Digestive System The stomach is the large, sack-like organ lying just below the liver. If you follow the stomach upwards, you will find where the esophagus passes through the diaphragm and joins to the stomach. With scissors, cut along the outer right curvature of the stomach. Open the stomach and note the texture of its inner walls. The ridges inside the stomach are called rugae, which expand and contract to allow for mechanical digestion. The stomach may not be empty because fetal pigs swallow amniotic fluid. Locate the top and bottom of the stomach. There are two sphincters (muscular rings) known as the cardiac sphincter (separates the esophagus and stomach) and pyloric sphincter (separates the stomach and small intestine). Both sphincters help control the movement of food through the stomach so that food does not pass along before it is properly digested. The soupy, partly digested food that enters the small intestine from the stomach is called chyme. Lift the stomach with your probe to locate the small, white pancreas. Pancreatic juice and bile, made by the liver and stored in the gall bladder, are added to the small intestine to continue chemical digestion. Inside the small intestine are many villi, the tiny projections that line the small intestine and increase the surface area for nutrient absorption. These nutrients are diffused from the small intestine and into the blood stream. Notice the small intestine is a coiled, narrow tube held together by a clear tissue called mesentery. The mesentery contains many blood vessels that diffuse nutrients absorbed by the villi into your body’s bloodstream. Follow the small intestine until it reaches the wider, large

intestine. The large intestine’s role it to absorb water from the chyme and return it to the body; this helps prevent dehydration. The large intestine leads into the rectum, a straight and terminal tube that runs along the back body wall and serves as a compacting station for feces. The rectum carries wastes to the opening called the anus, where it is eliminated. Answer the questions and label the diagram of the Digestive System on your Day 2 Study Guide. Complete Buddy Check!

Day 3 – The Abdominal Cavity

Urinary System

Lift or push aside the digestive organs to study the excretory organs that make up the urinary system. Locate the large, bean-shaped kidneys lying against the back body wall. Kidneys contain nephrons, which filter urea (cellular waste) from blood. Find the ureters, tubes which extend from each kidney to the bag-like urinary bladder. The urinary bladder temporarily stores urine (urea, salt, and water) filtered from the blood. Lift the urinary bladder to find the urethra, the tube which carries urine out of the body. Follow the urethra to the urogenital opening on the outside of the pig's body.

Day 4 – Thoracic Cavity

Examine the diaphragm, a sheet of muscle that stretches across the abdominal cavity and separates it from the thoracic cavity, where the respiratory and cardiovascular system located.

Respiratory System In order to see the upper part of the respiratory system, you will need to extend cut #1 up under the pig's throat and make lateral incisions in order to fold back the flaps of skin covering the throat. Locate the two, spongy lungs that surround the heart. The lungs of your fetal pig appear collapsed because they haven't been used for breathing; they have never contained air. Instead, the fetus received oxygen from the mother pig through its umbilical cord. Find the trachea, a large air tube that lies above the lungs. The trachea (or windpipe) is easy to identify because of the cartilaginous rings that help keep it from collapsing as the animal inhales and exhales. The trachea branches into each lung; these two tubes are called the left and right bronchi. Inside the lungs the bronchi branch into smaller bronchioles that end with a grape-like cluster of air sacs, or alveoli, where oxygen and carbon dioxide are exchanged through the capillaries. Resting on the top of the trachea, locate the pinkish-brown, bean-shaped structure called the thyroid gland. This gland secretes hormones that control metabolism. At the top of the trachea, find the hard, light-colored larynx or voice box. This organ contains the vocal cords that enable the animal to produce sound. Answer the questions and label the diagram of the Respiratory System on your Day 4 Study Guide. Complete Buddy Check!