a. parotid b. sublingual c. submandibular

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Leslie Lyons
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Bozeman Science/ Nature The Digestive System Watch the videos, and answer the questions below. Please write your answers in complete sentences, and explain all concepts thoroughly. 1.

1 Bozeman Science/ Nature The Digestive System Watch the videos, and answer the questions below. Please write your answers in complete sentences, and explain all concepts thoroughly. 1. What are the four categories of dietary macromolecules? a. Carbohydrates b. Proteins c. Lipids d. Nucleic acids 2. What is meant by the term, You are what you eat? Explain how large, bulky molecules are broken down. The food we consume is largely made up of large polymers or macromolecules. Through the process of mechanical and chemical digestion, these very large molecules are broken down into what are called monomers. These monomers are then reorganized in our cells to form protein building blocks for our tissues, and glycogen stores for immediate energy demands, and lipid stores for future energy demands. Carbohydrates are broken down into individual monosaccharides of glucose, fructose, and galactose by the enzyme amylase. Proteins are broken down into smaller peptide chains by peptase, then decomposed further into amino acids by proteases. Lipids (triglycerides) are cleaved into individual fatty acids and glycerol by lipases. Nucleic acids are broken down by nucleases. 3. What are the three salivary glands? Label them on the figure. a. parotid b. sublingual c. submandibular Bozeman Science The Digestive System/ Video Worksheet / Anatomy & Physiology/ PEP 1

What is the function of the various teeth and tongue in digestion? Label the structures in the mouth in the figure below.

2 4. What is the composition and function of saliva? Saliva is 99.5% water and 0.5% dissolved solutes. The dissolved solutes are composed of the enzyme amylase (which digests carbohydrates amylose starch), the enzyme lysozyme (which kills bacteria) and mucous to lubricate food and aid in digestion. 5. What is the function of the various teeth and tongue in digestion? Label the structures in the mouth in the figure below. The incisors in front cut into food, the cuspids tear and shred food, the premolars crush and grind food, and the molars grind food down. The muscular tongue pushes food against the teeth and hard palate to crush and mechanically break it down. 6. How does food not fall into our esophagus in the process of eating, or rise up into the nasal cavity? Contrast the pharyngeal phase of eating with that of the esophageal. Label the structures in the figure below. During the pharyngeal phase of swallowing, the tongue rises against the soft palate, closing the nasopharynx, and the epiglottis seals off the larynx (voice box) so the bolus is directed down the esophagus. During the esophageal phase of swallowing, food moves through the esophagus into the stomach through peristalsis. Bozeman Science The Digestive System/ Video Worksheet / Anatomy & Physiology/ PEP 2

7. Label the structures on the stomach at right. Label both the lower esophageal sphincter and the pyloric sphincter. What is the role of these sphincters?

The pyloric sphincter gradually allows portions of chyme to enter the small intestine. 8. What is the role of the stomach in both mechanical and chemical digestion?

3 7. Label the structures on the stomach at right. Label both the lower esophageal sphincter and the pyloric sphincter. What is the role of these sphincters? The lower esophageal sphincter keeps food and gastric juice from entering back up into the esophagus. When the sphincter is weak, the condition is called gastroesophageal reflux disease (GERD). The pyloric sphincter gradually allows portions of chyme to enter the small intestine. 8. What is the role of the stomach in both mechanical and chemical digestion? The stomach has muscle fibers running in all directions with a longitudinal, circular, and oblique layer. The fibers move in all directions and are able to mechanically grind the food down further. Enzymes and HCl take part in chemical digestion; the combination of food maceration and chemicals in the stomach create a less viscous paste called chyme. 9. What is the role of chief and parietal cells, and their products? Chief cells secrete an inactive enzyme called pepsinogen, and parietal cells in the lining of the stomach produce hydrochloric acid. The hydrochloric acid kills bacteria, denatures proteins, and activates the enzyme pepsinogen into pepsin. The combination of all these substances comprise gastric juice. 10. Since the stomach produces powerful enzymes called proteases, how does it not digest itself? Mucous production. 10. What are the three sections of the small intestine? Label them in the figure at right. What is the role of the duodenum? The small intestine is made up of (1) the duodenum smallest section, (2) the jejunum and (3) the ilium. The entry point of material from the stomach into the small intestine. There are several ducts at the duodenum, a bile duct from the gall bladder, and two from the pancreas. Bozeman Science The Digestive System/ Video Worksheet / Anatomy & Physiology/ PEP 3

11. Where are the bile salts synthesized? What organ stores these? What is their function? The liver produces bile and then bile is stored and concentrated in the gall bladder.

In doing so, large fat droplets are broken down into smaller fat droplets and are more easily digestible. 12. What is the function of the pancreas in digestion?

4 11. Where are the bile salts synthesized? What organ stores these? What is their function? The liver produces bile and then bile is stored and concentrated in the gall bladder. Because dietary fats must be digested in a watery environment, and fats and water simply do not combine chemically, bile salts emulsify fats by binding to both fat molecules and water molecules. In doing so, large fat droplets are broken down into smaller fat droplets and are more easily digestible. 12. What is the function of the pancreas in digestion? The pancreas releases several enzymes, lipase (which digests lipids), amylase (digests amylose), trypsin (digests proteins), chymotrypsin (other proteins) and finally, nucleases (break down RNA, DNA). 13. Using Figure in the text, label all the structures in the figure above right. 14. Label the structures in the image below, using Figure in the text, and then discuss what makes the jejunum histologically perfect for its function. The villi and microvilli present a tremendous amount of surface area for the absorption of nutrients. Note in image there are capillaries that come to the surface of the absorption cells and carry nutrients taken in to the rest of the body. Nutrients (now in the form of monomers) enter into the blood stream by either passive transport (diffusion) or by active transport (requiring ATP). Bozeman Science The Digestive System/ Video Worksheet / Anatomy & Physiology/ PEP 4

5 15. Label the three sections of the large intestine (colon) in the figure below. 16. What is the function of the colon? The colon absorbs water produced by the digestion process, and houses colonies of bacteria that synthesize vitamin K. 17. Is the appendix completely useless? Perhaps not, it is now thought the appendix acts as a storehouse and nursery for good bacteria, rebooting the digestive system after diarrheal illnesses. 18. Where are carbohydrates broken down? In both the mouth (salivary amylase) and in the duodenum (pancreatic amylase) carbohydrates are broken down. 19. Where does protein digestion occur? Protein digestion occurs in the stomach, with the release of pepsin. Protein is further digested in the duodenum where pancreatic trypsin and chymotrypsin are released. 20. In what region of the body are lipids digested, and how are they digested? Lipids are broken down in the duodenum. There, pancreatic lipase starts the cleavage of the molecules, and then bile released from the bile duct into the duodenum works to emulsify the lipids. 21. Where are nucleic acids digested? In the duodenum, where pancreatic nucleases are released. 22. Where do the nutrients go after they are broken down and absorbed by the small intestine? Once digested and taken up by the small intestine, nutrients are carried to the liver by the portal vein, where the liver then sorts the nutrients out, and detoxifies them, if necessary. Bozeman Science The Digestive System/ Video Worksheet / Anatomy & Physiology/ PEP 5

The Human Digestive Tract

The Human Digestive Tract The Mouth salivary glands (parotid, sublingual, submaxillary) - produces saliva --->lubricate food ---> dissolves food particles ---> allows us to taste food --->contains amylase