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Name_______________________________________ Section____________ Lab 9: External Anatomy OBJECTIVES 1. To Understand anatomical terms, references and definitions. 2. To Identify important external structures of the fetal pig. 3. Review “organs to know.” MATERIALS NEEDED Double- injected fetal pigs Dissecting materials Gloves PREPARATION Read Biology a Guide to the Natural World Chapter 25 INTRODUCTION Animalia is the kingdom that we are most familiar with and includes organisms such as humans, dogs, whales, and reptiles (plus much more). In this exercise, you will study the anatomy of a fetal pig, which is similar to human’s organs and systems. Mammals are vertebrates having hair on their body and mammary glands to feed their young. The majority are placental mammals in which the developing fetus grows inside the female’s uterus while attached to a membrane called the placenta. The placenta is the source of food and oxygen for the fetus, and also serves to get rid of fetal wastes. CAUTION: When conducting dissections, laboratory safety VERY IMPORTANT. Because scalpels will be used, please do not wear any type of sandal. This will prevent a cut if any sharp object is dropped. Please use gloves at all times if you handle the pig. If any cut or injury occurs, please let your lab Instructor know immediately. HELPFUL WEB SITE This site has the planes of the body. It is a slide show that shows the planes and then it has the anatomical terms and definitions associated with planes on the last slide. It also has study guides of the major systems and quizzes. http://www.whitman.edu/offices_departments/biology/vpd/main.html 64 ACTIVITY I. Anatomical References Cranial region – Refers to the head Pelvic region – Refers to the area around the pelvis Caudal region – Refers to the tail or tail-like structures Ventral - Refers to the belly Dorsal – Refers to the back Medial – Refers to the position near the middle or midline Lateral – Refers to the side of the body Proximal - Nearest to the center, to the midline, or to the point of attachment. Distal – Furthest from the center, from the midline or from the point of attachment 65 Note: In human anatomy, the terms anterior and posterior are used instead of ventral and dorsal, and the terms superior and inferior are used to replace cranial and caudal ACTIVITY: II. External features 1. Obtain a fetal pig and lay the pig on its side in the dissecting pan and locate dorsal, ventral, & lateral surfaces. Also locate the anterior and posterior ends. 2. Examine the pig’s head. Locate the eyelids and the external ears or pinnae. Find the external nostrils. 3. Locate the umbilical cord. With scissors, cut across the cord about 1 cm from the body. Examine the 3 openings in the umbilical cord. The largest is the umbilical vein, which carries 66 blood from the placenta to the fetus. The two smaller openings are the umbilical arteries which carry blood from the fetus to the placenta. 4. Lift the pig's tail to find the anus. Study the ventral surface of the pig and note the tiny bumps called mammary papillary. These are present in both sexes. In the female these structures connect to the mammary glands. ACTIVITY III. Sexing your pig Determine the sex of your pig by locating the urogenital opening through which liquid wastes and reproductive cells pass. In the male, the opening is on the ventral surface of the pig just posterior to the umbilical cord. In the female, the opening is ventral to the anus. Record the sex of your pig. ________________________________________ 67 GLOSSARY Anus - an opening located ventral to the tail where feces is excreted Caudal region – refers to the tail or tail-like structures Cranial region –refers to the head Distal – furthest from the center, from the midline or from the point of attachment Dorsal –refers to the back Genital papilla - a projection of tissue dorsal to the urogenital opening Lateral – refers to the side of the body Mammary papillae: nipples; indicate how many mammary glands there are Medial – refers to the position near the middle or midline Pelvic region – refers to the area around the pelvis Proximal - nearest to the center, to the midline, or to the point of attachment. Scrotum - contains the testes Umbilical arteries - carries oxygen-rich blood to the fetus from the placenta Umbilical cord - connects the fetus to the mother at the placenta Umbilical veins - carries deoxygenated blood from the fetus to the placenta Urogenital opening (female) - opening to the urogenital sinus Urogenital opening (male) - opening to the urogenital sinus Ventral - Pertaining to the belly 68