11 fetal pig I - notes PDF

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Biology 105

Spring 2016

LAB #11 FETAL PIG ANATOMY I EXTERNAL; ORAL CAVITY/PHARYNX; DIGESTIVE SYSTEM (M. Barry modified by N. Holtzman) BEFORE CLASS: Read this lab, know the definitions of any words in bold and write the purpose of today’s lab in your lab notebook. PROBLEMS: ● Our bodies must carry out many important biological processes every day simply to survived. We must respond to our environment and work to keep our bodies functioning within these environments. OBJECTIVES: In the following laboratory exercise, you will examine in some detail the external and internal anatomy of a fetal pig (Sus scrofa). The pig is a mammal. Many aspects of its structural and functional organization are identical with those of other mammals, including humans. Thus, a study of the fetal pig is in a very real sense, a study of humans. By the end of this lab you should: ● Have respect for the fetal pig you are working on. ● Have a basic understanding of the external morphology of the pig. ● Have a basic understanding of the structures and function of both the oral cavity/ pharynx and the digestive system. SUPPLEMENTAL VIDEOS: http://www.execulink.com/~ekimmel/fetal0.htm http://www.youtube.com/watch?v=lWikhoXMxkI http://www.youtube.com/watch?v=tr03Y8CtqkA ETHICS: The fetuses you will use in the following weeks were salvaged from pregnant sows being processed for food. They are not raised specifically for dissection purposes. The fetuses are removed from the sow and embalmed with a preservative, which is injected through the umbilicus. Following this, the arterial and venous systems are injected under pressure with latex, a rubber-like compound. Arteries (red) are injected through the umbilicus; veins (blue) are injected through one of the jugular veins at the base of the throat. With the possible exception of the abdominal cavity, organs rarely appear as they are presented in a diagram. If the purpose of this exercise were simply to have you memorize diagrams (or computer screens), we would do only that and bypass the expense, time, and controversy of dissecting! Dissection is a powerful teaching method, especially for concrete thinkers and visual learners. Only by dissecting can you really appreciate the structural and functional role of the many membranes, mesenteries, and connective tissues that will impede your progress every step of the way. Only by dissecting can you really appreciate the relationship between an organ's texture, location, and function. You are expected to take your dissection seriously and utilize your pig to the fullest extent possible. INTRODUCTION: 1

Biology 105

Spring 2016

You will work in pairs for this lab. You will have to examine others’ dissections to see pigs of a sex other than that of yours. You may use the laboratory manual Anatomy and Dissection of the Fetal Pig by Walker and Homberger for additional insight. Your notebook should contain drawings of histological sections and answers to questions.

LABORATORY ACTIVITIES: Materials Dissection kit Laboratory Handout Dissection tray

String Fetal pig Microscope slides: cross-sections of duodenum, esophagus

Procedure Wear protective gloves. Let the pig soak in the sink for a little while to remove some of the preservative before dissecting it. Do not let the pig dry out. Keep it moist when you pack it away between classes. To get started, READ the students guide at the beginning of the manual, and learn the cardinal planes of section and orientations such as superficial, deep, lateral, medial, rostral, caudal. When dissecting, LESS is MORE. Avoid cutting deeply; scissors are often better than scalpels. Blunt dissection is often all that is needed. Blunt dissection is effectively using a probe to separate and delineate structures by running a blunt probe along the orientation of a structure like a blood vessel. 1. External Anatomy (pp. 1 – 4) Checklist: i. head, neck, trunk, appendages, tail ii. rostral plate, external nostrils iii. mouth, lips iv. auricle v. eyes, eyelids, nictitating membrane vi. thorax, abdomen vii. umbilical cord, arteries, vein viii. preputial orifice, scrotum, anus ix. urogential orifice, genital papilla x. mammary papillae xi. wrist, ankle, elbow, knee xii. vibrissae xiii. mental gland

2. Head and Neck: Salivary glands (pp.38) 2

Biology 105

Spring 2016

Checklist: i. parotid gland ii. masseter 3. Head and Neck: Mouth, Pharynx (pp. 38 – 40) Checklist: i. oral cavity (label in figures below) a) teeth b) tongue ● fungiform papillae ● filiform papillae ● vallate papillae ● taste buds c) hard palate ● rugae ii. nasal cavity (label in figures below) iii. pharynx iv. oral pharynx v. laryngeal pharynx 4. Head and Neck: Mouth, Pharynx (p 41) Note in particular how the epiglottis (that protects the airway) and the slit-like opening of the glottis fit into the entrance to the nasal pharynx. This allows air to pass from the nasal cavity into the larynx and trachea. This arrangement makes it easier for the pig to drink and breath (nasally) efficiently without getting fluid in the airway. During swallowing the tongue pushes down on the epiglottis, and the slits of the glottis and larynx are closed, allowing food to be pushed into the esophagus without entering the airway. The arrangement of the epiglottis in the fetal pig is largely retained in most adult mammals, but in humans, in order to facilitate speaking, the epiglottis and glottis descend. This is critical for speaking, but makes it harder to eat and breathe (or talk) at the same time. There are undesirable consequences if you try.

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Biology 105

Spring 2016

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Biology 105

Spring 2016

5. Body Cavity (pp. 42 – 44) Checklist: i. diaphragm ii. viscera iii. coelom iv. peritoneal cavity v. mesenteries 6. Digestive Organs of the Abdomen: Stomach Checklist: i. liver (identify lobes) ii. stomach iii. esophagus iv. spleen v. pyloric sphincter Note that the pyloric sphincter between the stomach and the duodenum and the cardia sphincter between the stomach and esophagus are muscular valves that keep the highly acid contents of the stomach in the stomach. The pyloric sphincter also regulates flow of partially digested food into the small intestine. 7. Digestive Organs of the Abdomen: Small intestine and digestive glands. Checklist: i. duodenum ii. jejunum and ileum (transition between these subdivisions are not obvious) iii. pancreas, pancreatic duct iv. gall bladder, common bile duct v. villi 8. Digestive Organs of the Abdomen: Large intestine Checklist: i. colon ii. caecum iii. coiled part of colon, transverse colon, descending colon iv. rectum v. anus 9. Microscopic Structure of esophagus Examine the cross section of he esophagus with a compound microscope. There is a lot of muscle here. What is all this muscle for? Note that there are 4 main layers in common to all of the digestive system: i. A thin simple squamous epithelium or serosa surrounding the outside of the esophagus. ii. Two external muscle layers of circular and longitudinal muscle fibers. Since this is a cross section, the longitudinal muscles (superficial) are cut in cross section. The circular muscles (deep) appear to be going around in a circle. iii. A submucosal layer that contains connective tissue, as well as vessels and nerves. 5

Biology 105

Spring 2016

iv.

A mucosal layer includes at its base muscles, connective tissue and a columnar epithelium lining the lumen.

10. Microscopic Structure of Small Intestine: duodenal cross section (pp. 51 – 53) Checklist: i. serosa ii. longitudinal muscle iii. circular muscle iv. submucosa v. mucosa vi. simple columnar epithelium vii. villi LABORATORY ASSESSMENT: Laboratory notebook should contain: 1. A statement of purpose 2. Any observations you might make as you carry out your dissections. 3. Answers to all the questions for each section as you go along the lab. Questions to hand in at the beginning of Lab 12: 1) How do the epithelia between the esophagus and small intestine differ? 2) What are the functional reasons for the different structures? 3) What are the major structures of the digestive tract in order starting with the mouth? 4) What are the large glands associated with the digestive tract and where do the ducts from these glands enter the tract? 6...