Exam 4 - Digestive System 4

Question 1

Where does nearly all chemical digestion and nutrient absorption occur?

Answer 1

in small intestine

Question 2

Small intestine must have…

Answer 2

• large surface area exposed to chyme
  It is the longest part of digestive tract

“small” refers to diameter not length

Question 3

Location of small intestine

Answer 3

retroperitoneal along w/ pancreas (posterior to stomach)

Question 4

Jejunum

Answer 4

• found primarily in “umbilical region”

- MOST DIGESTION AND NUTRIENT ABSORPTION OCCURS HERE

Question 5

Ileum

Answer 5

Has PEYER’S PATCHES - clusters of lymphatic nodules

• ends at ileocecal junction w/ large intestine
• HAS SPHINCTER KNOWN AS THE ILEOCECAL VALVE THAT REGULATES THE PASSAGE OF FOOD RESIDUE INTO THE LARGE INTESTINE (division from small intestine and large intestine)

Question 6

What doe the jejunum and ileum have in common?

Answer 6

they are both intraperitoneal - are covered w/ serosa

Question 7

Circular folds

Answer 7

involve only mucosa and submucosa (SLOWS CHYME AND PROMOTES MIXING AND ABSORPTION)

Question 8

Villi

Answer 8

• most nutrients absorbed by blood CAPILLARY

- most fat absorbed by LACTEAL

Question 9

Microvilli

Answer 9

• is the “brush border” on cells

- BRUSH BORDER ENZYMES USED FOR FINAL STAGES OF DIGESTION

Question 10

Crypts

Answer 10

pores opening between villi (inverse villi that go into the mucosa)

Question 11

What are crypts comprised of?

Answer 11

Goblet cells (secrete mucus)
Paneth cells (provide antibacterial secretions such as lysozyme, phospholipase, and defensins)
Absorptive cells

cover it
destroy the bad stuff
absorb what’s left

Question 12

Submucosa

Answer 12

(underneath the muscularis layer)

BRUNNER’S (duodenal) GLANDS in submucosa SECRETE BICARBONATE MUCUS

Question 13

Peyer Patches

Answer 13

populations of lymphocytes to fight pathogens (not absorptive since it’s in the submucosa)

Question 14

Segmentation

Answer 14

purpose is to MIX AND CHURN, not to move material along

Question 15

Peristalsis

Answer 15

gradual MOVEMENT of contents towards colon

Question 16

Chemical digestion of carbohydrates summary (what we’ve done so far)

Answer 16

mouth - salivary amylase
esophagus and stomach - N/A (pH is too low_
duodenum - pancreatic amylase

Question 17

What acts on DISACCHARIDES to make them monosaccharides?

Answer 17

brush border enzymes:
Maltase
Lactase
Sucrase

Question 18

Lactose intolerance

Answer 18

exists when lactase is ABSENT and bacteria ferment undigested sugar; leads to excessive intestinal gas and diarrhea

Question 19

What should you tell someone who has had a diarrhea episode?

Answer 19

Tell them to avoid dairy until the gut has healed itself; BRAT diet, bananas, rice, apple sauce, toast

Question 20

What is in cotransport w/ Na?

Answer 20

SODIUM-GLUCOSE TRANSPORT PROTEINS (SGLT) in membrane help absorb GLUCOSE and GALACTOSE

Question 21

How is FRUCTOSE absorbed?

Answer 21

by FACILITATED DIFFUSION then converted to glucose inside the cell

Question 22

Digestion of proteins in the stomach

Answer 22

• HCl denatures or unfolds proteins

- pepsin turns proteins into peptides

Question 23

Digestion of proteins in the small intestine

Answer 23

Trypsin and Chymotrypsin “take over” protein digestion by breaking polypeptides into OLIGOPEPTIDES (small chunks)

Question 24

What breaks down oligopeptides one amino acid at a time?

Answer 24

Carboxypeptidase
Aminopeptidase
Dipeptidase

Question 25

from pancreas; removes amino acids from -COOH end

Answer 25

Carboxypeptidase

Question 26

from brush border; removes amino acids from -NH2 end

Answer 26

Aminopeptidase

Question 27

from brush border; splits dipeptides in middle

Answer 27

Dipeptidase

Question 28

Absorption of proteins

Answer 28

amino acid cotransporters (active transport w/ Na or H ions / symporters) move into epithelial cells and facilitated diffusion moves amino acids out into blood stream

Question 29

How do infants absorb proteins?

Answer 29

by pinocytosis; which allows for absorption of protective maternal IgA (allows for passive immunity)

Question 30

Why do lipids have more complex digestion and absorption?

Answer 30

because they're hydrophobic

Question 31

What increase surface area of exposure for lipases?

Answer 31

Lecithin and bile salts (emulsification droplets)

Question 32

Types of lipases

Answer 32

- lingual lipase activated by stomach acid | - pancreatic lipase

Question 33

Fat hydrolysis

Answer 33

emulsification droplets acted upon by pancreatic lipase, which hydrolyzes the 1st and 3rd fatty acids from triglycerides, usually leaving the middle fatty acid

Question 34

role of Micelles

Answer 34

micelles in the bile pass to the small intestine and pick up several types of dietary and semidigested lipids

Question 35

Important note about micelles

Answer 35

micelles start in the bile as ONLY collection of bile acids; they ACQUIRE the lipid core later as they travel down the intestine

Question 36

What are micelles?

Answer 36

minute droplets of bile that wrap above products

Question 37

first step of lipid absorption

Answer 37

lipids move to surface of intestinal absorptive cells where they leave the micelles and diffuse into cells

Question 38

Chylomicron

Answer 38

within the intestinal cells triglycerides are reformed and covered w/ cholesterol "coat" and protein; chylomicron is moved into secretory vesicles and released into core of villus

Question 39

What takes up chylomicrons?

Answer 39

chylomicrons are generally too big to enter capillaries so they are taken up by LYMPHATIC LACTEAL

Question 40

Where do chylomicrons travel from lacteal?

Answer 40

they travel in lymph system through CISTERNA CHYLI and THORACIC DUCT into LEFT SUBCLAVIAN VEIN

Question 41

Percentage of cholesterol in our bodies

Answer 41

15% - ingested | 85% - manufactured in LIVER and INTESTINAL MUCOSA

Question 42

Extremely low density; enter lymph

Answer 42

Chylomicrons

Question 43

FORM IN WHICH LIPIDS LEAVE THE LIVER; converted to LDL

Answer 43

VLDL

Question 44

Where do triglycerides removed from VLDL go to?

Answer 44

stored in adipose cells

Question 45

TRANPORTS CHOLESTEROL TO CELLS

Answer 45

LDL; cells have LDL receptors; # of LDL receptors become less once cell's lipid/cholesterol needs are met (if you have excess it will deposit in other areas of the body)

Question 46

TRANSPORTS EXCESS CHOLESTEROL FROM CELLS TO LIVER

Answer 46

HDL; gets ride of cholesterol in the body, allows for excretion