muscles of the shank are exposed once the skin is removed and can be identified once separated from one another.

Medial View of the Gastonemius:

Lateral View of the Gastronemious:

Gastronemius: This is the large muscle in the calf. To isolate this muscle, use your probe to remove all fat and connective tissue around the shank and lower hind leg so that you will be able to clearly see the separation points of the muscles in the area. On the lateral side, look for a separating point that runs vertically from the middle of the hind leg and break through it with your probe. This should go through to other side separating the muscle from the bone and other muscles attached to it.

Soleus: This muscle lies deep in the gastronemius. Once the gastronemius is isolated, look inside towards the middle of it for a separation point under the fat and connective tissue and break through once found. Keep breaking through the connective tissue to the other separation point to isolate. You may pull out (do not detach) the muscle for a better view if needed.

Tibialis anterior: This is the most ventral muscle of the shank and lies upon the tibia. Once the skin is removed this muscle is easily identifiable and is located at the front of the shank under the knee and above the ankle. Find the two separating points in the front under the fat and connective tissue and break through them to expose the wide muscle of the tibia.

This group of deeper muscles of the lower hind leg originates from the tibia and the distal end of the femur:

Extensor digitorum longus: This muscle is shaped like a narrow band and ends as a long, tough tendon. It is located beside the tibialis major and can be found by locating the edge of the muscle from the separation point between it and the tibialis and continuing to break the connective tissue from underneath to the next separating point from its neighboring muscle.

*Be sure not to rip the muscle off on the other hand as it does turn to a thin tendon on the bottom.

Peroneus longus: This muscle can be located beside the extensor digitorum longus and can be found in the same way as well. All you have to do is follow the separation point from the first side that has already been exposed all the way through to other with your probe separating out the muscle from the others.

Peroneus tertuis: This is the last of the deeper muscles of the shank located next to the peroneus longus. It can be found by locating the last separation point by breaking through the connective tissue and isolating the thin muscle.