GI anatomy Flashcards
(27 cards)
structure of GI tract
7 continuous meters from mouth to anus
begins to form as early as 4th week of gestation
function of GI tract
provide nutrients for the body with propulsive and mixing movements
secretion of digestive juices
absorption of nutrients
esophagus
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
esophageal sphincters
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
stomach
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
mucosa layer of stomach
inner layer made up of G cells, parietal, chief, and epithelial cells
contains blood vessels
muscle layers of the stomach
TWO
help propel food from stomach to small intestine
serosa layer of stomach
outer layer
acts as covering for inner layers
G cells
produce gastric – produces HCl
parietal cells
produce HCl acid to help break down food
produce IF to protect mucosa
chief cells
secrete pepsin
epithelial cells
secrete bicarbonate-rich solution to coat and protect mucosa
smalll intestine
approx 5-6m long
duodenum (first 22cm)
jejunum (next 2 meters [200cm])
ileum (~300; remainder)
small intestine
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
cells of small intestine
crypts of lieberkuhn
goblet cells and Brunner glands
have a rapid turnover (48-72hr) – one of fastest in body
crypts of lieberkuhn cells
intestinal glands that secrete ~ 2L of fluid per day into lumen in SI
fluid is quickly reabsorbed by villi
goblet cells and brunner glands
secrete large amounts of mucus to protect SI from damage of acidic gastric juices
ileoceccal sphincter
area where food passed from small to large intestine
distention of terminal ileum
causes relaxation to allow contents to enter large intestine
distention fo cecum
prevents reflux back into ileum
large intestine
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
cells of LI
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
motility of the GI tract
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
function of esophagus
transport food
