Secretions of the intestine, liver, gallbladder and pancreas Flashcards
what are the. primary secretions of the small intestine
intestinal juice (mucus/HCO3-) pancreatic juice (digestive enzymes) bile (bile salts)
what are key endocrine hormones involved
secretin
CKK
GIP
regulate bile and pancreatic secretions
what are the secretory cells of the SI
villi (absorptive enterocytes and mucus secreting goblet cells) intestinal glands (enterocytes secreting isotonic fluid, enteroendocrine cells, panted cells) in duodenum only (Brunner's lands secrete mucus and HCO3-)
Stem cell renewal of epithelial cells
Rapid turnover of epithelial cells every 3-6 days
differentiate and migrate moving to top of villi
Vulnerable to radiation and chemo
Secretions of SI
Intestinal juice – fluid containing electrolytes and water (secretory enterocytes), lysozyme (Paneth cells), mucus (goblet cells), alkaline mucus containing fluid (submucosal duodenal Brunner’s glands)
Key endocrine hormone secretion (by enteroendocrine cells) into vasculature
CCK (I cells) – stimulate pancreatic and gallbladder secretion
Secretin (S cells) 0 stimulate pancreatic and biliary bicarbonate secretion
GIP (K cells) – may inhibit acid secretion/stimulate insulin release
Exocrine/pancreatic juice
bicarbonate/digestive enzymes
Bile
bile salts for lipid emulsification (liver hepatocyte synthesis, gall bladder storage)
The pancreas’ secretions
Exocrine pancreas secretes pancreatic juice containing bicarbonate rich secretion (pH 8) and digestive enzymes essential for normal digestion and absorption
Pancreatic structure
Clusters of glandular epithelial clusters
99% exocrine acinar clusters secreting pancreatic juice (water, electrolytes, sodium bicarbonate, pro-enzymes)
1% endocrine pancreatic islets (islets of Langerhans) of 4 types secreting glucagon (a), insulin (B), somatostatin (delta), pancreatic polypeptide (F cell)
Exocrine acinar clusters
like grapes main duct to interlobular ducts with lobule with acinar acinar cell (cck, ach) enzyme and cl- rich secretion duct cell (secretin) HCO3- rich secretion
Acinar and ductular secretions
acinar enzymes NaCl fluid
ductular NaHCO3 fluid
Regulation of Acinar enzyme production
Ach released via ps vagus stimulation
CCK – trigger is chyme containing fat and protein products
Produces lower volume enzyme rich pancreatic juice
regulation of ductal bicarbonate and water
Secretin – trigger is H+ in highly acidic chyme
Produces copious HCO3- rich low enzyme pancreatic juice
Pancreatic enzymes
Proteolytic enzymes secreted in inactive form, proteins to peptides
Amylase hydrolyses starch, glycogen and other carbs (other than cellulose) to form di and trisaccharides
Lipases hydrolyse fat into fatty acids and monoglycerides
Nucleases digest RNA and DNA to nucleic acids
Trypsin inhibitor prevents activation to trypsin to prevent pancreatic digestion