packet 21

Question 1

20 feet long----1 inch in diameter
Large surface area for majority of absorption
3 parts
duodenum---10 inches
jejunum---8 feet
ileum---12 feet
ends at ileocecal valve

Answer 1

small intestine

Question 2

Histology of the Small Intestine

–Structures that increase surface area

Answer 2

plica circularis
villi
microvilli

Question 3

permanent ½ inch tall folds that contain part of submucosal layer
not found in lower ileum
can not stretch out like rugae in stomach

Answer 3

plica circularis

Question 4

1 Millimeter tall
Core is lamina propria of mucosal layer
Contains vascular capillaries and lacteals(lymphatic capillaries)

Answer 4

villi

Question 5

cell surface feature known as brush border

Answer 5

microvilli

Question 6

Absorption and digestion
Digestive enzymes found at cell surface on microvilli
Digestion occurs at cell surfaces
Significant cell division within intestinal glands produces new cells that move up
Once out of the way—rupturing and releasing their digestive enzymes & proteins

Answer 6

microvilli

Question 7

Submucosal layer has duodenal glands

Answer 7

secrete alkaline mucus

Question 8

Mucosal layer contains intestinal glands = Crypts of Lieberkuhn (deep to surface

Answer 8

secretes intestinal juice
1-2 qt./day—— at pH 7.6
brush border enzymes
paneth cells secrete lysozyme kills bacteria

Question 9

Mouth—salivary amylase
Esophagus & stomach—nothing happens

Duodenum—-pancreatic amylase

Brush border enzymes (maltase, sucrase & lactase) act on disaccharides
produces monosaccharides--fructose, glucose & galactose
lactose intolerance (no enzyme; bacteria ferment sugar) -- gas & diarrhea

Answer 9

digestion of carbohydrates

Question 10

Mucosal cells of small intestine fail to produce lactase
essential for digestion of lactose sugar in milk
undigested lactose retains fluid in the feces
bacterial fermentation produces gases
Symptoms
diarrhea, gas, bloating & abdominal cramps
Dietary supplements are helpful
We’re all a bit milk intolerant: infant vs. adult stomach pH

Answer 10

lactose intolerance

Question 11

HCl denatures or unfolds proteins

pepsin turns proteins into peptides

Answer 11

digestion of proteins–stomach

Question 12

digestive enzymes—split peptide bonds between different amino acids
brush border enzymes—–aminopeptidase or dipeptidase——split off amino acid at amino end of molecule or split dipeptide

Answer 12

digestion of proteins–pancreas

Question 13

Mouth----lingual lipase
Small intestine
emulsification by bile
pancreatic lipase---splits into fatty acids & monoglyceride
no enzymes in brush border

Answer 13

digestion of lipids

Question 14

Pancreatic juice contains 2 nucleases
ribonuclease which digests RNA
deoxyribonuclease which digests DNA
Nucleotides produced are further digested by brush border enzymes (nucleosidease and phosphatase)
pentose, phosphate & nitrogenous bases
Absorbed by active transport

Answer 14

digestion of nucleic acids

Question 15

Absorption into epithelial cell
glucose & galactose—-sodium symporter(active transport)
fructose—–facilitated diffusion
Movement out of epithelial cell into bloodstream
by facilitated diffusion

Answer 15

absorption of monosaccharides

Question 16

Small fatty acids enter cells & then blood by simple diffusion
Larger lipids exist only within micelles (bile salts coating)
Lipids enter cells by simple diffusion leaving bile salts behind in gut
Bile salts reabsorbed into blood & reformed into bile in the liver
Fat-soluble vitamins are enter cells since were within micelles

Answer 16

absorption of lipids

Question 17

Inside epithelial cells fats are rebuilt and coated with protein to form chylomicrons
Chylomicrons leave intestinal cells by exocytosis into a lacteal
travel in lymphatic system to reach veins near the heart
removed from the blood by the liver and fat tissue

Answer 17

absorption of lipids (2)

Question 18

Sources of electrolytes
GI secretions & ingested foods and liquids
Enter epithelial cells by diffusion & secondary active transport
sodium & potassium move = Na+/K+ pumps (active transport)
chloride, iodide and nitrate = passively follow
iron, magnesium & phosphate ions = active transport
Intestinal Ca+ absorption requires vitamin D & parathyroid hormone

Answer 18

absorption of electrolytes

Question 19

Fat-soluble vitamins
travel in micelles & are absorbed by simple diffusion

Water-soluble vitamins
absorbed by diffusion

B12 combines with intrinsic factor before it is transported into the cells
receptor mediated endocytosis

Answer 19

absorption of vitamins`

Question 20

9 liters of fluid dumped into GI tract each day
Small intestine reabsorbs 8 liters
Large intestine reabsorbs 90% of that last liter
Absorption is by osmosis through cell walls into vascular capillaries inside villi

Answer 20

absorption of water

Question 21

on test

bile salt

Answer 21

michelle

Question 22

on test

coated protein

Answer 22

chlomicron