9.2 Ingestion and digestion Flashcards
What stimulates thirst?
what stimulates hunger?
What stimulates saity?
Thirst: ADH/aldosterone
Hunger: glucagon and ghrelin
Satiety: Leptin and cholecystokinin
What type of muscle is the esophagus made out of?
Top third: skeletal muscle
Bottom third: smooth muscle
Middle: both
Where does the digestion of fats and carbohydrates start?
Carbohydrates & Fats: mouth
What do the glands of the stomach respond to?
What nerve innervates it?
Gastric glands respond to signals from the vagus nerve.
What are the six things that the stomach secretes?
- HCl
- Pepsinogen- cleaved to make pepsin, which partially digests prtoeins
- Mucus (protects mucosa
- Bicarbonate- protect mucosa
- Water- dissolves and dilutes ingested material
- Intrinsic Factor- required to absorbed b12
What are chief cells and pareital cells and what do they secrete?
Chief Cells- pepsinogen
Parietal Cells- Hydrogen ions, cleave pepsinogen to pepsin.
This is unique because most enzymes are only active at a normal human pH
What do pyloric glands contain and what do they secrete?
Pyloric Glands- contain g- cells that secrete gastrin.
this induces the parietal cells in the stomach to secrete more HCl and signals the stomach to contract, mixing its contents.
What is chyme?
acidic, semifluid mixture made in the stomach from food contents.
What does chyme do in the duodenum?
It causes the release of brush boarder enzymes such as
-disaccharidases (maltase, isomaltase, lactase, and sucrase)
and peptidases.
Why do people with lactase deficiency have diarrhea.
In general, lactase is able to break down lactose, and then the bacteria in the intestines are able to hydrolyze that disaccharide, producing methane gas.
However, undigested disaccharides have an osmotic effect. So water is pulled into the colon, resulting in diarrhea.
What is aminopeptidase?
What are dipeptidases?
Aminopeptidase: is a peptidase secreted by glands in the duodenum that remove the N-terminal amino acid from a peptide.
Dipeptidases cleave the peptide bonds of dipeptides to release free amino acids.
What does enteropeptidsase do?
It is an enzyme critical for the activation of trypsinogen to trypsin, a pancreatic protease
They can also activate procarboxypeptidases A and B to their active forms.
What is secretin?
It is a peptide hormone that causes pancreatic enzymes to be released into the duodenum.
It regulates pH of the digestive tract by reducing HCl secretion from parietal cells and increasing bicarbonate secretion from the pancreas.
It is also an enterogastrone, a hormone that slows mobility through the digestive tract. This allows increased time for digestive enzymes to act on chyme, especially fats.
What is cholecystokinin?
It is secreted in response to the entry of chyme into the duodenum.
It stimulates the release of both bile and pancreatic juices and also acts on the brain, where it promotes satiety.
What is bile?
It is a complex fluid composed of bile salts, pigments, and cholesterol.
They are not enzymes, and do not directly perform chemical digestion (i.e. breaking of chemical bonds).
However, they do help in mechanical digestion and facilitate the chemical digestion of lipids.
It emulsifies fats and cholesterol into micelles, increasing the surface area and therefore increasing the rate at which lipase can act.
