Digestion III Study Guide

Question 1

three subdivisions of the SI in order from proximal to distal.

Answer 1

Duodenum
Jejunum
ileum

Question 2

diameters and lengths of the SI and LI.

Answer 2

Large intestine: diameter = 2.8 inches, length = 5 feet
Small intestine: diameter = 1-1.6 inches, length = 7-13 feet (20 in a cadaver)

Question 3

circular folds

Answer 3

Permanent folds in the SI; bumps to slow/alter the flow of chyme

Question 4

villus

Answer 4

contains Dense capillary bed and a lacteal (lymphatic vessel of the SI that absorbs digested fats)

Question 5

brush border

Answer 5

The fuzzy appearance of the microvilli (cytoplasmic extensions of each mucosal cell)

Question 6

role of brush border

Answer 6

Brush border’s enzymes complete final carbohydrate + protein digestion

Question 7

5 types of cells found in SI’s villi and crypts

Answer 7

enterocytes, goblet cells, enteroendocrine, paneth cells, stem cells

Question 8

Enterocytes

Answer 8

make up the bulk of the epithelium
- In the villi, absorb nutrients and electrolytes
- In the crypts, product intestinal juice

Question 9

Goblet cells

Answer 9

secrete mucus in the villi and crypts

Question 10

Enteroendocrine

Answer 10

source of enterogastrones - hormones that inhibit secretion

Question 11

. Paneth cells

Answer 11

secretory cells found deep in the crypts - secrete antimicrobial agents

Question 12

Stem cells

Answer 12

continuously divide to produce other cell types - epithelium is renewed every 2-4 days

Question 13

Peyer’s patches

Answer 13

aggregate lymphoid nodules, located in the lamina propria (in MALT)
- Found in greater numbers in the distal SI - along with large numbers of IgA secreting plasma cells

Question 14

Duodenal glands

Answer 14

(in submucosa)
Secrete alkaline mucus to neutralize acidic chyme and prevent duodenal ulcers

Question 15

Intestinal juice

Answer 15

• 1-2L are secreted daily in response to distension or irritation of the mucosa
• Production stimulated by acidic chyme
• Slightly alkaline, isotonic with blood plasma
• Largely water + mucus from the duodenal glands and goblet cells

Question 15

digestive juice

Answer 15

very acidic, breaks down proteins and starches

Question 16

Why is the slow pace of chyme entering the SI crucial?

Answer 16

• Chyme entering the duodenum is hypertonic – to avoid water loss from blood, chyme entry must be slow
• Additionally, acidic chyme must be neutralized
• It takes time for chyme to be mixed with bile and pancreatic juices

Question 17

Gastroileal Reflex

Answer 17

a long neural reflex triggered by stomach activity – force of segmentation is increased in the ileum and the ileocecal valve relaxes

Question 18

Gastrin

Answer 18

increases motility and relaxes the ileocecal valve

Question 19

key functions of the LI

Answer 19

reabsorb most of the remaining water from indigestible food residue, temporarily store residue, absorb metabolites produced by resident bacteria, and eliminate residue from the body as semisolid feces
- produces vitamin b’s and k

Question 20

Teniae Coli

Answer 20

3 bands of longitudinal smooth muscle in the muscularis

Question 21

Haustra

Answer 21

pocketlike sacs caused by the muscular tone of the teniae coli
Contractions of the LI are weak, sluggish compared to the SI

Question 22

Haustral Contractions

Answer 22

primary contractions of the colon; slow, segmenting movements primarily in the ascending and transverse colon; haustra sequentially contract in response to distension

Question 23

Epiploic Appendages

Answer 23

fat-filled pouches of visceral peritoneum

Question 24

Appendix

Answer 24

contains masses of lymphoid tissue
- Part of MALT
- Storehouse for bacteria, capable of recolonizing gut when necessary
- Susceptible to blockages because of twisted shape

Question 25

external anal sphincter

Answer 25

voluntary control

Question 26

roles of the goblet cells, stratified epithelium in the LI

Answer 26

• LI contains a thicker mucosa than the SI – it is made of simple columnar epithelium EXCEPT for stratified squamous epithelium in the anal canal
• Mucosa contains abundant deep crypts with many mucus-producing goblet cells
• No circular folds, villi, or digestive secretions

Question 27

internal anal sphincter

Answer 27

involuntary control

Question 27

Anal Columns

Answer 27

mucosa of the anal canal hangs in long ridges/folds

Question 28

gut microbiome

Answer 28

1000+ types of bacteria
functions
- Fermentation: bacteria ferment indigestible carbohydrates and mucin – results in short chain fatty acids that are used for fuel; fermentation produces a mixture of gases (~500mL/day)
- Vitamin Synthesis: bacteria synthesize B complex vitamins and some of the vitamin K needed by the liver to produce clotting factors

Question 29

gut microbiome affect on health

Answer 29

• Body weight
• Susceptibility to various diseases – diabetes, atherosclerosis, fatty liver disease
• Allergies
• Moods/mental health

Question 30

Gastrocolic Reflex

Answer 30

initiated by the presence of food in the stomach; causes mass movements: slow, powerful peristaltic waves that are activated 3-4 times/day
- The descending and sigmoid colon act as storage reservoirs
- Increased dietary fiber strengthens colonic contractions and softens feces

Question 31

Diverticula

Answer 31

herniations of mucosa through the colon’s walls

Question 32

diverticula cause

Answer 32

A low-fiber diet can result in low residue volume and a narrowed colon – contractions became more powerful and increase pressure on the colon’s walls

Question 33

Diarrhea

Answer 33

watery, loose stools; LI does not have time to absorb remaining water
- Causes: irritation of the colon by bacteria, jostling of digestive viscera
- Prolonged diarrhea may result in dehydration and electrolyte imbalances

Question 34

Constipation

Answer 34

food residue remains in the colon for extended periods of time; too much water is absorbed
- Stool becomes hard and difficult to pass
- Causes: insufficient fiber and/or fluid in the diet, improper bowel habits, lack of exercise, or laxative abuse