Gastrointestinal Review Flashcards
Describe the functions of the GI tract
Digestion
absorption
Excretion
endocrine
Describe the mouths function
Mastication along with salivary amylase assists in breakdown of CARBS and STARCHES into maltose
Describe the stomach cells
Mucosal (neck) - secretes mucus and gastrin, G cells produce gastrin which stimulates gastric secretions
Chief Cells - produce pepsinogen, HCL activates pepsinogen to active form pepsin (aids in protein digestion)
Parietal - secretes HCL and intrnisic factor, HCL destroys many bacteria, intrinsic factor is necessary for absorption of Vit B12 in terminal
Mast - secrete histamine
Describe the function of chyme in the SI
Presences stimulates the release of secretin from S-cells found in the duodenum
Secretin stimulates pancreatic acinar cells to release bicarbonate and water and decreases gastric activity
Bicarbonate-rich mucus is also secreted by Brunner’s glands neutralizing the gastric acid and makes the pH alkaline
Describe CCK
Stimulated by fat in the duodenum
released by I-cells
causes sphincter of Oddi to relax
causing bile to be excreted into duodenum
Also stims the pancreas to secrete enzymes which aid in of fat, starches, and protein
Pancreatic amylase completes breakdown of maltose
Describe the breakdown of sugars in the SI
Maltase —> maltose —> two molecules of glucose
Lactase –> lactose —> glucose and galactose
Sucrase –> sucrose –> glucose and fructose
Describe the exocrine function of the pancreas
Makes up the bulk of the pancreas
Tyrpisogen is activated by enterokinase into trypsin
Pancreatic amylase aids in digestion of starch to produce maltose
Lipase breaks downs fat into fatty acids and glycerol
Describe the endocrine function of the pancreas
Glucagon (alpha =20%)
Insulin (beta = 70% of islet cells)
Somatostatin (delta =10%)
Describe the large intestine
Absorbs most of the water
Bacteria found in LI produce vitamin K
Contains numerous goblet cells that secrete mucus
Describe vitamin and mineral absorption
Fat soluble: DAKE
Water soluble: B, C and folic acid (B12 exception) enter enterocytes by secondary active transport mechanisms using Na - amino acid co-transporters
Folic acid and Iron are absorbed in the Jejunum:
- Iron combines with apotransferrin in the blood to form transferrin
- transferiin carries the iron in the blood to cells in the live,r spleen, and bone marro
- iron is then bound to apoferritin to form ferritin
What is the role of the liver
Carb metabolism: glycogenesis, glycogenolysis, gluconeogenesis
Protein metabolism
Lipid metabolism
Stores: glycogen and vitamins A, D, and B12
Detoxes
Conjugates bilirubin
Makes steroids. clotting factors
Makes RBC in fetuses
involved in immunity through Kupffer cells
Describe bilirubin
Byproduct of RBC breakdown in the spleen
RBC > 120 days broken down into heme and globin
Describe the role of the gallbladder
Stores (50cc) and concentrates bile
Excretes bile in response to fat in the duodenum
Stimulated by CCK
Describe gastrin
G cells
Stimulates HCL secretion from parietal cells
stimulates gastric motility
Describe somatostatin
D cells in stomach and delta islet cells in pancreas
decreases pancreatic secretion
