Chapter 18: Digestion - exam 3

17. Why does the stomach have to be at such a low pH (3 reasons)

-Low pH alters the tertiary structure of protein thereby unfolding them so enzymes can digest them. -Activation of pepsin via pepsinogen -Increase enzyme activity pepsin (lab)

large intestine

Anatomy of the Large intestine: Three sections- 1. Ascending 2. Transverse 3. Descending Major functions- Absorption of water, electrolytes and some vitamins. Special structures- Cecum Appendix Sigmoid colon Anal canal Intestinal microbes

20. Describe the cause, treatments and mechanism for GERD, peptic ulcers and Gastritis.

GERD: Cause: LES Treatments: Prilosec & Prevacid Mechanism: Proton pump inhibitor PEPTIC ULCERS: Cause: H. pylori or NSAIDs Treatments: Prilosec & Prevacid antibiotics Mechanism: Proton pump inhibitor GASTRITIS: Cause: Breakdown of the mucus leads to underlying damage Treatment: Inflammation = histamines Mechanism: Zantac = histamine receptor blocker

5. Name the 6 functions of the digestive system

Motility: movement of food through the tract Secretion: a.-Exocrine: digestive enzymes, hydrochloric acid, mucus, water, and bicarbonate b.-Endocrine: hormones to regulate digestion Digestion: breaking food down into smaller units, both physically and chemically Absorption: passing broken-down food into blood or lymph Storage and elimination: temporary storage and subsequent elimination of undigested food molecules Immune barrier: physical barrier via tight junctions in cells and specialized immune fighting cells.

6. Name the four layers of muscles in the GI tract beginning with the outermost layers.

Serosa: outer binding and protective layer (simple squamous epithelial cells) Muscularis: smooth muscle; responsible for peristalsis and segmentation; myenteric plexus for control by the ANS Submucosa: very vascular, to pick up nutrients; also has some glands and nerve plexuses Mucosa: inner secretory and absorptive layer; may be folded to increase surface area (column epithelial cells)

18. What is pepsin? What cell type secretes it? What is the inactive form? Why do we have an inactive form? What is the substrate for pepsin?

What is pepsin? -Pepsin is a protease that begins digestion of proteins, breaking them into peptides and amino acids. What cell type secretes it? -gastric chief cell What is the inactive form? -pepsinogen, which changes into pepsin when it contacts the acid environment in your stomach. Why do we have an inactive form? -Secreted in an inactive form called pepsinogen (so it doesn't digest protein in the cell producing it!) which is converted to pepsin in presence of HCl and other pepsin molecules already present in lumen. What is the substrate for pepsin? -Pepsin (substrate): protein -Pepsin (end product): large polypeptides

11. What is the swallowing center?

the mouth

34. What are VLDLs, LDLs, HDLs? What is good cholesterol and bad cholesterol?

very-low-density lipoproteins (VLDLs) to deliver triglycerides to organs. low- density lipoproteins (LDLs), which transport cholesterol to organs (no longer contain TAG). *BAD* high-density lipids (HDL) return excess cholesterol to the liver. *GOOD* :) - HDL particles bind to receptors in the blood vessel walls and capture phospholipids and free cholesterol, reducing cholesterol amounts. - Once the HDL is full, it travels to the liver and unloads the cholesterol.

35. Describe the functions of the liver.

*Carbohydrate metabolism: -conversion of blood glucose to glycogen and fat. -production of glucose from liver glycogen and from other molecules (amino acids, lactic acid) by gluconeogenesis. -secretion of glucose into the blood. *Lipid metabolism: -synthesis of TAGS and cholesterol. -excretion of cholesterol in bile. -production of ketone bodies from fatty acids. *Secretion of bile: - Snythesis of bile salts - Conjugation and excretion of bile pigment (bilirubin)

13. What is the function of the stomach? Describe the anatomy of the stomach: gastric pits, gastric gland cells and rugae

*Functions* -Store food -Initiate digestion of protein -Kill bacteria -Move food into the small intestine as a pasty substance: aka Chyme anatomy of the stomach: gastric pits: 'valley'. Gastric pits are indentations in the stomach which denote entrances to the tubular shaped gastric glands. gastric gland cells: Mucus neck cells, Parietal cells, Chief (zygomatic) cells, Enterochromaffin-like (ECL) cells, G cells, D cells rugae: the ridges are called rugae. when the stomach is empty, the rugae more noticeable (the stomach resembles a muscular tube with constricted lumen). when the stomach is full, the rugae flatten out until they almost disappear.

8. What three components are found in saliva?

*Saliva is secreted by the salivary glands -Salivary amylase (Lab and pH) -Microbial agents -Mucus

19. Why does pepsin and the HCL not destroy the stomach?

-Adherent layer of mucus -Tight junctions -Increased mitosis

7. Trace the movement of food from the mouth to the anus naming the organs and sphincters it passes through in order.

-ingestion, mouth, pharynx, salivary glands, epiglottis, trachea, esophagus, esophageal sphincters, diaphragm, stomach, pyloric sphincter, liver, gallbladder, bile duct, appendix, small intestine, lleocecal valve (sphincter) pancreas, pancreatic duct, large intestine, rectum, anus ingestion -Mouth- chews and mixed food with saliva -Pharynx- Directs food from mouth to esophagus -Salivary glands- secrete saliva -Epiglottis - Protects airways during swallowing -Trachea- Allows air to pass to and from lungs -Esophagus- Passes food from the mouth to the stomach -Esophageal sphincters- Allow the passage from mouth to esophagus and from esophagus to stomach, prevent back flow from stomach to esophagus and from esophagus to mouth -Diaphram- Separates the abdomen from the thoracic activity -Stomach- churns, mixes, and grinds food to a liquid mass; adds acid, enzymes, and fluid pyloric sphincter: Allows passage from stomach to small intestine; prevents back flow from small intestine -Liver- Manufactures bile salts, detergent-like substances, to help digest fats -Gallbladder- Stores bile until needed -Bile Duct- Conducts bile from the gallbladder to the small intestine -Appendix- House bacteria and lymph cells -Small intestine- Secretes enzymes that digest all energy- yielding nutrients to smaller nutrient particles; cells of wall absorb nutrients into blood and lymph -llececal valve (sphincter) - Allows passage from small to large intestine; prevents back flow from large intestine -Pancreas- manufactures enzymes to digest all energy- yielding nutrients and releases bicarbonate to neutralize acid chyme that enters the small intestine -Pancreatic duct- Conducts pancreatic juice from the pancreas to the small intestine -Large intestine- Absorbs water and minerals; passes waste along with water to rectum -Rectum - Stores wate prior to elimination -anus- holds rectum closed; opens to allow elimination

13. Cell Exocrine function for each of the following....... 1. Mucus neck cells 2. Parietal cells 3. Chief cells 4. Enterochromaffin cells 5. G cells 6. D cells

1. Mucus neck cells secrete mucus to help protect stomach lining from acid. 2. Parietal cells secrete HCl acid and intrinsic factor (helps small intestine absorb vitamin B12). (HCl - kills bacteria, denatures protein) 3. Chief (zygomatic) cells secrete pepsinogen, the inactive form of a protein digesting enzyme 4. Enterochromaffin-like (ECL) cells secrete histamine and serotonin (paracrine signals). 5. G cells secrete gastrin (hormone). 6. D cells secrete somatostatin (hormone). Also secretes the hormone ghrelin that signals the brain to regulate hunger

32. List the steps for the absorption of fats from the lumen of the small intestine into the epithelial cell of the small intestines then into the blood stream. (note: the role of the liver and gallbladder, micelles, bile, lipase, assembly and disassembly of the fat, chylomicrons)

1. fatty acids and monoglycerides from the micelles within the small intestines are absorbed by epithelial cells and converted intracellularly into triglycerides. 2. These are then combined with proteins to form chylomicrons, which enter the lymphatic vessels (lacteals) of the villi. 3. These lymphatic vessels transport the chylomicrons to the thoracic duct, which empties them into the venous blood (of the left subclavian vein) *Transport of Lipids in Blood: ApoE

33. What is apolipoprotein E? What role does it play in the blood?

Apolipoprotein E is a class of proteins involved in the metabolism of fats in the body Apolipoprotein E (ApoE) plays a major role in the metabolism of dietary fat. It is an important regulator of blood levels of both cholesterol and triglycerides. and plays an integral part in the transport of these fats in the body.

1. What are the three major macromoleules that are digested and absorbed by the GI tract.

Carbohydrates: Large sugars, polysaccharides, that are composed of sucrose, lactose, and maltose as well as glucose, fructose, and galactose. Protein: Large molecules made of multiple amino acids. Nitrogen containing compounds Fats: Lipids (Triacylglycerides) that contain a glycerol backbone and 3 fatty acids.

27. What are found in the pancreatic juices?

Contains bicarbonate and digestive enzymes (20) * but just know 3 below... Amylase: Digests carbohydrate Trypsin: Digest proteins Lipase: Digest lipids

29. What are zymogens? Give an example of one in the stomach and in the pancreas.

Digestive enzymes are released in inactive forms called zymogens. This is necessary to prevent the digestive enzymes from digesting the cells that produce them. In a zymogen, part of the protein blocks the active site of the enzyme. Cleaving off this peptide activates the enzyme. *Most are inactive (zymogenes) until they reach the small intestine. pancreas: Enterokinase activates trypsinogen --> trypsin (to digest protein) stomach: Pepsinogen to form active pepsin

25. What is the role of the enterokinase enzyme that is attached to the brush border?

Enterokinase- activates trypsin (and indirectly other pancreatic juice enzymes); deficiency results in protein malnutrition

4. What are the two divisions of the digestive system?

Gastrointestinal tract (GI tract): Oral cavity, pharynx*, esophagus*, stomach*, small intestine, large intestine ** = Sphincters (circular muscles)* Accessory digestive tract: Teeth, tongue, salivary glands, liver, gall bladder, pancreas

23. What is the structure and function of the "brush border?"

Microvilli -Increase the surface area for absorption -Location of digestive enzymes -Not released into lumen, but stay attached to plasma membrane with active site exposed to chyme -Hydrolyze disaccharides, polypeptides and other substrates to simple nutrient molecules

28. Fill out the info *regarding pancreas enzymes* Enzymes... -Pancreatic Amylase -Trypsin -Lipase -Chymotrypsin give the substrate for each give the site of action for each

Pancreatic Amylase: Secreted by: Pancreas Substrate- Oligosaccharides SOA- Duodenum (small intestine) aka lumen Trypsin: Secreted By: Pancreas Substrate- Polypeptides SOA- Duodenum (small intestine) Lipase: Secreted by: Duodenum brush border enzymes Substrate- Lipid SOA- Duodenum (small intestine) Chymotrypsin: Substrate- SOA-

9. What is salivary amylase? What is its substrate?

Salivary amylase + Starch = Maltose Amylase: Digests carbohydrate -An amylase is an enzyme that catalyses the hydrolysis of starch into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion.

24. Fill in the chart regarding the enzymes *found on the brush border*: Enzymes... -Sucrase -Maltase -Lactase -Aminopeptidase give the substrate for each give the site of action for each

Sucrase: Substrate- Sucrose SOA-Duodenum (small intestine) Maltase: Secreted by: Brush Border Enzymes in the Duodenum Substrate- Maltose SOA- Duodenum (small intestine) Lactase: Substrate- Lactose SOA-Duodenum (small intestine) Aminopeptidase: Substrate- SOA-Duodenum (small intestine)

10. Why is chewing important?

The physical process of chewing food in your mouth helps to break down larger particles of food into smaller particles. This helps to reduce stress on the esophagus and helps the stomach metabolize your food. When you chew each mouthful properly, you also release a lot of saliva, which contains digestive enzymes.

anatomy of the small intestine

Three sections: 1. Duodenum 2. Jejunum 3. Ileum Major functions: -Digestion -Absorption Special structures: -Villus: fingerlike projection -Intestinal crypts -Microvillli

22. What are Villus, intestinal crypts? What two cell types are found in the intestinal crypts? What are their functions? What cell types is found amongst the simple columnar epithelial?

What are Villus, intestinal crypts? What two cell types are found in the intestinal crypts? Intestinal Stem Cells & Paneth cells What are their functions? -ISC- Replenish cells / Secretory and enterocytes -PS- secrete antibacterial / Enzymes (lysozyme and peptides What cell types is found amongst the simple columnar epithelial? -Goblet cells: Mucus secreting cells

3. Fill in the blanks below: Define polysaccharide, disaccharide and monosaccharide ________________ + ________________ = sucrose ________________ + ________________ = lactose ________________ + ________________ = maltose

__glucose___ + ___fructose___ = sucrose __glucose__ + __galactose__ = lactose __glucose__ + __glucose__ = maltose

26. a. Name the function of the pancreas? b. Differentiate between endocrine and exocrine function. c. What are the products of exocrine function? d. What are the productions of endocrine function?

a. The pancreas is an organ located in the abdomen. It plays an essential role in converting the food we eat into fuel for the body's cells. The primary digestive function of the pancreas is production and release of pancreatic juice. The function of pancreatic juice is digestion and absorption of food. b. The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar. *Exocrine - digestive *Endocrine - hormonal c. The exocrine glands produce enzymes important in digestion. These enzymes include trypsin and chymotrypsin to digest proteins; amylase for the digestion of carbohydrates; and lipase to break down fats. d. The endocrine component of the pancreas consists of islet cells (islets of Langerhans) that create and release important hormones directly into the bloodstream. Two of the main pancreatic hormones are insulin, which acts to lower blood sugar, and glucagon, which acts to raise blood sugar.

16. What is the role of gastrin and histamine in regulating parietal cells.

histamine: activates parietal cells to release HCL gastrin: Increases HCL secretion

15. Pariteal cells can be regulated by (3):

it's controlled by Paracrine, Endocrine, and Neuronal mechanisms *These cells are located in the gastric glands found in the lining of the fundus and in the body of the stomach.

2. Draw the structures for #1.

next 3

31. List the steps for the absorption of amino acids from the lumen of the small intestine into the epithelial cell of the small intestines then into the blood stream.-- figure 18.33 pg.652

pg. 652 1. polypeptide chains of proteins are digested into free amino acids, peptides, and tripeptides by the actions of pancreatic juice enzymes & BB enzymes. 2. The amino acids, dipeptides, tripeptides all enter the duodenal epithelial cells. 3. Dipeptides and Tripeptides are hydrolyzed into free amino acids within the epithelial cells, and these products are secreted into intestinal fluid and then into capillaries which eventually drain into the hepatic portal vein.

12. Define peristalsis.

the involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wavelike movements that push the contents of the canal forward.

37. What are the three phases of gastric secretions?

three phases of gastric secretion are called the cephalic, gastric, and intestinal phases. Cephalic Phase- Controlled by brain: sight, smell, taste of food relays nerve impulses to brainstem to signal stomach to secrete gastric juice and gastrin Gastric Phase- Begins when food enters stomach: stretching of stomach increases secretion of gastric juice and gastrin Intestinal Phase- When chyme moves into the duodenum: duodenum triggers nerve impulses and hormones to inhibit gastric secretion