Fetal Pig Anatomy (1961)

biology students have a special interest in the study of the fetal pig because it's anatomy and the anatomy of man are very similar this uterus contains fetal pigs which are representative of those commonly used for the study of mammalian anatomy cutting the wall of the uterus reveals that the fetal pigs are enclosed in membranes the outer membranes and the lining of the uterus are in close association with each other and together form the placenta cutting the outer membranes and laying them back exposes an inner sac containing a watery fluid this fluid cushions the fetus against shock puncturing the sac allows the fluid to escape and laying the sac aside shows the umbilical cord which connects the fetus with the placenta we will now examine this larger fetal pig whose Anatomy is very similar to your own cutting the angle of the jaws permits a clear view of the mouth cavity the roof of the mouth cavity consists of the bony hard palate and the fleshy soft palate behind the tongue is the respiratory opening or glottis which is covered by the epiglottis when swallowing behind the glottis is the opening to the esophagus removing the soft palate shows the two openings of the eustachian tubes each tube connects the throat to a middle ear next the organs in the abdomen will be examined after tying the fetal pig to the dissecting tray an incision is made around the umbilical cord when the incision is completed the umbilical vein is cut and the cord is laid back additional incisions completely expose the abdominal cavity the muscular diaphragm separates the abdominal cavity from the thoracic cavity smooth membranes line the abdominal cavity and cover the abdominal organs the most obvious organs in the abdomen are the lobed liver the stomach the spleen the small intestine the large intestine or colon and the urinary bladder now the organs of the digestive system will be examined food taken in the mouth enters the esophagus muscular contractions of the esophagus move the food to the stomach where early stages of digestion take place the partly digested food passes from the stomach through the muscular pyloric valve and enters the first part of the small intestine the duodenum here the food is mixed with secretions from the liver and pancreas the liver secretes bile which is stored and concentrated in the gall bladder when needed the bile flows from the gall bladder through a duct to the duodenum the pancreas lies under the stomach and secretes several digestive enzymes which pass into the duodenum the long small intestine also secretes enzymes and accounts for most digestion and absorption of the food the undigested food enters the large intestine water is absorbed from the food as it passes through the large intestine the waste material continues through the rectum and out the anus be examined the two kidneys remove organic wastes excess water and salts from the bloodstream and excrete these waste materials as liquid urine through the ureters the urine passes through the ureters to the urinary bladder the bladder stores the urine until it is expelled through the single urethra this specimen is a female and these two ovaries are part of its reproductive system the ovaries produce eggs which are fertilized in the fallopian tubes and then are transported to the uterus where the embryos mature the vagina extends from the uterus the vagina and the urethra join in a common chamber which opens to the exterior we now will examine the reproductive system of a male each of its two scrotal sacs contains at Estus in which sperm developed a sperm duct extends from each testa's and joins the single urethra the urethra passes through the penis to the exterior next the organs in the neck and thoracic cavity will be examined the most obvious organs in the thoracic cavity are the heart and the two lungs the thymus gland is also prominent it extends from the neck into the thoracic cavity this is the thyroid gland which plays an important part in the control of metabolism smooth pleural membranes lie in the thoracic cavity and cover the lungs a cyclic membrane the pericardium encloses the heart removing the pericardium permits a better view of the heart the heart has four chambers which is characteristic of all mammals the two upper chambers are the thin walled Oracle's which receive blood from all parts of the body and the two lower chambers are the thick muscular ventricles which pump the blood to all parts of the body this is one of the coronary arteries which supply blood to the tissues of the heart we will examine the circulation of the blood as it occurs after the mammal is born the right ventricle pumps the blood through the pulmonary trunk and pulmonary arteries to the lungs here carbon dioxide is exchanged for oxygen then the oxygenated blood flows through the pulmonary veins and enters the left auricle the left ventricle pumps the oxygenated blood through the large systemic truck from which branches are distributed these are some of the branches which supply the upper part of the body the descending aorta passes through the diaphragm and branches in the lower part of the body for example these arteries supply blood to the stomach spleen and liver the renal arteries supply blood to the kidneys in the fetus there are large umbilical arteries these extend through the umbilical cord to the placenta Blood returns to the heart through the systemic veins the large posterior vena cava receives blood from all parts of the lower body regions for example the renal veins empty blood from both kidneys into the posterior vena cava the portal vein carries blood from the digestive tract to the liver in the fetus blood from the placenta flows through the umbilical vein which also enters the liver all blood entering the liver leaves by way of the posterior vena cava which penetrates the diaphragm and enters the right oracle blood from many veins of the upper body regions empties into the anterior vena cava which also enters the right oracle the right ventricle then pumps the blood out the pulmonary trunk to the lungs however in the fetus most of the blood is not pumped to the lungs but passes through the short ductus arteriosus directly to the aorta removing some of the blood vessels and the heart permits a clearer view of the respiratory system after the mammal is born air passes into the larynx which contains the vocal chords and continues through the flexible trachea which is supported by rings of cartilage the trachea branches into the two bronchi which extend to the lungs each bronchus subdivides many times to form a branch work of small tubes these tubes terminate in small bulbs where exchange of gases with the blood occurs in order to examine parts of the nervous system the skin overlying the brain and spinal cord is removed the protective skull and vertebral column are also removed exposing the central nervous system the central nervous system consists of the brain and the spinal cord membranes cover the delicate brain and the spinal cord certain parts of the brain are visible the two olfactory lobes the cerebrum which is mostly concerned with conscious activities the cerebellum which is necessary for balance and muscle coordination and the medulla oblongata which controls many involuntary actions such as breathing and heartbeat the medulla oblongata is continuous with the spinal cord many spinal nerves arise from both sides of the spinal cord the spinal nerves branch and extend to all parts of the body through careful study of the anatomy of a mammal such as the fetal pig you will learn about the anatomy of all mammals including yourself