Digestive system overview Flashcards
muscosal protective system
MALT (mucosal associated lymphoid tissue)
regulation and coordination of digestion
via enteric neurons (intrinsic autonomic neurons) and hormones produced by endocrine cells in the mucosal epithelium
Role of coordinated effort of sympathetic/parasympathetic inputs
coordination of peristalsis, effects on blood vessels and glands
Layers of the digestive system, from lumen to mesentary
mucosa, submucosa, muscularis externa, serosa/adventitia
mucosa
epithelial layer, well-vascularized lamina propria (contains lymphocytes, plasma cells, macrophages), muscularis mucosae (smooth muscle)
submucosa
more dense connective tissue than muscosa, larger blood vessels, nerve plexi, glands, lymph nodes
muscularis externa
inner circularly and outer longitudinally arranged layers of smooth muscle and nerve plexes.
peristalsis and churning of lumen contents
serosa/adventitia
covering of squamous epithelial cells
esophagus
non-cornified squamous epithalium.
upper = skeletal muscle under voluntary control
midway = mix of skeletal/smooth muscle
lower 1/3 = smooth muscle
small, incomplete sphincter c maintained muscular contraction –| reflux
lacks thick mucous covering –> burning sensation on reflux, ulceration
3 histological regions of the stomach
cardia, fundus, pyloris
cardia
small area of mucus-secreting glands around the entry of the esophagus
fundus
main body of the stomach
secretes acid, peptic digestive products and mucus
pyloris
secretes mucus
endocrine cells –> gastrin
muscularis externa of the stomach
circular, longitudinal, and OBLIQUE layers
gastric pits
spaces between epithelial folds of the gastric epithelium
gastric glands
at bottom of mucus-secreting gastric pits
differentiated epithelial cells –> digestion of food at acidic pH
How often are surface cells of the gastric epithelium replaced?
every 3-5 days
rate of turnover for differentiated cells deep in the gastric glands
6-12 mo
location of gastric stem cells
upper neck region of gastric pit –> upward as mucus secreting cells, downward as gastric gland cells
surface mucous cells
secrete mucin and bicarbonate –> viscous protective layer
covered by glycocalyx (layer of glycoproteins)
chief cells
secrete pepsinogen
acid converts to pepsin (protease)
multiply through division or stem cells
parietal cells
pump H+ ions via H/K ATPase into lumen of the gastric glands –> pH of 1 - 1.5
energy-demanding –> increased mitochondria
secrete intrinsic factor –> B12 uptake
gastrin and histamine
stimulate acid secretion by parietal cells
excessive secretion of gastrin –> overproduction of HCl by parietal cells –> duodenal ulcers (increased acid cannot be neutralized)
Zollinger-Ellison syndrome