Lecture 25 GI Physio Secretion Flashcards
what are the Major EXOCRINE secretions?
Enzymes
Mucus
Electrolyte (serous) solution
whats the Functions of exocrine secretion?
Digest food
Dilute food
Optimal pH
Protection and lubrication
exocrine secretions
whats the volume of saliva, stomach, pancreas, liver, and SI? (from least to most)
Liver = 0.5 L / day
Pancreas, Saliva, SI = 1.5 L/day
Stomach = 3L/day
~8L/day + oral intake
RE- absorption important
production of saliva
whats the 3 pairs of salivary glands?
Parotid gland
sublingual gland
submandibular gland
whats the volume and rate of saliva?
1.5 L day-1
Rate
- Basal 0.3 ml/min
- Stimulated - 1.5 ml/min
whats the composition of saliva?
Mucus (lubrication)
Dilution solution of NaHCO3 / NaCl
Enzymes (a-amylase, lipase)
why do you have Dilution solution of NaHCO3 / NaCl in saliva?
dilution
optimal pH
what enzymes in saliva?
a-amylase
lipase
whats the functions of saliva?
Not essential
Lubrication
Hygiene
Digestion
why do you need lubrication from saliva?
chewing
swallowin
why do you need hygiene from saliva?
irrigation
whats digestion from saliva?
dissolves food allows tasting
a-amylase
how do you regulate of salivary secretion?
Nervous
Autonomic nervous system
what does the Nervous do for regulation of salivary secretion?
Thought, smell, sight of food
Presence of food in mouth, chewing
what does the Autonomic nervous system do for regulation of salivary secretions?
Parasympathetic
- Acetylcholine - copious volumes
Sympathetic
- Adrenaline - small volume of viscous fluid
regulation of salivary secretions
Autonomic nervous system
Parasympathetic
Acetylcholine -
copious volumes
regulation of salivary secretions
Autonomic nervous system
Sympathetic
Adrenaline -
small volume of viscous fluid
whats the volume of gastric secretions?
2 - 3 L per day
whats the volume rate of gastric secretions?
- Between meals
- Eating / food in stomach
- Slow rate (15-30 mls/hr)
- Superimposed on basal rate (150 mls/hr)
whats the composition of gastric secretions between meals?
mainly mucus
whats the composition of gastric secretions while eating / food in stomach?
NaCl / H2O Acid 150 mM HCl, pH 1.0 Mucus HCO3 Pepsinogen Intrinsic factor
for gastric secretions
whats the function of mucus?
Protection against Abrasion and Acid
for gastric secretions
whats the function of intrinsic factor?
Absorption of Vitamin B12 in small intestine
for gastric secretions
whats the function of pepsin?
Secreted as pepsinogen
Converted to active form pepsin by acid
Starts digestion of proteins
for gastric secretions
whats the function of Gastric acid?
Denatures protein Activates pepsinogen to pepsin Optimum pH for pepsin Protection Dilutes food
what do surface cells secrete?
mucus / HCO3
what do chief cells in the gland secrete?
pepsinogen
what do parietal cells in the gland secrete?
acid
intrinsic factor
regulation of gastric secretion
whats it coordinated with?
eating and arrival of food
regulation of gastric secretion
what are the 3 phases?
cephalic
gastric
intestinal
whats the cephalic phase?
head controls secretion
~20% of secretion associated with meal
preparation
stimuli
- Higher centres (though, smell, sight)
- chewing action / taste
whats the cephalic phase respond systems?
parasympathetic NS
modifies activity of ENS - stimulates motility and secretion
cephalic phase diagram
sight and of food, and stimulation of taste and smell receptors ⟶ cerebral cortex ⟶ hypothalamus and medulla oblongata ⟶ vagus nerve
whats the cephalic phase stimuli?
- Higher centres (though, smell, sight)
- chewing action / taste
whats the gastric phase?
stomach controls secretion
~70% of secretion associated with a meal
ensures sufficient secretion to handle the ingested food
whats the gastric phase stimuli?
stretch / distension
products of digestion
what does the gastric phase responds to?
local reflex - ENS
external reflex - para NS
what does the local reflex (ENS) and external reflex (para NS) of the gastric phase stimulate?
motility and secretion
whats the intestinal phase?
intestine regulates secretion
~10% of secretion associated with the meal
controls delivery to SI (-‘ve feedback)
whats the intestinal phase stimuli?
distention of duodenum
arrival in duodenum of: Acid and products of digestion
what does the intestinal phase respond to?
Hormones - GIP, CCK and secretin
Nerves - enterogastric reflex
what does Hormones - GIP, CCK and secretin, and Nerves - enterogastric reflex of the intestinal phase do?
Inhibit motility and secretion
what phase inhibits motility and secretion?
Intestinal phase
what phase stimulates motility and secretion?
cephalic - modifies activity of ENS
Gastric - ENS (local reflex) and para NS (ext reflex)
what phase has the most secretion associated with a meal?
gastric = 70 cephalic = 20 intestinal = 10
whats the volume of pancreatic secretions?
1-1.5 L/day
whats the composition of pancreatic secretions?
enzymes = acinar cells
Alkaline fluid (HCO3) = made by ducts
what do acinar cells do?
act on all classes of food
what are some acinar cells enzymes?
for: Lipolytic Amylytic Proteolytic Nucleolytic
lipo = lipase, phospholipase amy = amylase proteolytic = trypsin, chymo, carboxypeptidase nucleolytic = ribonuclease, deoxyribonuclease
whats the function of acinar cells?
Chemically digest food material
Pancreas most important source of digestive enzymes
what is enzyme (of acinar cells) secretion stimulated by?
CHOLECYSTOKININ
CCK
what are proteolytic secreted as?
inactive precursor
proteolytic secreted inactive precursor
whats it for
Trypsin
Chymotrypin
Carboxypeptidase
Trypsinogen
chymotrypsinogen
procarboxypeptidase
what does trypsin do in SI?
activates other enzymes
in SI
how is trypsinogen converted to trypsin?
by enterokinase (enteropetidase) bound to the duodenal membrane
whats Alkaline fluid (HCO3) - ducts?
Neutralises chyme (acidic – from stomach)
Creates optimum pH (6.7 – 9) for pancreatic and intestinal enzymes.
made by duct cells
stimulates secretin
whats secretin?
stimulates HCO3 secretion
what produces isosmotic HCO3 rich solution?
duct cells
Regulation of pancreatic secretion
Slow basal rate during fasting.
what type of regulation occurs during a meal?
Hormonal
Regulation of pancreatic secretion.
what hormones are secreted for Hormonal regulation during meal?
CCK (Cholecystokinin)
Secretin
whats CCK (Cholecystokinin)?
Produced by duodenal endocrine cells in response to digestive products in lumen
- amino acids, fats, carbohydrates
Stimulates enzyme secretion by acinar cells
wheres CCK produced?
by duodenal endocrine cells in response to digestive products in lumen
- amino acids, fats, carbohydrates
what does CCK do?
Stimulates enzyme secretion by acinar cells
whats Secretin?
Produced by duodenal endocrine cells in response to increased [H+] in lumen
Stimulates HCO3 secretion by duct cells
wheres secretin produced?
by duodenal endocrine cells in response to increased [H+] in lumen
what does secretin do>
Stimulates HCO3 secretion by duct cells
whats the volume of biliary secretion?
0.5 L/day
produced in liver
what are the Products associated with digestion in liver / biliary secretion?
Bile salts & lecithin
HCO3 rich fluid - secreted by duct cells
what are the Excretory products in liver / biliary secretion?
Bile pigments - waste products
Cholesterol - excreted by liver
whats the function of bile?
Bile salts and lecithin
- Fat digestion and absorption
HCO3 rich fluid
- Neutralizes acid chyme
Bile pigments
- Excretion
whats the function of Bile salts and lecithin?
Fat digestion and absorption
whats the function of HCO3 rich fluid?
Neutralizes acid chyme
whats the function of Bile pigments?
Excretion
where is bile delivered and what control is it under?
to duodenum when food is present.
Hormonal control
delivery of bile is under hormonal control. what hormone and how?
CCK (cholecystokinin)
products of digestion in duodenum
contraction of gall bladder
Relaxation of duodenal papilla (sphincter of Oddi)
what is the volume of the SI secretion?
1.5 L/day
what does the SI secrete and why?
Mucus
- Lubrication
NaHCO3 solution (+ NaCl)
- Neutralise acid
- Dilute food
what does the LI secrete and why>
Mucus
- lubrication
GI secretion
what are the Major EXOCRINE secretions?
Enzymes
Mucus
Electrolyte (serous) solution
GI secretion
whats the Functions of exocrine secretion?
Digest food
Dilute food
Optimal pH
Protection and lubrication