Gut L3 Flashcards
how much water is taken into the body per day
2L
HOW MUCH SALIVA IS FORMED IN A DAY
1.5L
HOW MUCH GASTRIC ACID IS FORMED PER DAY
1.5L
how much pancreatic juices are formed per day
1.5L
how much bile is formed per day
0.5L
how much intestinal secretions is formed per day
1.5L
how much water is absorbed by the colon per day
0.4L
how much water is absorbed by the s.int per day
8.5L
how much water is excreted per day
0.1L
what happens in the cephalic phase
when is it initiated
what is the purpose
give an example
- initiated when receptors in the head (cephalic) are stimulated by though, sight, smell and taste of food
- involves PARASYMPATHETIC NS (preganglionic fibres in vagus nerve)
- prepares body for the influx of food
- stimulates SALIVA, GASTRIC ACID production
- causes GALLBLADDER contraction
- secretion of INSULIN
- eg Pavlovs dogs
what is the importance of the cephalic phase
feed forward mechanism
saliva contains what?
saliva production is triggered by what
what are the 2 phases of
- mucus, enzymes, lipase and amylase
- CONDITIONED reflex, triggered by the PARASYMPATHETIC NS
- BUCCAL/oesophagal phase: food in mouth and swallowing
- GASTRIC phase: irritating food in stomach causing excess salivation and nausea and vomiting
what are the 3 glands that produce saliva and what % of saliva do they produce
SUBMANDIBULAR gland-70%
PARTOID gland- 20%
SUBLINGUAL gland- 5%
acid is released from what
- from PARIETAL cells
- stim by :
- Ach
- local HISTAMINE production
- circulating GASTRIN (hormone) from G cells
amount of acid produced is proportional to what
the amount of ligands that bind
what is the mechanism for HCl secretion
H+ and Cl- separately secreted
- H+ secreted by proton pump
how can gastric acid secretion be dec
1) proton pump inhibitor (O protons can’t enter lumen)
2) histamine receptor drug (removes Histamine as a stimulus for producing HCl, less effective)
para NS connects with whar
submucosal plexus
what is phase 2
gastric phase
once food is eaten
what happens in the gastric phase
- long (3-4 hours)
- stim by: distension in somach, chemoreceptors detect pH changes
- secretion of HCl, pepsinogen, intrinsic factor
- production of MUCUS-BICARBONATE layer (protect stomach from acid)
gastritis is what?
what is it a risk factor for
- inflammation of the lining of the stomach
- inc risk of cancer
what is the role of the bicarbonate in the stomach
- acts as a buffer, titrate protons that get too close to the mucus layer H+ + HCO3—> H2CO3–> CO2 + H2O
- H2O produced O makes the mucus more fluid
how thick is the mucus layer
what is it composed of
what is release stimulated by
- 2mm thick
- 80% CHO, 20% protein
- release stim by ACh from nerve endings
- rich in bicarbonate
what is the purpose of HCO3- in the mucus layer
what is HCO3- inhibited by
- creates micro env around surface cells to prevent damage
- inhibited ADRRENERGIC INPUT (stress)
what is the role of PROSTAGLANDINS in the mucus layer
what happens if you inhibit the nezzymes that make prostaglandins
- cytoprotective
- inc mucus production
- inhibition of enzymes causes GASTRIC DAMAGE (eg NSAIDS)
what happens if TREFOIL proteins on the mucus layer are absent
SIGNIFICANT mucosal damage
what is phase 3
intestinal phase
what happens in phase 3, intestinal phase
- long (hours)
- cholesystokinin released
- gastric inhibitory peptide released
- HCO3- secretions neutralise acidic chyme
- secretion of DIGESTIVE ENZYMES and bile
- pH in stomach drops, O somatostatin released, which is the universal inhibitor
where are the digestive enzymes in the pancreas
Acini clusters which contain Zymogen granules
what is found in pancreatic exocrine secretion
pancreatic juice, watery solution of enzymes and HCO3-
which enzymes are secreted intheir inactive form
whch in active form
PROTEASES = inactive to prevent auto-digenstion
AMYLASE and LIPASES = active
how is bicarbonate secreted from glands
- Cl- ion moves into pancreatic cell, at the same time HCO3- leaves cell
- Cl- leaks back into lumen futile cycle) via CFTR (cystic fibrosis transmemb receptor)
what causes the problems associated with CF
- malfunctioning CFTR channel O futile cycle is lost
- can no longer secrete BICARBONATE
- important for NEUTRALISATION of gastric acid, enzymes being released at th appt pH and not enough FLUIDITY of mucus due to inability to titrate H+ to form H2O
what is bile
a yellow/green alkaline solution cont bile salts, blue pigments (bilirubin/biliverdin), cholesterol, neutral fats, phospholipids and electrolytes
what is the role of bile
to emulsify dietary fat
what are the 2 components of bile
primary bile salts
bile fuild
what is in primary bile salts
what is the structure
- cholic acid, chenodeoxycholic acid
- conjugated w/ GLYCINE or TAURINE and secreted as Na+ salts
- more soluble in this form
what is bile fluid
what does it cont
watery secretion cont HCO3- from the epi cells lining the bile canaliculi
where ae bile salts released
into s.i
where is 95% of bile reabs
ileum
how do bile salts return to liver
portal vein, taken up by HEPATOCYTES and resecreted
how many times per day is the bile salt pool recycled
up to 10 times a day
3-8% lost in faeces
how are secondary bile salts formed
by bacteria in intetsines by dehydroxylation of primary bile salts
deoxycholate (from cholic acid) is absorbed from where
and resecreted from where and in what form
absorbed from colon
resecreted by liver as CHOLIC ACID
lithocholate (from chenodeoxycholic acid) is absorbed how
poorly, it is toxic
