KEY CHAPTER 17: DIGESTIVE SYSTEM

OBJECTIVES

1. Name the organs and function of the digestive system.

ORGANS FUNCTION

Mouth

To breakdown food into substances that

can be absorbed and used for energy.

Pharynx

Esophagus

Stomach

Small intestine

Large intestine

Salivary glands

Pancreas

Liver

Gallbladder

2. Define the term digestion and explain its significance.

The breakdown of food or nutrients to small substances that can be absorbed for cellular

respiration = energy.

3. Distinguish between mechanical (i.e. physical) digestion and chemical digestion.

Mechanical – mouth with chewing and breaking into smaller pieces; stomach with

mixing

Chemical – digestion of macromolecules by enzymes into smaller building blocks.

4. Discuss the five digestive processes that overview the many functions of the digestive

system.

Ingestion, Mechanical digestion( mouth, stomach), Propulsion (swallowing, peristalsis),

Chemical digestion, Absorption, Defecation.

5. Distinguish between the alimentary canal and digestive accessory organs, and label each

on the diagram below.

Alimentary canal – from mouth to anus: Oral cavity, pharynx, esophagus, stomach, small

intestine, large intestine. These organs “see” the food.

.

Accessory organs – Salivary glands, liver, gallbladder, and pancreas. These organs

secrete enzymes or substances into “food” to assist with its chemical digestion.

6. Name two synonyms for the alimentary canal.

Digestive Tract , GI Tract

7. Name the four layers that compose the wall of the alimentary canal from innermost

(lining lumen) to outermost, and label each in the diagram below.

Mucosa

Submucosa

Muscularis

Serosa

8. Compare and contrast the four layers of the alimentary canal wall (named above) in terms

of their structure, function, and any distinguishing features.

Mucosa- Epithelium, CT, Smooth muscle- protection, secretion, absorption.

Submucosa- LACT, Blood Vessels, Lymphatic Vessels, Nerves - nourishes mucosa and

carry away absorbed nutrients.

Muscularis- two layers of smooth muscle, inner circular and outer longitudinal =

movement of tube through mixing and peristalsis.

Serosa- SSET over LACT- lubrication and cushioning. Also called the visceral

peritoneum.

9. Name the layer of the alimentary canal that is synonymous with visceral peritoneum.

Serosa- function in lubrication and cushioning

Copyright 2011 Dr. Mary Cat Flath

submucosal

myenteric

10. Explain the significance of mesentery or peritoneal extensions.

The small intestine is suspended in the abdominal cavity by mesentery

11. Describe how food is moved through the length of the alimentary canal (b below) and

name the layer responsible for these actions.

a. Mixing – mechanical digestion in mouth and stomach

b. Peristalsis – interaction between circular and longitudinal layers which move food

through the alimentary canal

12. Define the term digestive sphincter muscle, describe the structure of these muscles, name

the function of these muscles, and denote the major five locations of digestive sphincter

muscles in the diagram below.

A sphincter muscle is a circular muscle that prevents regurgitation of food between

portions of the alimentary canal.

- Gastroesophageal Sphincter lies between the esophagus and stomach/

- Pyloric Sphincter lies between the stomach and small intestine.

- Ileocecal valve lies between the small and large intestine.

- Anal Sphincters - Internal and External, lie between anus and outside

13. Name two synonyms for the mouth.

Oral Cavity

Buccal Cavity

14. Describe the overall structure and function of the mouth, and label the major parts in the

diagram below.

The mouth is structured as a food receptacle and it’s surrounded by powerful cheek

muscles and the tongue. It houses teeth which mechanically digest ingested food.

It is also the first site of carbohydrate digestion: Salivary amylase- chemically digests

polysaccharides (glycogen and starch) into disaccharides.

.

15. Discuss the three portions of the palate, in terms of location (these should already be

labeled above) and give an overall function for the palate.

Hard Palate, Soft Palate, Uvula

The palate separates the oral cavity from the nasal cavity.

16. Name the tissue that composes the tonsils, label them above, and name the overall

function of tonsils.

Palatine tonsils- masses of lymphatic tissue- lateral to palate

Pharyngeal tonsils- adenoids lymphatic on posterior pharynx

Tonsils function to filter out and destroy debris and foreign agents ingested. They are

part of the lymphatic system which controls disease.

17. Name the two sets of teeth we possess as humans, discuss the general structure of a tooth

and label each in the lower diagram below, and describe the four types of teeth we

possess according to their location and function, and label each in the upper diagram.

Deciduous Teeth Permanent Teeth

0. Number 20 1. Number 32

1. Erupt from 6-22 months 2. Erupt from 6yrs- adult hood

2. Lost between 6-12 years

Function: To break food into smaller

Pieces (mechanical digestion)

18. Name and locate the three sets of salivary glands in humans (see below), name and

describe the secretions from these glands, and name the two types of cells that compose these

glands.

Parotid- largest lies over masseter, mostly serous cells - clear, watery serous fluid (with

amylase).

Submandibular- floor of mouth lateral, mix of serous (with amylase) and mucous cells

Sublingual- floor of mouth, medially, mostly mucous cells

19. Discuss the enzyme "salivary amylase", in terms of its digestive function, location of its

activity, and secretory gland.

Enzyme – salivary amylase breaks polysaccharides into disaccharides

A. Starch – disaccharides B. Glycogen – disaccharides

20. Explain the process of deglutition using the diagram below.

Deglutition- swallowing

A) The tongue forces bolus of food into pharynx

B) The soft palate and larynx are raised, the tongue is pressed against palate, and the

epiglottis closes.

C) Superior constrictor muscles contract and force food into the esophagus.

D) Peristaltic wave move food through the esophagus to the stomach

21. Name the function of the epiglottis, and label it in the diagram above.

The epiglottis closes off the airway during swallowing.

22. Define the term peristalsis and explain its digestive function.

A) Accomplished by movements down the longitudinal muscle layer propelling

action. B) As food passes, one section of the tube relaxes opening next section

food moves on.

23. Name the tube that carries food from the mouth to the stomach and label it in the diagram

below.

Esophagus

24. Define the term gastric.

Stomach

25. Describe the macroscopic structure of the stomach and locate each portion in the diagram

below and on the torso model.

J- shaped pouch like organ contains extra oblique layer in muscularis under diaphragm

left side.

Proximal cardiac region, ballooned fundic region, and distal pyloric region. Greater

curvature versus lesser curvature and bulk is called the body.

26. Name the term used to describe the mucosal folds of the stomach lining and explain their

significance.

Rugae

27. Discuss the histology of the stomach wall.

Gastric villi form gastric pits are lined by gastric glands with Chief cells, (pepsin),

Parietal cells (HCl and Intrinsic Factor), Mucous cells (mucus) and G-Cells (gastrin).

28. Name the five types of cells that compose gastric glands, name the secretion(s) that each

cell produce(s) that together compose gastric juice, identify each on the diagram below,

and give the function of each component of gastric juice.

Gastric pits are lined by gastric glands. Gastric glands secrete gastric juice; Gastric glands

are composed of four types of cells: 1) chief cells secrete enzyme pepsin. 2) Parietal cells

secrete hydrochloric acid and intrinsic factor. 3) Mucous goblet cells secrete mucus. 4)

G- cells secrete hormone Gastrin.

29. Define the term chyme.

Food plus mixing with gastric juices.

230. Name one substance that is absorbed through the gastric mucosa.

Toxins, alcohol, some vitamins are absorbed.

31. Name the hormone that regulates the release of gastric juice, circle it in the diagram

below, name the cell that secretes it, explain when it is released, and the results of its

action.

When food enters the stomach, G-cells secrete the hormone gastrin. Gastrin travels

through the bloodstream and targets gastric glands. Gastrin stimulates glands to release

more gastric juice rich is pepsin, HCl, etc. It also stimulates mixing action and constricts

the gastroesophageal sphincter and over time, relaxed the pyloric sphincter.

32. Using anatomical terminology, describe the location of the pancreas in the abdominal

cavity, and label it below.

Pancreas is posterior to stomach.

Copyright 2011 Dr. Mary Cat Flath

(of Vater) (of Oddi)

33. Explain how the pancreas aids in digestion by listing the components in pancreatic juice,

and naming the action of each of those components.

The pancreas secretes pancreatic juice containing amylase, proteinases, lipases, and

nucleases into duodenum. These enzymes work in the duodenum and break down

polysaccharides, proteins, triglycerides, and nucleic acids, respectively.

34. Name the site of pancreatic enzyme action, and label it in the diagram above.

Duodenum

35. Name the regulatory hormone responsible for the release of pancreatic juice into the

duodenum, explain when it is activated, and circle its name in the diagram below.

Secretin. It is released from the intestinal mucosa when acidic chime enters. It travels

through the bloodstream and targets the pancreas to release of its bicarbonate rich

pancreatic juice into duodenum.

Copyright 2011 Dr. Mary Cat Flath

36. Define the term hepatic.

liver

37. Using anatomical terminology, describe the location of the liver in the abdominal cavity,

and label it in the diagram below.

Upper right quadrant below diaphragm.

38. Name the functional unit of the liver and describe its general structure as seen in diagram

(a) below.

The functional unit of the liver is the hepatic lobule.

39. Define the terms hepatocyte and liver sinusoids, and label each in diagram (b) above.

Hepatocytes- liver cells; which provide most functions.

Liver sinusoids- liver capillaries. Blood enters and hepatocytes remove oxygen,

nutrients, poisons, worn cells, and debris.

40. Describe the many functions of the liver.

Produces bile (digestive function = emulsification of fat), filter blood of toxins and

debris, metabolizing of all simple nutrients, and storage of glycogen, iron, and more.

41. Name the two blood vessels that supply the liver lobules with blood and track the flow of

blood into and out of the liver lobule.

Hepatic Artery Hepatic portal vein

Hepatic Artery Hepatic Portal Vein

(Oxygenated Blood) (Deoxygenated Blood with

from aorta) newly absorbed nutrients

from Small intestine, etc.)

Liver Sinusoids

(Exchange)

Central Vein of Hepatic Lobule

Hepatic Vein

Inferior Vena Cava

42. Name the components of a portal triad, and label them in the diagram 38b above.

Branch of hepatic artery, branch of hepatic portal vein, and a bile duct.

43. Explain the significance and location of Kupffer's cell.

Macrophages in liver tissue which filter and destroy debris and worn cells from blood

through phagocytosis. They are part of the lymphatic system and help control disease.

44. Define the term emulsification and explain its role in digestion.

Emulsification = breaking large fat globules into small fat droplets, increasing surface

area so lipases can work more effectively. Bile is released into duodenum through

common bile duct. It emulsifies fat and also aids in absorption of fat and fat soluble

vitamins.

45. Using anatomical terminology, describe the location of the gallbladder in the abdominal

cavity and label it in diagram 36 above and in the diagram below.

Inferior to liver.

46. Name the function of the gallbladder.

Stores bile between meals.

47. Name the "common" route that bile travels from either the liver or gallbladder, name the

site where bile is deposited, and label each in the diagram below.

Bile is deposited into duodenum from either the liver or gallbladder. The cystic duct

from the gallbladder and the hepatic duct from liver come together to form the common

bile duct. There is a valve that keeps the common bile duct closed until it is stimulated

with CCK below.

48. Name the regulatory hormone that is responsible for the release of bile into the duodenum

explain when it is activated, and circle its name in the diagram below.

When fatty chyme enters the duodenum the intestinal mucosa release the hormone

cholecystokinin (CCK) into the bloodstream. CCK targets the gallbladder and causes

contractions that cause the deposition of bile into the duodenum.

49. Name the three parts of the small intestine, and locate each on the diagram below and on

the torso model.

Duodenum

Jejunum

Ileum

50. Discuss the histology of the small intestinal wall.

Macroscopic villi with mucosa, submucosa, muscularis, and serosa. Mucosa lining is

simple columnar epithelium and contains goblet cells and microvilli = protection,

secretion, and absorption. Submucosa with blood vessels carries away absorbed

nutrients. Muscularis functions in peristalsis. Serosa (SSET/LACT) provides lubrication

and cushioning.

51. Name the digestive enzymes that are secreted by the mucosa of the small intestines and

explain the action of each.

Duodenal mucosa secretes lactase, sucrase, and maltase, which break disaccharides into

monosaccharides; peptidases which break peptides into amino acids; lipases which

continue to clip two fatty acids off triglycerides, leaving monoglyceride and 2 fatty acids.

52. Identify the simplest forms of food that are absorbed through the mucosa of the small

intestine, name the transport process by which each is absorbed, and describe the fate of

each absorbed nutrient.

Monosaccharides are absorbed by facilitated diffusion (and active transport). They are

carried away by submucosal blood capillaries into the bloodstream (i.e. mesenteric vein

to hepatic portal vein to liver).

Amino acids are absorbed by active transport. They are carried away by submucosal

blood capillaries into the bloodstream (i.e. mesenteric vein to hepatic portal vein to liver).

Fatty acids and monoglyceride are absorbed by simple diffusion into intestinal mucosa.

They are recombined into chylomicrons that are absorbed by a lacteal into the lymphatic

system.

53. Define the term lacteal, explain its significance, and be able to identify the lacteal below.

Lymphatic capillaries in each intestinal villus that absorb dietary fat.

54. Distinguish between the duodenum and the distal small intestine (i.e. jejunum and ileum)

in terms of function. Review the location of each in diagram 48 above.

Duodenum (proximal) = site of completion of digestion.

Jejunum = bulk of intestinal length = site of absorption of simple nutrients.

Ileum (distal) = distal end which meets with cecum of large intestine.

55. Name the four parts of the large intestine and locate each on a diagram or torso model.

1. Cecum 3. Rectum

2. Colon

3. Anus

56. Name the four parts of the colon and locate each on the diagram below and on the torso

model.

Ascending colon (right side)

Transverse Colon (across from right to left)

Descending Colon (left side)

Sigmoid Colon (back to center)

57. Identify the major functions of the large intestine.

Reabsorption of water and electrolytes.

58. Explain how the movements in the large intestine differ from those throughout the rest of

the alimentary canal.

Mass movements only 2-3 times daily. Peristaltic waves of large intestine move residual

chyme toward anal sphincter muscles.

59. Define the terms feces and defecation.

Feces = undigested and unabsorbed material.

Defecation = emptying of solid wastes from rectum.

60. Name the sphincter muscles that open to the outside and explain how their action is

controlled.

Internal and External anal sphincters.

61. List the four major organic macromolecules that we ingest, and explain how each is

broken down by various enzymes within the alimentary canal. Be sure to include enzyme

names, the location of enzyme action, and the breakdown products that result from the

enzymatic action, and explain any hormonal control of the breakdown. Finally, explain

how and where these simplest food forms are absorbed into the bloodstream or lymphatic

system.

DIGESTIVE SYSTEM SUMMARY TABLE II (Keyed at the end of this exercise) MACRO-

MOLECULE

INGESTED

SITE OF

DIGESTION

DIGESTIVE

ENZYME(S)

END-PRODUCT(S)

SITE AND MODE

OF ABSORPTION

ABSORBED INTO

BLOOD OR

LYMPH

REGULA-TION

MACRO-

MOLECULE

INGESTED

CARBO-

HYDRATES

PROTEINS

FATS (TRI-

GLYCERIDES

OR TG)

NUCLEIC

ACIDS

SITE OF

DIGESTION

1.MOUTH

2.DUODENUM

3.DUODENUM

1.STOMACH

2.DUODENUM

3.DUODENUM

1. DUODENUM

2. DUODENUM

DUODENUM

DIGESTIVE

ENZYME(S)

1. SALIVARY

AMYLASE

2. PANC.

AMYLASE

3. SUCRASE,

LACTASE,

MALTASE

1.PEPSIN

(HCl)

2. PANC.

PROTEASES

3.

PEPTIDASES

1.

PANCREATIC

LIPASES

*BILE

2. DUODENAL

LIPASES *BILE

PANCREATIC

NUCLEASES

END-PRODUCT

(S)

1 & 2.

STARCH AND

GLYCOGEN

TO DISAC-

CHARIDES

3. DISACCHA-

RIDES TO

MONOSAC-

CHARIDES

1. HCl

DENATURES

PROTEINS

1 & 2.

PROTEINS TO

PEPTIDES

3. PEPTIDES

TO AMINO

ACIDS

BILE

EMULSIFIES

TG’S.

PANCREATIC

LIPASES

BREAK TG’S

INTO FATTY

ACIDS &

MONOGLY-

CERIDES;

DUODENAL

LIPASES

BREAK TG’S

INTO FATTY

ACIDS

GLYCEROL

NUCLEO-

TIDES

SITE AND MODE

OF ABSORP-TION

DISTAL SM.

INTESTINE ;

FACILI-

TATED

DIFFUSION

DISTAL SM.

INTESTINE;

ACTIVE

TRANSPORT

DISTAL SM.

INTESTINE

SIMPLE

DIFFUSION

DISTAL SM.

INTESTINE

ABSORBED INTO

BLOOD OR LYMPH

BLOOD

BLOOD

LYMPH BY

LACTEAL

BLOOD

REGULATION

SECRETIN

GASTRIN ;

SECRETIN

CCK FOR BILE;

SECRETIN ;

SECRETIN