Answers, BIO 2320, Digestive

Objectives – 3, BIO 2320, Digestive SystemAnswers


1.Mechanical & physical breakdown of food, followed by its absorption. Alimentary = GI tract = all of the organs listed in #3.

2.Ingestion, movement, digestion, absorption, defecation

3.Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine

4.Salivary glands, teeth, tongue, pancreas, liver, gall bladder

5.Mucosa, submucosa, muscularis, serosa = visceral peritoneum

6.Parietal peritoneum is the shiny lining of the abdominal cavity, visceral peritoneum is the shiny outer surface of the abdominal viscera and the cavity is between the two.

7.Falciform ligament from liver to ventral body wall, Mesentery proper from the SI to the dorsal body wall, Mesocolon/rectum from the LI to the dorsal body wall, Greater omentum from the greater curvature of stomach, draping over SI, to dorsal body wall; Lesser omentum from the lesser curvature of stomach to liver.

8.Hard palate (palatine bones & palatine process of maxilla), tongue, cheeks, soft palate

9.Labial frenulum from inner lips to gums, lingual frenulum from lower tongue to floor of mouth, bolus is ball of food ready to swallow, papillae are bumps on tongue including taste buds

10.Skeletal muscle and mucous membrane

11. Taste buds are at base of taste pores, so you need liquid to reach them.

12.Parotid, submandibular, sublingual

13.Lubricate & moisten food & kill bacteria, mostly water plus lysozyme, amylase & mucins; PNS & food & mouth irritation increase salivation, SNS & fear & dehydration decrease salivation


15.Cementum is bone-like material covering root, enamel is calcified hard covering of crown, pulp cavity is where blood vessels and nerves are present; Dentin is bone-like material comprising the bulk of the tooth, crown is part of tooth showing in the mouth, root is part not showing embedded in jaw alveoli; neck is junction at gum line between root and crown; apical foramen is hole in the root for entry/exit of nerves and blood vessels; periodontal ligament holds root into the alveoli.


17. Labial is nearest lips, buccal is nearest cheek, lingual is nearest tongue, palatal is nearest palate & occlusal is chewing surface


19.Ingestion is eating, mastication is chewing, deglutition is swallowing.

20.Pharynx is throat, esophageal hiatus is hole in diaphragm for esophagus to pass into abdominal cavity; peristalsis is wavelike rippling contraction, and esophagus has circular muscles at superior & inferior ends.

21.Transport food

22.Cardiac region is where esophagus enters into stomach, fundus is storage pouch to the left of cardia, body is majority of stomach, pylorus is inferior end of stomach. Convex border is greater curvature, concave border is lesser curvature

23.Gastroduodenal junction

24.Parietal cells make HCl; mucus cells make mucus; Zymogenic cells make pepsinogen


26.Liquefied food

27.Pacemaker cells cause waves of peristalsis from cardia to pylorus. If sphincter is closed, the chyme is pushed back towards the cardia and the process starts again.

28.Presence of food (eating, thinking about) stimulates motility. Gastrin, made by pylorus, stimulates motility. Certain foods can stimulate motility more than others. Caffeine stimulates gastrin release.

29. Enterogastric reflex inhibits motility. A distended duodenum causes the release of GIP, cholecystokinin & secretin which inhibit gastric motility.

30.Mucus is so important because it protects the stomach lining from the powerful acid. HCl serves to inhibit microorganism growth & breakdown proteins. Pepsinogen is converted to an active pepsin in the acid environment which breaks down proteins.

31.Same as for motility, see #28

32.Same as for motility, see #29

33.Very little

34.Gastrin stimulates gastric motility & secretions & is released by stomach (pylorus) cells in response to distention. The other hormones are released by the duodenum in response to distention & inhibit gastric motility & secretions.

35.Pancreas is inferior to stomach and the duct travels from pancreas to the beginning of the duodenum

36.Islets are the hormonal part of the pancreas – substances include insulin & glucagon

37.Acinar cells

38.Water, Bicarbonate, Amylase, Lipase, Proteases (carboxypolypeptidase, trypsin, chymotrypsin)

39.First three are proteases, amylase breaks down carbohydrates (starch), and lipase breaks down fat

40.Vagus nerve (PNS) stimulates secretions & SNS inhibits it. Secretin, Cholecystokinin stimulate pancreatic secretions.

41.Liver cell

42.Liver has hepatic duct & gall bladder has cystic duct that join together forming the common bile duct which dumps into the beginning of the duodenum


44.Store bile

45.Water, bile salts, bilirubin

46.Bile salts serve to emulsify fats which physically breaks them into smaller pieces so that they can be worked on by the lipases. The bile salts are recycled by being reabsorbed from the ileum, and returned to the liver to make more bile.

47.Enterohepatic circulation stimulates bile secretion as does vagus nerve, as does secretin & cholecystokinin

48.Make bile, detoxify, store nutrients, vitamins & poisons, metabolic hub, get rid of old blood cells, makes blood proteins and clotting factors

49.Duodenum, jejunum, ileum

50.Villi are finger-like extensions of the intestinal mucosa which increase surface area available for absorption. Microvilli are small ones. Brunner’s gland secrete mucus.

51.Intestinal lymph vessel to absorb large particles that cannot fit into blood capillaries, such as fats & proteins.

52.Segmentation is a stationary contraction that mixes the contents & breaks it into littler chunks; peristalsis is a wave – like contraction moving contents inferiorly.

53.Broken-down food passes from intestinal lumen into lymph or blood vessels. Most occurs in small intestine.

54.Carbohydrates are broken down from saliva & again in duodenum from pancreatic amylase. It absorbs by active transport into blood capillaries. Proteins are broken down in stomach (HCl & Pepsin) and further by pancreatic proteases. Amino acids are absorbed into blood vessels. Lipids are emulsified by bile salts, broken down by lipases forming a micelle. Micelle passes through intestinal wall & further broken down & bile salts released for recycling forming a chylomicron which is absorbed into lacteal. Vitamins ADEK are absorbed with lipids & Bs and C are absorbed with the water. A tremendous amount of water is absorbed (9l/day) and electrolytes are absorbed too. Calcium ions require vitamin D for absorption. An electrolyte is a chemical that ionizes when in solution.

55.See above.

56.Cecum & with appendix are closest to ileum. They are lower right abdomen. Then the colon ascends, transverses, descends and has a sigmoid (S shaped) turn before entering into the pelvic cavity at which point it becomes the rectum. The rectum opens at the anus which is a series of two sphincters.

57.Haustra are pouches of LI and taeniae coli are LI muscular bands on the surface of the colon

58.The gastroileal reflex occurs when the stomach is full of food, the ileum releases its contents into the LI. This causes peristalsis of the LI. A couple of times per day, a huge peristalsis occurs in LIĀ forcing contents into rectum. This stretches the wall of the rectum leading to the defecation reflex in which case the internal anal sphincter relaxes and the person has the urge to defecate. Haustral churning is contraction of the colon resulting in mixing & more importantly dividing the contents into smaller pieces in the haustra.

59.External anal sphincter is voluntary skeletal muscle

60.Solid waste

61.Form & store feces. Lubricate feces due to numerous goblet cell secretions. A speck of water absorption, Vit B/K synthesis