Histo of SI and LI Flashcards
SI structure and function
complete chemical digestion neutralize acidic chyme segmentation contractions absorb majority of nutrients secrete mucous secrete CCK, VIP and secretin
chyme
semifluid mass of partly digested food expelled by the stomach into the duodenum
plicae circulares
permanent folds of mucosa and submucosa
begin in the duodenum distinct in the jejunum disappear in mid ileum
intestinal villi
finger like projections of the mucosa covering the entire surface of the SI
increase SA
intestinal glands
crypts of Lieberkuhn simple tubular glands that increase the intestinal surface area
invaginations of the mucosa b/w adjacent intestinal villi
absorptive, goblet, Paneth and enteroendocrine cells
microvilli
evaginations of the apical part of the enterocytes to increase surface area
produce a brush border on the apical border of enterocytes
submucosa and muscaris externa
muscularis mucosa - boundary b/w mucosa and submucosa
muscularis externa - responsible for segmentation and peristalis
serosa - thin layer of loose CT covered by visceral peritoneum
segmentation
pattern of annular contraction of smooth m layers which mixes the chyme
peristalsis
contents advance along intestine when proximal contraction is coordinated with relaxation below
microcirculation of SI
intestinal submucosa
villus capillary plexus supplies intestinal villus
pericryptal capillary plexus supplies the lower half of the crypts
lacteals
convey chyle from the intestine to the lymphatic circulating and to the thoracic duct and then to the systemic blood circulation
duodenum
Brunner’s glands
few goblet cells
leaf like villi
jejunum
plicae circulares
irregular villi
more goblet cells
no brunner’s glands and no peyers patches
ileum
many lymphoid nodules (peyer’s patches) in LP and submucosa
finger like villi
most goblet cells
absorptive cells/enterocytes
apical domain w/ brush border
microvilli contain carbohydrate breakdown enzymes
carrier proteins bring carbohydrates into cell
goblet cells
mucus secreting cells throughout enterocytes of intestinal epithelium
secrete glycoproteins
protect against bacterial invasion
paneth cells
secrete antimicrobial proteins to limit bacteria enterocyte contact
kill bacteria directly
protection of SI
goblet cells - gel like blanket tight junctions b/w enterocytes Peyer's patches in epithelium IgA produced by plasma cells Paneth cells - inactivation of microbial cells acidity of gastric juice propulsion
IBD
defect in the protective system accounts for inflammatory bowel diseases
infiltration of neutrophils
inflammation
accumulation of lymphocytes
mucosa of large intestine
lined by simple columnar epithelium formed by enterocytes and abundant goblet cells
enterocytes have short apical microvilli - transport of ions and water
mucosa of colon
straight tubular glands or crypts are characteristic of the mucosa of the colon
enterocytes of LI
simple columnar epithelium
short apical microvilli
effected by aldosterone
goblet cells secrete mucus to lubricate the mucosal surface
glands of Lieberkuhn
contain goblet cells, enteroendocrine cells, and stem cells
NO paneth cells
taenia coli
fused bundles of the outer smooth m layer
contraction produce haustra
