Flashcards in Nutrition Chapter 4 Deck (36):
What are the steps of the GI tract flow?
1. mouth and salivary glands
7. small intestine
8. large intestine
What role does the mouth and salivary glands play in digestion?
chew food, perceive taste, moisten food
lubricate food with mucus
release amylase enzyme (starch digesting)
initiate swallowing reflex
What role does the esophagus play in digestion?
lubricate with mucus
move food to stomach (peristaltic waves)
What role does the stomach play in digestion?
store, mix, dissolve and continue digestion
dissolve particles with secretions
kill microorganisms with acid
release protein-digesting enzyme (pepsin)
lubricate and protect stomach surface
regulate emptying into small intestine
produce intrinsic factor of B-12 absorption
What role does the pancreas play in digestion?
secrete sodium bicarbonate and enzymes for digesting CHO, PRO, and FAT
What role does the liver play in digestion?
produce bile to aid fat digestion and absorption
What role does the gallbladder play in digestion?
store, concentrate, and later release bile into the small intestine
What role does the small intestine play in digestion?
mix and propel contents
digest and absorb most substances
What role does the large intestine play in digestion?
mix and propel contents
absorb Na, K and H2O
synthesize some vitamins and short-chain fatty acids
What role does the rectum play in digestion?
hold feces and expel via the anus
What are the 4 layers of the wall of the alimentary canal?
1. mucosa - innermost layer, not smooth, has lumen
2. submucosa - blood vessels that carry substances
3. muscle - move food
4. serosa - outermost layer, protects the GI tract
What is amylase?
A digestive enzyme that breaks down starch into simple sugars.
What is lipase?
A digestive enzyme that breaks down fat.
What is gastrin?
A hormone that controls the release of HCl and pepsinogen.
What are the accessory organs?
salivary glands, liver, bile duct, gallbladder, pancreatic duct, pancreas
Where does most digestion occur?
upper part of the small intestine (duodenum)
What are the types of mechanical breakdown?
segmentation (small intestine)
mass movement (large intestine)
crushing into liquid (stomach)
What are the types of chemical breakdown?
digestive enzymes, saliva, gastric juice, pancreatic secretions, bile, intestinal flora
What is saliva?
comes from the salivary glands
lubricates and breaks down CHO (and FAT in infants)
What are the gastric juices?
occur in the stomach
HCl, mucus, pepsinogen, intrinsic factor
What are the functions of the gastric juices?
partially digests protein
destroys salivary amalyase
converts pepsinogen to pepsin
assists in calcium absorption
What are the pancreatic secretions?
sodium bicarbonate (neutralizes stomach acid)
enzymes (proteases, lipases, carbohydrases)
What is bile?
made in the liver, stored in the gallbladder, released in the small intestine
*recycled (enterohepatic circulation)
What is intestinal flora?
occurs in the colon
produces vitamins (K and biotin), metabolizes fiber, produces SCFAs, maintains a healthy colon, prevents colonization of harmful bacteria
Where does most absorption occur?
in the small intestine
What are the 4 types of absorption?
What is the fate of the absorbed nutrients?
They enter either the vascular system or the lymphatic system and are eventually brought to the liver where they are packaged and distributed to cells.
Vascular system nutrients
water soluble and small particles
intestines --> portal vein --> liver
lymphatic system nutrients
fat soluble and large particles
intestines --> thoracic duct --> subclavian vein
enter the bloodstream
What are the hormones associated with digestion?
gastric inhibitory peptide
What is gastrin?
stimulates the secretion of stomach acid and pepsinogen, stimulated by food entering the stomach or thoughts of food
What is CCK?
stimulates gallbladder to release bile, stimulates release of pancreatic enzymes, stimulated by food, presence of fat and protein in duodenum
What is secretin?
stimulates the pancreas to secrete bicarbonate, maintains proper pH in small intestine, stimulated by the presence of acidic chyme and peptones
What is gastric inhibitory peptide (GIP)?
inhibits secretion of stomach acid and enzymes, slows gastric emptying, stimulated by fat and protein in chyme
What are common digestive tract issues?
heartburn, GERD, ulcers, constipation, diverticular disease, diarrhea, vomiting, gas, IBS, IBD