A&P - Chapter 40 (Part 2) Flashcards
What is emptying the stomach after a big meal controlled by? (2)
- Hormonal mechanisms
2. Nervous mechanisms
Hormonal mechanisms
The presence of fat in the duodenum stimulates a hormone that slows down the passage of chyme into the duodenum
Nervous mechanisms
Presence of acid and distention picked up by receptors in duodenal mucosa, then the impulses travel through vagus nerve which inhibits gastric peristalsis
What is included in intestinal motility?
- Peristalsis
2. Segmentation
Segmentation of the intestinal motility (2)
- Occurs in the duodenum and the first part of the jejunum
2. Mixes chyme with digestive juices from the pancreas, liver and intestinal mucosa
Peristalsis of the intestinal motility
Moves chyme through rest of small intestine and into the large intestine
How long does it take for chyme to travel through the length of the small intestines?
5 hours
What is peristalsis regulated by?
- Stretch reflexes
- The hormone cholecystokinin
- CCK
What do chemical changes in digestion result from?
Hydrolysis
Where do digestive enzymes function in?
In the lumen of the digestive tract
Hydrolases
Breakdown food molecules using water
- all digestive enzymes
Are enzymes specific?
Yes
- lock and key
What do enzymes require for optimal function?
- Specific pH
2. Temperature
Do digestive enzymes go in reverse?
No
Why are digestive enzymes continually synthesized?
Because they are continually destroyed or eliminated from body
- even though they are not used up in the reaction they catalyze/assist
What are most digestive enzymes synthesized and secreted as?
Inactive proenzymes
What kind of compound are carbohydrates?
Saccharide
Where do carbohydrates begin to digest?
In the mouth
What enzyme breaks down carbohydrates?
Salivary amylase
Does any digestion of carbohydrates occur in the stomach?
No
Where does most of the digestion of carbohydrates occur?
Small intestines
What are polysaccharides hydrolyzed by? What does it form?
- Amylase
2. Forms disaccharides
What is the final step of carbohydrate digestion?
Going from disaccharides to monosaccharides
What is maltose made up of? (2)
- Glucose
2. Glucose
What is sucrose made up of? (2)
- Glucose
2. Fructose
What is lactose made up of? (2)
- Glucose
2. Galactose
What do proteins break down into?
Amino acids
Where does protein digestion begin?
In the stomach
What are the main proteases of protein digestion? (3)
- Pepsin
- Trypsin and chymotrypsin
- Peptidases
Pepsin
Gastric juice, partially digests proteins
Trypsin and chymotrypsin
Pancreatic enzymes, continue digestion of proteins
Peptidases
Intestinal enzymes, complete digestion of protein to amino acids
