Digestion and absorption Flashcards
The digestive process essentially breaks down large macromolecules into molecules small enough to be absorbed across intestinal epithelial cells. Chemical and mechanical digestion begins in the mouth and continues in the stomach. Chemical digestion completes this process within the small intestine
The duodenum receives secretions from accessory organs - what are these
Exocrine pancreas
Liver
Gall Bladder
what does the exocrine pancreas secret - 4 things
Digestive enzymes such as pancreatic amylase ( target carbs) , trypsin ( proteins) , pancreatic lipase ( targets fats) and phospholipase A2 - these digest macromolecules down into smaller components that can be further digested by brush border enzymes into monosaccharides and aa.
Bicarbonate - to neutralise gastric acid entering from stomach
water and mucus
what things create a neutral pH for pancreatic enzymes to work
bicarbonate
water
mucus
what is the role of bicarbonate secretion from the exocrine pancreas
neutralises gastric acid entering from the stomach
what synthesis bile
liver
bile compromised of bile salts, phospholipids, cholesterol , bile pigments such as bilirubin and bicarbonate
where is bile stored
gall bladder
what does amphipathic mean
having both water-soluble and fat-soluble sides
emulsification and formation of micelles
bile salts emulsify lipid globules into smaller droplets to allow pancreatic lipase (and other lipid digesting enzymes) to gain access to fat molecules and digest them to monoglycerides, free fatty acids, free cholesterol (derived from cholesterol ester) and lysolecithin (derived from phospholipids). Bile salts and phospholipids are also components of micelles that transport digested fat molecules through the aqueous environment of the intestinal lumen to the surface of microvilli for absorption into intestinal epithelial cells.
The precipitation of bile into crystalline material within the gall bladder can result in the formation of what
gall stones - potential to block bile duct
surgical removal - before surgery advised to eat little
what dietary advice would you offer to a patient who has had their gall bladder removed.
bile is involved in aiding the digestion of fat- would think advice would be to reduce that.
With removal of gall bladder via cholescystectomy, bile no longer stored in gall bladder pior to release from common biel duct into the duodenum - liver to intestine direct
so has minimal impact on digestion.
where does the bile duct run
series of thin tubes that go from liver to small intestine. Main job is to allow fluid called bile to go from liver and gallbladder to small intestine. Begins in liver as many tubules called ductules , then ducts and then merge into left and right hepatic ducts. In the liver called the intrahepatic duct.
Gallbladder is joined to common hepatic duct by small duct called the cystic duct. Combined duct is called common bile duct. Enters the duodenum at the ampulla of water
where does the common bile duct enter the duodenum
ampulla of vater
Disaccharides formed by action of secreted enzymes are digested by equivalent brush border enzymes e.g. lactase breaks down lactose into glucose and glaactose and sucrase isomaltase breaks down sucrose into glucose and fructose
how are they all transported through on the basal side
passive facilitated transport through GLUT-2
on luminal side glucose goes through sodium glucose transporter - SGLT - secondary active transport using sodium symporter
fructose goes GLUT 5 passive
small peptides are digested by trypsin and carboxypeptidases A and B to form amino acids as well as intestinal epithelial cells via amino peptidases - how are they transported across luminal and basal epithelial cell membranes
luminal - active transport using sodium and hydrogen symporters
basal - aa exit via various passive carriers
triglycerides are digested bu pancreatic lipase amongst others forming monoglycerides , free fatty acids and cholesterol and cross luminal membrane via passive diffusion how do they move across basal membrane
re-esterfied into triglycerides and packaged into chyloamicrons which leave the cell by exocytosis and enter into lymphatic lacteals
symptoms of lactose intolerance
bloating , diarrhoea and flatulence - mostly Asians. Lactose is not digested in small used by bacteria in large Intestine causing production of CO2 so flatuelnce and exerts osmotic effect drawing in water from surrounding ECF leading to colonic oedema so belatedness and diarrhoea.
