Digestive Tract

Question 1

what are the 4 layers of the digestive tract?

Answer 1

mucosa, submucosa, muscularis externa, and serosa/adventita

Question 2

what are the 3 components of the mucosa

Answer 2

epithelium- simple columnar throughout (except mouth pharynx, esophogus, anus). lamina propria- CT lying between epthelium and muscularis mucosa. muscularis mucosa- thin layer of smooth muscle

Question 3

what is the submucosa

Answer 3

layer between muscularis mucosa and muscularis externa

Question 4

what is the serosa/adventitia

Answer 4

external layer. serous is it is a visceral membrane. adventitia if it is against another organ.

Question 5

what is the epithelial structure of the esophogus?

Answer 5

stratified squamous nonkeratinized

Question 6

describe the muscularis externa in the esophogus

Answer 6

proximal third is skeletal, smooth muscle in the distal third

Question 7

where in the GI tract change from stratified squamous to simple columnar?

Answer 7

gastro-esophogeal junction

Question 8

what does the pH of the stomach need to be so low?

Answer 8

because the enzymes that break down food require it

Question 9

how does the stomach protect itself from the pH

Answer 9

surface mucous cells line the entire stomach and gastric pits, producing a mucous that is alkaline and protective

Question 10

what 3 cells are found in the deep gastric layers, or gastric glands?

Answer 10

parietal cells- create acidic environment and secrete intrinsic factor, cheif cells- secrete pepsinogen, lipase, and leptin. enteroendocrine cells- secrete gastrin, VIP, serotonin

Question 11

describe which cell creates the acidic environment and how

Answer 11

parietal cells- contain carbonic anhydrase which combines co2 and h2o into h2c03 which dissociates into hco3 and H. the H gets pumped into stomach in a ATP dependent manner.

Question 12

describe the muscularis externa in the stomach

Answer 12

3 layers

Question 13

describe the “neck” cells in the gastric pits

Answer 13

stem cells and mucous neck cells which produces a different mucous then the surface cells

Question 14

what ligament marks the end of the duodenum

Answer 14

ligament of treitz

Question 15

what is the “identifying” feature of the duodenum?

Answer 15

submucosal glands of Brunner- alkaline secretions

Question 16

what does the duodenum do?

Answer 16

receive secretions from the pancrease, stomach, and bile duct to prepare food for digestion

Question 17

plicae circulares

Answer 17

grossly visible folds of small intestine

Question 18

describe the folding heiarchy in the small intestines

Answer 18

plicae circulares, villi, microvilli

Question 19

how do muscles contribute to an extended contact time between food and small intestine

Answer 19

muscularis mucosa move villi back and forth. muscularis externa moves food back and forth

Question 20

where is the point of maximal absorption

Answer 20

proximal jejunum

Question 21

describe the anatomy of a villi

Answer 21

it is a small fold lined by columnar epithelium. the core is comprised of capillaries and lymphatics, nerves, and smooth muscle. at the bottom of the villi are the crypts, where basal cells generate new cells that move towards the top as they age.

Question 22

paneth cells

Answer 22

found in the crypts of villi and secrete lysozymes to fight bacterial infection

Question 23

is there a difference in absorption of different materials?

Answer 23

yes- monosaccarides and amino acids enter capillaries. fats enter lymphatics

Question 24

peyers patches

Answer 24

collectoins of lymphoid tissue with specialized m cells. these endocytose antigens to enable an immune response.

Question 25

what does the ileum do besides absorb food?

Answer 25

absorb intinsic factor bound vitamin b12 and reabsorb bile

Question 26

what is the main function of the colon

Answer 26

reabsorb water. however, most water is reabsorbed in the colon.

Question 27

are there villi in the colon?

Answer 27

no

Question 28

how is the muscluris externa different in the colon

Answer 28

confined to 3 longitudinal bands called the taeniae coli

Question 29

haustra

Answer 29

bulges of colon

Question 30

describe the function of the appendix

Answer 30

none known. there is a lot of lymphoid tissue hinting at immunologic function, but it cannot be proven

Question 31

how long is the rectum? where does it end?

Answer 31

12 cm and ends at pelvic diaphragm

Question 32

what are the longitudinal folds in the rectum?

Answer 32

smooth muscle. they are called the rectal columns of morgagni

Question 33

how is the smooth muscle situated in the rectum

Answer 33

circumferentially

Question 34

enteric nervous system

Answer 34

can function autonomously, but receives input from both sympathetic and parasympathetic. ganglia found in meissners plexus, (submucosa) and auerbacks plexus (muscularis externa)