Physiology Flashcards
What are the 4 layers of the GI tract
1- mucosa
2- submucosa
3-muscularis externa
4-adventia/serosa
What layers make up the mucosa of the GI tract
1- epithelium
2- lamina propria
3-muscularis mucosae
where in the body does the submucosa of the GI tract have glands
oesophagus and duodenum
Role of serosa/adventitia
connects organs to surrounding structures
Where in the GI tract is it called adventitia
oesophagus and rectum
Where in the GI tract is it called serosa
stomach, small and large intestine
What is the parasympathetic nerve of the GI tract
vagus nerve
What is the sympathetic nerve of the GI tract
splanchnic nerve
Names of the plexus’ in the GI tract and where they are located
submucosal plexus- between submucosa and circular muscularis
myenteric plexus- between circular muscularis and longitudinal muscularis
name of vitamin B12 deficiency
pernicious anaemia
What is the anti bacterial property of saliva
lysozyme
What kind of glands are saliva glands
exocrine as mouth is outside the body
Which parasympathetic nerves affect salivary secretion
facial and glossopharyngeal
What kind of saliva secretion does parasympathetic cause
very water and lots of it
What kind of saliva secretion does sympathetic cause
small volume of sticky saliva
name of movement in oesophagus
peristalsis
name of folds in the stomach
rugae
main function of fundus of stomach
storage
main function of body of stomach
storage secretion (musuc, HCl, pepsinogen, intrinsic factor)
main function of pyloric region (antrum) of stomach
mixing and grinding
gastrin
what is pepsinogen
inactive form of pepsin enzyme
What stomach cell secrets mucus
mucus neck cell
What stomach cell secrets HCl
parietal cells
What stomach cell secrets intrinsic factor
parietal cells
What stomach cell secrets pepsinogen
chief cells
What enzyme combines CO2 and H2O to form carbonic acid. In which cell does this happen
Carbonic Anhydrase
what molecule directly affects H+ ion secretion into lumen of stomach
Protein kinase
What ion affects protein kinase activity
Ca
What neurotransmitter promotes HCl production
acetylcholine
What hormone promotes HCl production
gastrin
What paracrine hormone promotes HCl production
Histamine
What inhibits cAMP production
prostaglandins
What parasympathetic nerve affects HCl production
vagus nerve
Describe the 2 ways that the vagus nerve promotes HCl production in cephalic phase
Causes ACh to bind to receptor
Stimulates g cells in pylorus region to release gastrin
What is the cephalic phase
pre-emptive response (sight, smell, thought)
During gastric phase, what stimulates vagus nerve
the stomach expanding
During the gastric stage, what causes the stimulation of g cells
peptides in the lumen
What releases histamine in the stomach
ECL cells
What stimulates ECL cells in the gastric phase
ACh and gastrin
What inhibits gastrin activity
low pH (lots of acid)
What 2 things in duodenum inhibit HCl production
acid
fat
carbohydrate
What does acid in the duodenum cause
enterogastric reflex and secretin release which both cause gastrin secretion to decrease and decreases parietal cell sensitivity to gastrin
What does fat or carbohydrate in the duodenum cause
release of GIP which decreases gastrin secretion
What are enterogastrones
hormones released by duodenum in response to acid, fatty acids, monoglycerides and hypertonic solutions
2 main way enterogastrones work
inhibit gastric acid secretion
cause pyloric sphincter to close
What causes pepsinogen to become pepsin
acidic environment (pH<3)
What happens to pepsin in a neutral environment
becomes fully deactivated
Mucus layer has high concentration of what molecule
HCO3 (bicarbonate)
name of gastric content
chyme
what causes increases peristalsis of stomach
gastrin increased contraction
neural control from stomach distention increases contraction
what causes decreases peristalsis of stomach
fat/peptides/carbohydrate/acid/hypertonicity in duodenum
Acid in the duodenum triggers what
vagus nerve and enteric nerves system to stimulate Brunner’s glands
s cells to secrete secretin which stimulate Brunner’s cells
What gland secretes bicarbonate in duodenum and from what layer does this gland come from
Brunner’s gland
submucosa
What does the hormone secretin affect
Brunner’s glands (HCO3)
Pancreas (HCO3)
Liver(HCO3)
What inhibits secretin
neutral pH
What part of pancreas is involved in digestion
exocrine
go from smallest to largest in the travel of pancreatic secretions
acinar cells lobules intercalated ducts intralobular ducts interlobular ducts main pancreatic duct common bile duct hepatopancreatic ampulla duodenum
other name for hepatopancreatic ampulla
sphincter of oddi
What cells secrete digestive enzymes in the pancreas
acinar cells
What cells secrete HCO3 in the pancreas
duct cells
Name of inactive digestive enzymes
zymogens
What converts zymogens to their active form
the enzyme trypsin
Where is trypsinogen converted to trypsin
brush border of duodenum
What enzyme converts trypsinogen to trypsin
enterokinase
What stimulates zymogen secretion
cholecystokinin (CCK)
neural control
What causes CCK release
fats and acid in duodenum
what is in a portal triad
Hepatic portal vein
Hepatic duct
Hepatic artery
What is hepatic chord comprised of
hepatocytes
hepatocyte function
bile synthesis
stores nutrients
interconversion of nutrients (turns glucose to peptide or something along those lines)
detoxification
Six components of bile
Bile acids Lecithin cholesterol Bile pigment (bilirubin from red blood cells toxic metals HCO3
What component of bile is not made by hepatocytes
HCO3 is produced by duct cells
What layers does the gall bladder have
mucosa
muscularis
serosa
How does gall bladder concentrate bile
Na is absorbed by gallbladder, which water follows due to osmolarity
What molecule causes relaxation of sphincter of oddi and gallbladder contraction
CCK (due to fat in duodenum)
Difference between crypts and villi of small intestine
villi-absorption
crypts- secretion
segmentation movement
like peristalsis but it goes backwards and forwards
What cells cause segmentation
intestinal basic electrical rhythm (BER)
Sympathetic nerve effect on BER
decrease
Vagus effect on BER
Increase
What causes peristalsis of intestine
Migrating Motility Complex (MMC)
When does MMC occur
when absorption is complete in intestine
Where does MMC happen
Antrum of stomach to distal end of ilium
What causes MMC to stop
food in stomach
What hormone is involved in MMC initiation
motilin
What connects cecum and ilium
ileocolic sphincter
crypts in large intestine mainly contain what cells
goblet cells
Describe defecation reflex in general
you eat a meal
this triggers mass peristalsis of colon all the way to rectum
distention of rectum produced the urge to defecate
Process of defecation
rectum contracts
internal anal sphincter relaxes whilst external contracts
increased peristalsis of colon which increases pressure on external sphincter
voluntary release of faeces
Role of acetate
forms fat
Role of propionate
Transported to liver and undergoes glycogenesis
Role of butyrate
epithelia growth and regeneration
