DIGESTIVE SYSTEM STUDY GUIDE

33. What are the parts of intestinal villi?

- intestinal glands - vascular capillary beds - lacteals - smooth muscle to squeeze lacteal and move villi to expose membrane to nutrients within intestinal border - brush border:

2. What are the accessory organs of the digestive system?

- salivary glands - liver - gallbladder - pancreas

45. Know each of the hormones and enzymes that are important in the digestive system process:

Enzymes and hormones charts

19. What are the components of gastric juice? What do these enzymes digest?

These digestive enzymes are pepsin and rennin, hydrochloric acid, and mucus + intrinsic factor. Pepsin breaks proteins down for further chemical digestion in the small intestine; it is aided in this by hydrochloric acid, which provides the acid environment in which pepsin is most effective.

34. What do villi, lacteals, and intestinal capillaries absorb? * answer needs work

They absorb nutrients, lipids, broken down proteins and carbohydrates

31. What is a lacteal?

a lymphatic capillary that transports lipids* and materials that cannot enter blood capillaries *because lipid droplets would float in the plasma made up for 90% water.

40. What is the appendix?

an accessory structure containing intestinal flora and many lymphoid nodules, and connects to cecum region of the large intestine.

43. What is the effect of taking an antacid and how would it affect digestion?

an antacid alkalinizes the gastric contents, which would disrupt pepsin and other gastric enzymes and acids to function properly. A lower pH in the stomach also impairs gastric juice ability to destroy pathogens and makes the stomach susceptible for H. pylori infections.

what is the primary way the body controls pH?

bicarbonate pathway CO2 + H20 -> H2CO3 -> HCO3- + H+ - mediated by carbonic anyhydrase to create bicarbonate ions and hydrogen ions from CO2 and water.

16. What are the three stages of gastric secretion and what are the major events in each?

cephalic- begins w/ sensations or thoughts of food. CNS prepares for arrival of food: Parasympathetic impulse down vagus nerve tells stomach to increase gastric juice secretion gastric phase- begins with signals when food arrives in the stomach: presence of undigested materials, stomach distention, increase in pH of the gastric content due to food temporarily neutralizing it, so more gastric juice is needed. **major event: gastrin secretion increases mixing of stomach and secretions by parietal and chief cells intestinal phase- The intestinal phase occurs in the duodenum as a response to the arriving chyme, and it moderates gastric activity via hormones and nervous reflexes. **major event: initiation of the gastric reflex - to inhibit gastrin production, decreasing gastric mixing and secretions stimulates contraction of pyloric reflexes, easing chyme release into duodenum. increases mucus production in duodenum.

29. What are the 3 segments of the small intestine?

duodenum, jejunum, and ileum

28. What are the functions of bile salts?

emulsification of large lipid droplets into smaller blobs to be broken down by lipase.

10. What is the structure that stops the movement of food back into the esophagus?

esophageal sphincter

41. The ability to digest a particular compound may be caused _____________.

having the proper enzymes to breakdown the particular compounds

36. What is the primary function of the large intestine?

main job is to absorb water and produce feces (undigestible material), also does absorption of few vitamins thanks to bacterial enzymes

1. What are the four layers of the digestive tube?

mucosa, submucosa, muscularis externa, serosa

9. What is the primary secretion produced by the esophagus and does it take part in the digestion?

mucous secretion secreted by esophageal glands: reduces friction between bolus and esophageal lining.

38. What gives feces its color?

stercobilins- a pigment compound secreted with bile, is the end product of heme breakdown by the liver, responsible for making excrement brown

27. What is the function of the gallbladder?

to store and concentrate bile

25. Name the major functions of the liver

- produce bile - recycle RBC - detoxification - produces glycogen <---> glucose, - glucogenesis - oxidizes fatty acids - synthesizes lipoproteins, phospholipids, and cholesterol - converts carbohydrates and proteins into fats - deamination of amino acids - forms urea - synthesizes plasma proteins and clotting factors - converts some amino acids to other amino acids - stores glycogen, iron, and vitamins A, D, and B12

3. What are the two movements of the digestive tract?

-peristalsis: waves of muscular contractions -segmentation: cycles of contractions

11. Name the four regions of the stomach

1. Fundus: superior to esophageal connection 2. cardia: within 3 cm of gastroesophageal junction, secretes mucus to protect esophagus. 3. body: largest region 4. pylorus: sharp curve of J

37. What is the composition of feces?

75% water 5% bacteria 20% indigestible material, inorganic matter, and epithelial cells

17. What is a bolus...what is chyme?

A bolus is a small rounded mass of a substance, especially of chewed food at the moment of swallowing. In peristalsis, a bolus is moved along the length of the digestive tract. In the stomach, chyme is food, saliva, and gastric gland secretions.

39. Why are bacteria important in the large intestine?

Bacteria in the large intestine are important for the absorption of: biotin, vitamin K, and B5

15. Why is intrinsic factor important?

Binds to vitamin B12 & aids in its absorption in the small intestine, and failure to produce or utilize intrinsic factor results in the condition pernicious anemia. *Function of the stomach (source: gastric glands)

4. Describe the functions of the mouth and its parts:

Functions: 1. sensory analysis of materials before swallowing 2. mechanical processing through actions of teeth, tongue, and palatal surfaces 3. lubrication: mixing with mucus and salivary gland secretions 4. limited digestion of carbs and lipids Parts: - Oral mucosa: lining of the oral cavity - labia: the mucosa of each cheek is continuous with that of the lips. - vestibule: space between the cheeks and the teeth

13. Why is hydrochloric acid important important in gastric juice?

Gastric juice is a unique combination of hydrochloric acid (HCl), lipase, and pepsin. HCl functions: 1. destroy pathogens 2. denature proteins 3. activate pepsinogen 4. denature salivary amylase. > H+ from the bicarbonate pathway and Cl- are released to control pH Its main function is to inactivate swallowed microorganisms, thereby inhibiting infectious agents from reaching the intestine.

24. What do hepatic cells produce?

Hepatic cells produce bile

12. What are the specialized cells found in the gastric mucosa and what are the secretions that they produce?

Mucous cells: secrete an alkaline mucus that protects the epithelium against shear stress and acid Parietal cells: secrete intrinsic factor and HCl precursors Chief cells: secrete pepsinogen, once in acid becomes active pepsin (proteolytic enzyme) - in infants, chief cells secrete rennin and gastric lipase for milk digestion G cells/enteroendocrine cells: secrete the hormone gastrin, and a variety of hormones to regulate stages of digestion along the tract.

44. if you lacked the enzyme sucrase, what effect would this have on your dietary intake of calories? Why is nutrasweet calorie free?

Not having sucrase would mean not being able to break down sucrose, which leads to not getting any calories from consuming added sugar. artificial sweeteners rely on humans missing the specific enzyme to break down those molecules and get any energy from them.

20. Why is it important to secrete some enzymes in inactive forms?

Protein digesting enzymes are secreted in an inactive form to protect the organs and glands from digestion by the enzymes. If they are released in the active form, they start digesting the glands carrying them and the site where they are released.

7. What is the primary enzyme found in the saliva and what reaction does it catalyze?

Salivary amylase, catalyzes breakdown of starches into maltose disaccharides

14. How does the hydrochloric acid effect the activity of salivary amylase?

The HCl in the stomach lowes pH, denaturing salivary amylase and other proteins by breaking down the structure and, thus, the function of it.

How does pancreatic juice inactivate gastric juice?

The alkaline pH of pancreatic juice (pH 7.5-8.0) serves two important physiological purposes. First, it dissolves and activates the pancreatic digestive enzymes secreted by the acinar cells. Second, it neutralizes HCl being emptied into the duodenum by the stomach.

8. Describe the structure and function of the esophagus.

The esophagus is an hollow muscular tube about 10 inches long and <1inch wide, has longitudonal folds, and non-keratinized mucosa epithelium. *esophageal glands in submucosa produce mucus to reduce friction between bolus and esophageal lining. Function: - to transport food down from the oral cavity to the stomach

23. What is the structure of the liver?

The liver is the largest organ, has 4 lobes, and is composed of liver lobules, or hexagons of hepatocytes formed in plates radiating from the center of the lobule, separated by interlobular septa. A triad of branches of portal vein, hepatic artery, and bile duct at each corner. -innervated by sinusoid capillaries (large gaps so damaged RBCs can enter the liver for recycling) which drain into central vein of each hexagon lobule. macrophages Kupffer cells within the tissue.

18. Describe the location and structure of the pancreas?

The pancreas stretches from behind the stomach to the left upper abdomen near the spleen. It is divided into a head, neck, body, and tail. Made of exocrine pancreatic acinar cells, and pancreatic islets

30. How does the small intestine mucosa enhance absorption?

The small intestine mucosa has the following structures that add 600x more surface area to increase absorption: -plicae circularis: transverse folds -intestinal villi: projections of mucosa -microvilli: brush border, also has enzymes for digesting nutrients.

26. What are the components of bile?

bile salts

35. Name the parts of the large intestine:

cecum: ileocecal valve, appendix attached colon: ascending, transverse, descending, sigmoid, -taeniae coli: 3 muscle bands along outer colon surface -haustra: pouches along colon -fatty appendices: teardrop-shaped fat sacs along colon attached to serosa rectum

6. Describe the following structures associated with the tooth: enamel, dentin, cementin, pulp cavity, periodontal ligament.

enamel: a layer of tough substance coating the tooth. dentin: a mineralized matrix similar to that of bone, acellular, the bulk of the tooth. cementin: a layer covering the dentin of the root, providing protection and anchoring periodontal ligament. pulp cavity: receives blood vessels and nerves through the root canal(a space where vessels go down) periodontal ligament: a ligament that binds the tooth to the socket

32. What are the secretions of the small intestine and what are their functions?

enzyme secretions by small intestine: maltase: breaks down maltose into 2 glucose - sucrase: breaks sucrose into glucose & fructose - lactase: breaks lactose into glucose and galactose - peptidases: break peptide bonds between amino acids in proteins - enterokinase/enteropeptidase: convert trypsinogen into trypsin hormone secretions by duodenum: - gastrin: increases stomach mobility and production of gastric acids and enzymes. - secretin: increases secretion of bile from liver and buffers from pancreas, decreases gastric motility and secretory rates - GIP/gastric inhibitory peptide: inhibits gastric activity while increasing insulin release, also stimulates duodenal glands, lipid synthesis in adipose, increased skeletal muscle glucose use - CCK/Cholecystokinin: increases release of bile, and enzyme production from pancreas, also reduces gastric activity and hunger sensation - VIP/vasoactive intestinal peptide: stimulates secretion of intestinal glands, dilates regional capillaries, and inhibits gastric acid production - enterocrinin: stimulates mucin production

5. Explain the different shapes of the teeth and what functions are they specialized to do:

incisors- clipping or cutting cuspids- tearing or slashing bicuspids- crush, mash, and grind molars- deciduous- primary milk teeth, baby teeth

42. If a person has 95% of the stomach removed, how would the digestion and absorption of foods be affected?

the stomach plays a major role in proteolysis, so digestion of proteins would be slower and more taxing. the stomach also produces intrinsic factor, so the ability to absorb vitamin B12 in the small intestine would be severely impaired and the patient may need to have B12 shots to help this process and to prevent pernicious anemia.

21. What is the function of mucus in the digestive system?

Mucus is used as a lubricant for materials that must pass over membranes, e.g., food passing down the esophagus. *Mucus is extremely important in the gastrointestinal tract. Protects the epithelial lining of the digestive tract from abrasion and erosion and protects the stomach epithelial lining from acids, gastric juice, and enzymes.