Phys 65: GI secretion Flashcards
Cells on surface of GI epithelium
Goblet cells AKA mucous cells
Invaginations of epithelium into submucosa aka
Pits
called crypts of lieberkün in intestine
Glandular cell secretions accomplished via
Exocytosis
Daily secretion of saliva amount
800-1500 ml
Average 1000ml
Two major saliva protein secretion types
Serous secretion
Mucous secretion
Salvia serous secretion protein
ptyalin
type of α-amylase
disgests starches
Mucous saliva secretion protein
Mucin
Acts as lubricant
Ions of saliva
Large quantities of HCO3- and K+
Na+/K+ balance in saliva
Na+ is reabsorbed in exchanger for K+
Cl- during saliva production
Reabsorbed passively
Factors in saliva that destroy bacteria
Thiocynate ions
Proteolytic enzymes —> most important is lysozyme
Antibodies
Superior salivatory nucleus CN
VII
Inferior salivatory nucleus CN
CN IX
Esophageal secretion type
Mainly mucous for swallowing lube
Oxyntic glands secrete
Hydrochloric acid, pepsinogen, intrinsic factor, mucus
Pyloric glands secrete
mainly mucus
also some gastrin
Eenterochromaffin like cells secrete
Histamine
Main driving force for hydrochloric acid secretion
H+/K+ ATPase
Basic factors that stimulate gastric secretion
Acetylcholine
Gastrin
Histamine
Intrinsic factor secreted by
Parietal cells
Parietal cell destruction consequences
Achlorohydra (lack of acid)
Pernicious anemia due to B12 deficiency
Type of mucus in stomach
Viscid mucus
What does viscid mucus do
It is alkaline and forms protective layer around stomach
ECL cells are stimulated by
Gastrin
gastrin is secreted by
G cells in pyloric glands
Three phases of gastric secretion
Cephalic
Gastric
Intestinal
Cephalic phase of secretion
Occurs from neurogenic signals due to smell, taste and sight of food.
Originate in amygdala and hypothalmus
Gastric phase of secretion
Due to vagal stimulation from food entering stomach, local enteric reflexes and gastrin mechanism
Gastrin is secreted due to
Protein rich food entering stomach.
Intestinal phase of secretion
Presence of food in duodenum causes small amounts of gastric secretion
Grastric secretion inhibition by
Reverse gastroenteric reflex
Hormones: secretin, GLP-1, somatostatin
Emotional stimuli does what to gastric secretion
increases acid secretion
Pancreatic enzymes for protein digestion
Trypsin
Chemotrypsin
Caboxypolypeptidase
Pancreatic enzymes for fat digestion
Pancreatic lipase
Phospholipase
Cholesteroesterase
Pancreatic proteolytic enzymes are secreted as_____.
Later in the stomach they are ____
inactive forms
Later activated
Activation of proteolytic enzyme mechanism
Trypsinogen is activated to trypsin by enterokinase
Trypsin activates everything else
How is pancreas protected from proteolytic enzymes
Also secretes trypsin inhibitor
When trypsin inhibitor is overwhelmed, pancreas digests itself with its own proteolytic enzymes
Bicarb is secreted into lumen via
Cl-/HCO3- exchanger
Secretion of bicarb stimulated by
Secretin
How is acidic stomach chyme neutralized in instestine
Via bicarb secretion
Cholecystokinin (CCK) function
stimulates pancreatic secretion
Liver bile secretion stimulated by
Secretin
Gall bladder emptying stimulated by
Cholecystokinin
(also weakly vagal)
Sphincter of odi
Keeps bile in gall bladder till its needed
Precursos of bile salts
Cholesterol
Percent of bile salts that are recirculated
94%
Gallstones formed by
Precipitation of cholesterol
Mucous secreting glands in duodenum
Brunners glands
Brunners glands activated by
Tactile stimulation
Vagal stimulation
Secretin
How do enterocytes absorb nutrients
Secrete water, then reabsorb water with digestion products