1. 1 The Digestive System Lab 11 rev 4-11 Digestion is a process of breaking down large molecules contained in food into basic building blocks which our body can then use as nutrients. Digestion process accomplished in 2 ways: –mechanical digestion--breaking down of large food particles into smaller pieces BIOL 102-Digestive System

2. 2 The Digestive System Lab 11 chemical digestion--takes these smaller pieces, extracts the proteins, starches, or fats and then processes these into their building blocks: amino acids, sugars, fatty acids and glycerol. –Enzymes and other chemicals help with chemical digestion –see table 15.1 on page 142 of the manual for a list of major digestive enzymes and chemical reactions the digestive system also stores the waste by- products from the digestive process until it can be eliminated from the body. BIOL 102-Digestive System

3. 3 The Digestive System - Lab 11 The digestive system includes: –mouth --small intestine –pharynx --large intestine –esophagus --rectum –stomach --anus These organs are collectively called the Gastrointestinal System or Tract. It is actually a hollow tube extending from the mouth to the anus. –The space within the tube is called the lumen. Structure of the walls of the digestive tract –consists of 4 layers of tissue –serosa, the outer layer; is made up of connective tissue covered with an epithelial membrane. BIOL 102-Digestive System

4. 4 The Digestive System Lab 11 –muscularis-the thickest part of the wall; is composed of 2 layers of smooth muscle. Each layer runs in a different direction this layer is responsible for peristalsis (the wavelike propulsion of material through the digestive tract) and segmentation (the back and forth mixing of food which occurs primarily in the small intestine). BIOL 102-Digestive System

5. 5 The Digestive System Lab 11 –submucosa-made of connective tissue which contains blood, lymphatic vessels, and nerves. This layer also has a lot of elastic fibers. This enable the stomach to stretch with meals and regain its usual shape after meals. Lymphatic capillaries in the digestive tract are called lacteals. They play a major role in absorbing digested fat from the intestine. –mucosa-the innermost layer which is composed of simple columnar epithelium BIOL 102-Digestive System

6. 6 The Digestive System Lab 11 The mouth (or oral cavity) –mechanical and chemical digestion occur here the teeth and tongue break food into smaller pieces (mechanical digestion) the salivary glands secrete water, mucus and an enzyme, amylase, to begin the process of chemically digestion The pharynx (throat) is where swallowing starts. The esophagus is a muscular tube. As we swallow, we push food along in this tube until the food reaches our stomach. BIOL 102-Digestive System

7. 7 The Digestive System Lab 11 The stomach performs both chemical and mechanical digestion. –Mechanical is the crushing and churning of food performed by the smooth muscle in the wall of the stomach –Chemically, the stomach produces pepsin and hydrochloric acid (HCl) which continue to break down food –Food is liquefied here before continuing further down the intestinal tract BIOL 102-Digestive System

8. 8 The Digestive System Lab 11 The small intestine is the major site of chemical digestion –finishes the job of breaking down food –named small intestine because of the diameter of the tube –is divided into sections to help identify how different areas of the small intestine function the first section is the duodenum (approximately 10 inches long) the second section is the jejunum (10 ft long) the last section is the ileum (10 ft long) BIOL 102-Digestive System

9. 9 The Digestive System Lab 11 The structure of the wall of the small intestine helps in absorption –the mucosa (name of the tissue of the walls) contains many large folds covered with small fingerlike projections called villi –each epithelial cell of the villi contain microvilli which are smaller fingerlike projections –the villi and the microvilli enlarge the surface area of the small intestine thus increasing its ability to absorb nutrients BIOL 102-Digestive System

10. 10 The Digestive System Lab 11 The duodenum (first section or region) –most digestion actually occurs here –the pancreas contributes enzymes and sodium bicarbonate (NaHCO 3 ) into the duodenum to help with digestion –the liver and gallbladder deliver bile bile is a surfactant which breaks large fat globules into smaller globules; this is actually a mechanical (vs. chemical) change the jejunum and the ileum are where most nutrient and water absorption occurs BIOL 102-Digestive System

11. 11 The Digestive System Lab 11 The large intestine –mainly involved in water absorption, solidification and storage of digestive wastes –named large intestine because of its diameter (approximately 2-1/2 inches vs. 1 inch) –has several sections: –Cecum (a blind pouch) –colon (this is further broken down into the ascending, transverse, descending and sigmoid colon) –rectum –anus BIOL 102-Digestive System

12. 12 The Digestive System Lab 11 The large intestine begins at the cecum. A small fingerlike pouch, called the appendix, extends out of the cecum. It has no known digestive function. The colon begins at the end of the cecum. –The position in the abdomen of the ascending, transverse, and descending colon are reflected by the names of each of these sections. –The sigmoid colon joins the end of the descending colon and ends in the rectum. BIOL 102-Digestive System

13. 13 The Digestive System Lab 11 –The anal canal is the name of the passageway from the rectum to the anus through which the fecal matter or feces (the technical name of the solid waste material) passes in order to exit the body. Microorganisms that live in the large intestine produce vitamin K which is important for blood clotting. BIOL 102-Digestive System

14. 14 The Digestive System Lab 11 Metabolism –a calorie is a measure of heat energy as well as a way to quantify the amount of energy stored in food. –Nutritionists are actually using the term kilocalorie when they describe calories. So, when you see the term “Calorie” used with a capital “C”, the lab manual is referring to kilocalories. –The Peanut Test activity on page 147 demonstrates the connection between calories and heat energy and demonstrates how much more efficient the human body is at extracting energy from food than fire is. BIOL 102-Digestive System

15. 15 The Digestive System REMINDER, page 1: 1. Learn the digestive system structures on the models. Use the figure on page 143 as a guide. You don't need to know the specific names of each of the salivary glands. 2. Use the model of the digestive tract wall to learn the four tissue layers and key structures (serosa, muscularis, submucosa, mucosa, villi, capillary and lacteals). BIOL 102-Digestive System

16. 16 The Digestive System REMINDER, page 2: 3. On the fetal pig, learn the bulleted, bold print structures on pages 145-146. –The pig figures in the lab book are hard to follow, so use the color photos on your tables to make this easier. –Also note that a pig doesn't have an ascending or transverse colon. 4. Do the Peanut Test activity on page 147 and the Enzyme Function activity on pages 148-9. Use 1 peanut without the shell and the large test tubes. –DON'T EAT THE PEANUTS; they are very old (anywhere from 3 months to 3 years). BIOL 102-Digestive System