6. Digestive System Flashcards
Role of Mouth
mastication (mechanical breakdown)
Role of Pancreas
creates digestive enzymes
Role of Small Intestine
absorbs nutrients (95% of absorption)
Role of Duodenum
mixes the chime with pancreatic enzymes
Role of Colon
reabsorbs minerals and water into the blood
Role of Rectum
gets rid of waste
What are villi and microvilli?
- Villi are made up of microvilli
- They line the small intestine and absorb nutrients
What are the enzymes in saliva, and what do they break down?
- Amylase and Lipase
- they break down food into smaller molecules to make them more easily absorbed
What are the major cell types in the stomach, and what do they do? (4)
- Mucus Neck Cells: produce mucus that prevents the stomach from digesting itself
- Pariental Cells: produce HCl to adjust pH of the stomach
- Chief Cells - produce Pepsin which degrades food proteins
- Enteroendocrine Cells: initiate digestive actions
What is Peristalisis? What causes? What is it’s function
- it’s a muscle contraction which causes a wave down a muscular tube
- it propels food and chyme through the digestive tract
- it’s caused by a wave contraction followed by a wave relaxation
How does digestion occur in the stomach, and what is digested?
- Peristalsis occurs allowing the food to mix with pepsin and HCl
- PROTEINS ARE DIGESTED and chyme is created
What are the 3 parts of the small intestine? Describe digestion/absorption of each
- Duodenum: mixes chyme with pancreatic enzymes
- Jejunum: absorbs nutrients that were broken down by the pancreatic enzymes in the duodenum
- Ileum - absorbs anything not absorbed by the jejunum
What enzymes are produced in the Pancreas, and how are they activated?
- the pancreas produces chymotrypsinogen, bicarbonate, lipase/amylase, and trypsinogen
- they’re activated by proteolytic cleavage
What is the function of bile salts, and where do they come from?
- they act as emulsifiers to lower cholesterol by emulsifying lipids
- they come from the liver
What’s the difference between the endocrine and exocrine (digestive) parts of the pancreas?
- Endocrine secretes hormones into the internal environment; doesn’t have ducts
- Exocrine secretes sweat, oils, and wax into the external environment; has ducts
What are the major cell types in the pancreas, and what do they do?
Centroacinar Cells (exocrine) - secrete bicarbonate
Acinar Cells - secrete digestive enzymes
What are the major parts of the colon, and what happens in each part?
- Ascending colon (reabsorbs water and electrolytes)
- Transverse colon (more reabsorbtion of water and electrolytes)
- Descending colon (storage depot for feces)
- Sigmoid colon (moves stool into the rectum)
What are the major hormones involved in digestion? (5)
Gastrin; Secretin; Cholecystokinin; GIP; Motilin
Gastrin
- hormone from the stomach
- stimulates HCl secretion
Secretin
- hormone from the duodenum
- signals secretion of sodium bicarbonate which stimulates bile secretion
Cholecystokinin (CCK)
- hormone from the duodenum
- stimulates the release of bile and pancreatic enzymes
Gastric Inhibitory Peptide (GIP)
- hormone from the duodenum
- induces insulin secretion
- slows rate of stomach emptying by inhibiting mixing and churning
Motilin
- hormone from the duodenum
- stimulates production of pepsin
How do insulin and glucagon differ in function?
- insulin: responds to high blood sugar
- glucagon: responds to low blood sugar
