GI secretion, digestion and absorption

Question 1

salivery gland: stimuli

Answer 1

internal stimuli: change in stomach (instrintic; short reflex)
external stimuli: sight smell
(extrinstic; long reflex)

Question 2

salivery gland

Answer 2

parasympathetic: watery, enzyme-rich saliva
sympathetic: thick, mucous-rich saliva

Question 3

gland cell

Answer 3

mucous neck cell: mucus
parietal: secrete HCl and intrinsic factor (glycoprotein)
chief cells: produce pepsinogen (pepsin) and lipase
enteroendocrine cells:
gastrin=increase HCl
somatostatin=decrease HCl

Question 4

mucosal barrier

Answer 4

mucous cells are joined tgt by tight junction
(prevent gastric juice leak into the tissue layer)

Question 5

secretory functions

Answer 5

HCl: kills pathogen; activate pepsin from pepsinogen
pepsinogen: activated by HCl to pepsin (proteinase)
instrinsic factor: glycoprotein: bind and promote synthesis of B12 (synthesis of RBC)
deficiency of glycoprotein: pernicious anaemia
molecular that stimulate HCl: gastrin, histamine and acetylcholine

Question 6

inhibitary events of gastric juice

Answer 6

cephalic phase: loss of appetite -> cerebral cortex -> decreased parasympathetic activity
gastric phase: excessive acidity in stomach -> G cells -> decreased gastrin release to blood ; emotional stress -> sympathetic nervous system activation
intestinal phase: distention of duodenum -> enterogastric reflex

Question 7

stimulatory events of gastric juice

Answer 7

cephalic phase: external stimuli -> cerebral reflex -> hypothalamus and medulla oblongata -> vagus nerve
gastric phase: stomach distention -> long reflex (parasympathetic) ; rising pH -> G cell activation -> gastrin release in blood
intestinal phase: presence of partially digested food in duodenum -> intestinal gastrin release to blood

Question 8

HCl secretion

Answer 8

in parietal cell:
histamine, acetylcholine, gastrin receptor
activation of H+K+ ATPase

Question 9

Liver

Answer 9

secrete bile: leave liver through hepatic duct
stellate macrophage: remove bacteria, worn-out blood cell

Question 10

gallbaldder

Answer 10

store and concentrate bile
bile salt: emulsify fat
recycled through enterohepatic circulation
bilirubin: break down product of RBC

Question 11

carb digestion

Answer 11

absorption:
glucose/ galatose -> Na - cotransport
frutose -> facilitated diffusion

Question 12

protein digestion

Answer 12

absorption:
amino acids -> Na+ co-transport
di/tripeptides -> H+ co-transport

Question 13

fat digestion

Answer 13

michelle formation: bile salt + fatty acids + monoglycerides
micelle enter enterocytes: reform into chylomicron