GI anatomy

Question 1

structure of GI tract

Answer 1

7 continuous meters from mouth to anus
begins to form as early as 4th week of gestation

Question 2

function of GI tract

Answer 2

provide nutrients for the body with propulsive and mixing movements
secretion of digestive juices
absorption of nutrients

Question 3

esophagus

Answer 3

tube shaped muscular conduit for food and fluids that connects throat to stomach

movement facilitated by secretion of mucus, very strong muscle movement to propel food towards stomach

Question 4

esophageal sphincters

Answer 4

bundles of muscle that prevent food from coming back up (closed @rest)

UES: prevents food/fluids from being aspirated into lungs

LES (cardiac sphincter) separates esophagus from stomach and prevents acidic contents of stomach from entering back into esophagus

Question 5

stomach

Answer 5

reservoir for food, mixing and initial digestion of proteins

normal capacity: 1000-1500mL

lined with columnar epithelium containing millions of gastric glands –> contain cells that secrete HCl, IF, and gastrin

Question 6

mucosa layer of stomach

Answer 6

inner layer made up of G cells, parietal, chief, and epithelial cells
contains blood vessels

Question 7

muscle layers of the stomach

Answer 7

TWO
help propel food from stomach to small intestine

Question 8

serosa layer of stomach

Answer 8

outer layer
acts as covering for inner layers

Question 9

G cells

Answer 9

produce gastric – produces HCl

Question 10

parietal cells

Answer 10

produce HCl acid to help break down food
produce IF to protect mucosa

Question 11

chief cells

Answer 11

secrete pepsin

Question 12

epithelial cells

Answer 12

secrete bicarbonate-rich solution to coat and protect mucosa

Question 13

smalll intestine

Answer 13

approx 5-6m long

duodenum (first 22cm)
jejunum (next 2 meters [200cm])
ileum (~300; remainder)

Question 14

small intestine

Answer 14

entire inner wall has circular folds of mucous membrane (place circulares)
^ they are permanent ridges that contain millions of fingerlike projections (intestinal villi)

each villus has its own microscopic projections - microvilli

^^combined effect of circular folds, villi, and microvilli increase SA for digestion x 600

Question 15

cells of small intestine

Answer 15

crypts of lieberkuhn
goblet cells and Brunner glands

have a rapid turnover (48-72hr) – one of fastest in body

Question 16

crypts of lieberkuhn cells

Answer 16

intestinal glands that secrete ~ 2L of fluid per day into lumen in SI
fluid is quickly reabsorbed by villi

Question 17

goblet cells and brunner glands

Answer 17

secrete large amounts of mucus to protect SI from damage of acidic gastric juices

Question 18

ileoceccal sphincter

Answer 18

area where food passed from small to large intestine

Question 19

distention of terminal ileum

Answer 19

causes relaxation to allow contents to enter large intestine

Question 20

distention fo cecum

Answer 20

prevents reflux back into ileum

Question 21

large intestine

Answer 21

1.5 m long
muscular tube that forms frame around SI
6.5 cm in diameter (greater than SI; hence name)

includes appendix, ascending colon, transverse colon, descending colon, sigmoid colon and rectum

Question 22

cells of LI

Answer 22

NO villi & doesnt produce digestive enzymes

absorptive cells absorb water and electrolytes

goblet cells produce mucous

endocrine cells are present and produce hormones (fxn not understood)

turnover of large intestine cells is 3-8 days

Question 23

motility of the GI tract

Answer 23

d/t contractions of 2 layers of smooth muscle (longitudinal and circular)

2 types:
propulsive (peristalsis)
mixing (segmental)

motility is regulated by the enteric nervous system, ANS, and hormones

Question 24

function of esophagus

Answer 24

transport food

Question 25

function of stomach

Answer 25

store and churn food
pepsin digests protein
HCl activates enzymes, breaks up foods, kills germs
mucus protects stomach wall
limited absorption

Question 26

function of small intestine

Answer 26

completes digestion
mucus protects gut wall
absorbs nutrients, most water
peptidase digest pro
sucrases digest sugar
amylase digest polysaccharides

Question 27

function of large intestine

Answer 27

reabsorb water
form and store feces