Brian McCauley 12/12/07 Page 1 of 1 Fetal Pig Anatomy Bio 6A/ Sanhita Datta Winter 2008 Last time, you explored some anatomical features of fish. Today, do the same with a mammal: the pig. The pigs we have are fetuses from the pork industry. They show all the standard mammalian features; they also still have an umbilical cord and some features of the circulatory system that are unique to fetuses. Web Links There are some excellent web sites showing fetal pig anatomy, and I borrowed pictures from some of them. Take a look at some of the links below. Bio 225 from Western Kentucky University, with good interactive graphics: http://bioweb.wku.edu/courses/biol225/images/Zoolab5b.htm Biodidac: a nonprofit site with lots of biology pictures; unlabeled. Photos in this handout are from biodidac. http://biodidac.bio.uottawa.ca/ Navigational Terms These terms help you understand where the various body parts are. • Dorsal: toward the back. • Ventral: toward the front (belly). • Anterior: toward the head. • Posterior: toward the tail. • Lateral: toward the side. • Medial: toward the center. External Anatomy Examine your pig externally before you begin your dissection. Locate and understand the functions of the following structures: • head • mouth • eyes • nose • vibrissae (whiskers) • neck • trunk • tail • thorax • abdomen • umbilical cord • umbilical vein/arteries • teats (nipples) • urogenital opening (males) • urogenital papilla (females) • anus • scrotal sac (males) Is it male or female? The genital organs on a fetal pig aren’t very obvious, but you can tell if your pig is male or female. Females have a urogenital papilla just below the anus. Males don’t have a urogenital papilla, but they do have a tiny urogenital opening just behind the umbilicalBrian McCauley 12/12/07 Page 2 of 2 cord. On males, you may also be able to see the beginning of a scrotal sac, visible as a swelling just ventral to the anus. Both males and females have nipples, just as in humans. Internal Anatomy The instructor will give you some suggestions on how to do the dissection. You should cut as little as possible. Once you open the body cavity, you will generally be able to separate the different organs by simply pulling them apart with your fingers, forceps, or a probe. The more you cut things up, the harder it will be to figure out what you’re looking at. Neck region Begin your dissection in the neck region. Cut midline on the ventral surface of the neck to expose the underlying muscles. Carefully separate the muscles to observe the underlying structures. Locate and understand the functions of the following structures: • larynx • thymus gland • thyroid gland • trachea • esophagus There are two big tubes running from the mouth into the body. The trachea carries air, and it is reinforced with cartilage so it doesn’t collapse. The esophagus carries food, and it is softer but more muscular than the trachea. The larynx is an enlarged structure on the trachea. If you cut it open, you can see the vocal cords inside. The thymus is an endocrine (hormone-secreting) gland that helps regulate the immune system. It’s a large, spongy structure covering the ventral surface of the trachea. kidneyliverurinarybladderumbilicushearttrachealargeintestinelungssmallintestinetestesstomachAnatomy OverviewBrian McCauley 12/12/07 Page 3 of 3 The thyroid is another endocrine gland; it’s a small bilobed structure just posterior to the larynx. The thyroid secretes hormones that help regulate metabolism. Thoracic cavity Vertebrates have true coeloms. In mammals, the coelom is divided into two main cavities: the thoracic cavity, which contains the lungs, and the abdominal (or peritoneal) cavity, which contains the digestive system. The thoracic cavity and the abdominal cavity are separated by the diaphragm, a sheet of muscle and connective tissue that helps in breathing. Note the many membranes lining the coelom and holding the organs in place. Look for these structures in the thoracic cavity: • lungs • heart heartsmallintestinediaphragmThoracic & Abdominal CavitiesliverlungsheartlungdiaphragmThoracic CavityliverBrian McCauley 12/12/07 Page 4 of 4 The lungs have several lobes. Note the how spongy the tissue is. The heart is muscular and easy to find. Note the aorta, where high-pressure blood leaves the heart on its way to the systemic circulation. You may also see the right and left carotid arteries, which supply blood to the head. For now, don’t spend too much time on the various lobes of the heart and the many blood vessels. Come back to this later. Abdominal cavity: digestive organs Locate and understand the functions of the following structures: • liver • stomach • esophagus • small & large intestine • esophagus • pancreas • gall bladder • mesenteries • rectum The liver is very large and dark. It has several lobes. You’ll need to lift it out of the way to see the organs beneath. The gall bladder is a small organ attached to the liver. The stomach is may be hidden beneath the liver. Note the esophagus leading into the stomach and the duodenum leading out. The duodenum is the first part of the small intestine. After passing through the large intestine, digested food goes to the rectum before being eliminated from the body. Note that the intestinal tract is attached to the wall of the coelom by mesenteries, which are thin sheets of connective tissue containing blood vessels. stomachliverpancreaslargeintestinesmallintestinediaphragmAbdominal CavityBrian McCauley 12/12/07 Page 5 of 5 The pancreas is white and looks a little bit like cauliflower. It secretes digestive enzymes and buffers. Abdominal cavity: other organs Locate and understand the functions of the following structures: • kidneys • spleen • urinary bladder • urethra • males: testes • females: ovaries, uterus. The spleen is a flat organ located near the stomach. It produces new blood cells and destroys old ones. The kidneys are attached to the dorsal wall of the abdominal cavity (just as they are in a fish). Urine from the kidneys goes into the urinary bladder, and then through the urethra as it