lecture 25 - secretion Flashcards
what are exocrine secretions
produced by epithelia - move into the lumen
what are endocrine “secretions”
move into the body = meaning they aren’t secreted as such
what are the components and functions of exocrine secretions
mucus = protection + absorption, also aids mechanical digestion
electrolyte solution = dilutes food and provides optimal pH, essential for chemical digestion
digestive enzymes = essential for chemical digestions, aids absorption
how much fluid do salivary glands produce per day
1.5 L
composition of salivary secretion
mucus
dilute solution of NaHCO3/NaCl
digetive enzymes
what do the salivary glands aid with
talking, chewing and swallowing
what are the two forms of salivary gland regulation
nervous = thought, smell and sight
autonomic nervous system = parasympathetic and sympathetic
how much gastric secretions do we produce daily
2-3L
what are the functions of intrinsic factor in gastric secretions
stabilises vitamin B12 and facilitates its absorption in small intestine
what are the functions of pepsinogen in the gastric secretions
inactive form of pepsin (converted by acid) that starts digesting proteins
what is the function of gastric acid in gastric secretions
- dilutes food
- denatures protein
- activates pepsinogen to pepsin
- creates optimum pH for pepsin action
- protection
what are the three phases of gastric secretions and what controls them
- cephalic phase = head controls secretion
- gastric phase = stomach controls secretion
- intestinal phase = intestine controls secretion
what is happening the cephalic phase of gastric secretion
preparation of arrival of food
what is the stimuli of the cephalic phase of gastric secretion
- higher centres (CNS) = thought, smell and sight of food
- chewing action, taste
what happens in response to stimuli of the cephalic phase of gastric secretions
extrinsic parasympathetic nervous system response
- stimulates parietal cells, chief cells and goblet cells
- stimulate secretion of hormone gastrin
what is happening the gastric phase of gastric secretion
ensures sufficient secretion to handle ingested food
what is the stimuli in stomach of the gastric phase of gastric secretion
- stretch of stomach wall
- products of digestion stomach lumen
- elevated pH
what happens in response to stimuli of the gastric phase of gastric secretions
- local nervous reflex = enteric nervous system
- external (long) nervous reflex = parasympathetic nervous system
both stimulate secretion from gastric glands and motility
what is happening the intestinal phase of gastric secretion
controls delivery to small intestine
what is the stimuli of the intestinal phase of gastric secretion
- distension of duodenum
- arrival of acid chyme, lipids and carbohydrates into the duodenum
what happens in response to stimuli of the intestinal phase of gastric secretions
- hormones = GIP, CCK, secretin (responding to nutrients +acid, increase enzymes that respond)
- nerves = enterogastric reflex (long reflex duodenum to brain to stomach)
both inhibit secretion and motility
what are the two components of pancreatic secretions
enzymes = acinar cells, chemical digestion of food
alkaline fluid = duct cells, neutralize acid
what do pancreatic enzymes act on
all classes of foods
what are proteolytic enzymes
secreted as inactive precursors and activated to active enzyme in the duodenum
what are the functions of biliary secretions
- bile salts = fat digestion
- HCO3 rich fluid = neutralizes acid
- bile pigments = excretion
what does the hormone cholecystokinin (CCK) do and when is it produced
produced in response to products of digestion in duodenum
- contraction of gallbladder
- relaxation of hepatopancreatic ampulla
