Digestion 8 Flashcards
How are pancreatic lipases made? How do they opperate?
Trypsin will activate colipase (from pro-colipase in the pancreas) which will activate the pancreatic lipase
Lipase is going to take triglyceride and break it down into fatty-acids, di and mono glycerides
How much bile is secreted per day?
0.5-1 liter per day
What ions are in the pancreatic bile and what type of solution is it? What is the pH
Na
K
Cl
HCO3
Isotonic
7.8 - 8.2 to neutralise the chyme
What solids are in the bile? (3%)
NO ENZYMES
Bile acids (salts)
Bile pigment
Cholesterol
Phospholipids
Bile secretion by the liver is _______
Entrance of bile into the duodenum is ________ (about _____ per day)
It is stored in the _________ when the ___________ is closed.
continuous
Intermittent. (500-700 ml/day)
gallbladder
sphincter of Oddi
Bile salts are synthesized in the ______ from________
What are the functions of bile salts?
Liver
Cholesterol
Facilitate digestion, transport and absorption of fats by forming water-soluble complexes with the fats
How can the gallbladder deal with the large amounts of bile given its small size? What happens following that action?
It concentrates the bile more (3% to 10-20%)
and so increases the viscosity and slightly lowers the pH
If someone needs a Cholecystectomy because of gallstones (from cholesterol and pigment), what happens to the bile secretion?
The bile will be less concentrated and will not breakdown fatty meals as efficiently
How does forming water-soluble complexes with fats help with digestion, transport and absorption of fats?
The emulsion allows for less surface to cover per lipase and keeps them in a more digestible size
The body synthesises about 0.5 g of bile salts but releases about 15-20 g into the intestine daily. how can that be explained?
Most bile is reabsorbed into the portal blood and returned to the liver via the Entrohepatic circulation
The entire bile salts pool is recirculated several times a day
What is the role of bile salts in HEPATIC BILE FLOW?
What happens if bile secretion is removed from the ilium?
- Positive feedback loop: The more bile salts are returned in the portal blood, the larger the volume of bile salts secreted
-The flow will be decreased
What is the role of bile salts in BILE SALTS SYNTHESIS?
What happens if bile secretion is removed from the ilium?
- Negative feedback loop: The more bile is returned to the portal blood, the smaller the amount of new bile salts synthesized
- There will be more synthesis
What is the role of bile salts in THE LIVER?
the solubility of cholesterol is higher in bile and avoids precipitation.
What is the role of bile salts in THE INTESTINE?
They act as detergents and help form stable emulsions of fats so lipase can act on them (as well as fat-soluble vitamins)
What is the role of bile salts in THE COLON?
What will be the effects of too much or too little?
They inhibit Na and H2O absorption
Too much: constipation
Too little: Diarrhea
What hormones can regulate Bile flow? how?
Choleretics: causes the liver to secrete large volumes of bile (secretin)
Cholagogues: causes an increase in gall bladder emptying (CCK)
The pancreas has two types of cells, how are they different?
- releases large volume rich in HCO3 (high pH)
- releases small volume rich in enzymes (low pH)
SUMMARY: Where and by what are carbohydrates, proteins and fats digested?
Carbohydrates: in mouth and intestine by salivary and pancreatic lipases
Proteins: In the intestines by trypsin, pepsin and other amylases
Fats: in intestine by lipase, co-lipase and bile salts
How is surface area increased for absorption?
Villi out pushing into intestine as well as enterocytes that have microvilli on them
What is secreted by crypt cells (invagination) in the intestine to neutralize the chyme?
a large volume of alkaline fluid called SUCCUS ENTERICUS
What are the functions of villi cells?
Complete digestion and absorb fluids
How do villi cells complete digestion?
They synthesise digestive enzymes which stay in the brush border (not a secretion)
Villi cells are exposed to an acid environment, so they _____
Have frequent cell turnover and apoptosis cells are carried in the intestine during MMC
In the villi, how are fats and carbohydrates absorbed?
Fats: via the lacteals with the help of chylomicrons in the lymphatic system (Lymph flow, 2 ml/min)
Carbohydrates: via the capillaries into venous blood (Postprandial blood flow to intestine, 2 L/min)
What is being absorbed in the colon?
Most is reabsorption
(proteins, water)
What are the features of colic secretions?
Alkaline, isotonic and LOTS of mucin
No enzymes
No absorption of nutrients
A lot of bacterial activity
What are the absorption patterns of
Ion/ Ca
CHO
Proteins, lipids, Na, H2O
Vitamin B12
Bile salts
Throughout the small intestines?
Duodenum: Fe, Ca, CHO, Proteins…. (most)
Jejenum: CHO, proteins… (a bit less)
Ileum: CHO, proteins (same), vitamin B12 and bile salts
How does absorption take place?
Simple diffusion, facilitated diffusion, active transport, but any movement of ions or nutrients will also create some osmosis movements
What limits absorption?
- Inadequate pH for enzyme activation
- Adequate site of absorption
- Adequate transit
- Adequate transporters
How much absorption is done is the SI and colon? how much could be done?
SI: 7L. but also 15L
Colon: 2L. but also 5L
