Module 3 - GI tract Flashcards
what is salivary secretion composed of ?
- mucus - for lubrication
- Dilute solution of NaCl
- allows to dilute food
- this allows optimal ph to be reached for digestive enzymes - Digestive enzymes
- Lingual lipase
- a - amylase
what are the functions of the salivary secretion ?
- Aids in talking and chewing and swallowing food
- Hygiene
- Digestion
- dissolves food allows taste
- lingual lipase - fats
- a amylase - starch
- lingual lipase - fats
- dissolves food allows taste
how is salivary secretion regulated ?
through nervous and autonomic nervous system
Nervous
- thought, smell, sight of food
- presence of food in mouth
Autonomic
- para
- stimulates secretion of a lot of fluid
- Sym
- small volumes of viscous fluid
composition of gastric secretion?
- mucous cells
- chief cels -pepsinogen
- parietal cells - intrinsic factors
what are the functions of gastric secretion?
- the mucus protects against abrasion and acid
- Intrinsic factor
- absorptive of vitamin b12 - Pepsinogen
starts the digestion of proteins
- is converted into the active form of pepsin by acid - Gastric acid
- dilutes food
- denatures proteins
- activates pepsinogen
secretion of hcl
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how is gastric secretion regulated ?
this is coordinated with eating and arrival of food
- divided into 3 phases
what are 3 phases through which gastric secretion is regulated
- Cephalic phase
- Gastric phase
- Intestinal phase
explain the cephalic phase?
20% of secretion associated with this phase
- this phase is where the body prepares for the arrival of the good
Stimuli
-the sight of food, the thought of food
Parasympathetic nervous system
- via the enteric nervous system it stimulates
- chief cells
- goblet cells
- parietal cells
it also stimulates the secretion of hormone gastrin which is released into the blood and this hormone also stimulates parietal and chief cells
explain the gastric phase?
70% of secretion is associated with this phase
This phase ensures that their is sufficient to handle ingested food
Stimuli in stomach
- stretch of stomach wall
- elevated ph
Nervous and hormonal regulation
local nervous reflex
- enteric nervous system
external nervous reflex
- parasympathetic system
stimulates
- secretion
- gastrin secretion
- motility
explain the intestinal phase ?
10% secretion
stimuli
- stretch of the duodenum
- the arrival of acid chyme, lipids and carbohydrates
Nervous and hormonal regulation
Hormones
- CCK, GIP, secretin
Nerves
- enterogastric reflex
Both inhibit secretion and motility
what is the composition of pancreatic secretion?
consists of
- enzymes - acinar cells and chemical digestion of food
- Alkaline fluid
- duct cells
- neutralises acid
- optimum ph for enzymes
what is function of pancreatic enzymes?
luminal chemical digestion of food
how is pancreatic secretion of enzymes stimulated ?
- secretion of digestive enzymes is by acinar cells which is stimulated by hormone CCK
how is the secretion of alkaline fluid stimualted?
by hormone secretion, secretion of secretin stimulated by arrival of acid chyme in duodenum
what are products associated with digestion in biliary secretion?
- bile salts
- HC03-
what are the excretory products in biliary secretion?
bile pigment- waste products
cholestrol
what is the function of biliary secretion?
bile salts - fat digestion
HC03- - neutralises acid
bile pigments - excretion
how is biliary secretion regulated ?
- bile is secreted in the liver, it is delivered to the duodenum when the food arrives
- the initial delivery of bile is under hormonal control
- CCK
Bile stimulates its won secretion
- enterohepatic circulation
what does the CCK hormone do ?
- it is produced in response to products of digestion in duoder
- contraction of gall bladder
- relaxation of hepatopancreatic ampulla
what is enterohepatic circulation
it is the process of reabsorbing 95% of the bile in the ileum
what does the SI consist of and what do the components do?
- mucus for lubrication
- isosmotic fluid
- alkaline - HELPS TO neutralise acid and dilutes food to aid digestion
digestive enzymes
- shed cells
name the major nutrients in our food
- carbohydrates
- proteins
- fats
what 2 monosaccharide is sucrose made out of ?
glucose and fructose
what 2 monosaccharide is lactose made out of ?
glucose and galactose
what 2 monosaccharide is maltose made out of ?
glucose and glucose
what are sources of protein?
- 50% from the diet
- 50% endogenous proteins
what are digestive enzymes?
- are extracellular
- are organic catalysts
- need different enzymes for different substrates
- have different optimal ph’s
- salivary enzymes - alkaline
- gastric enzymes - acidic
- small intestinal - alkaline
