Absorption

Question 1

Water balance

Answer 1

there is lots of secreted, ingested fluid so the small intestine absorbs (7000 ml 78%), the colonic absorption (1900 mL -21%) and stool 100 mL (1%)

Water absorption:
Hypoosmotic chyme- water diffuses into cells by osmosis
Hyperosmotic chyme- water moves from plasma into chyme

Question 2

small intestine structure

Answer 2

Valvulae conniventes covered by villi. brush border pino cytotic vesicles

Question 3

sodium absorption

Answer 3

in the intestine 140 in the cells only 50 (gradient mainted by the Na/k transporter. Na absorbtion co transports glucose and AAs into the cells. It counter transports H. The H in the intestines are buffered by the Hco3 given by the HcO3/CL counter transport. The high cl in the cell is spit out of the cells in the interstitium via facilitated diffusion

Question 4

Chloride and bicarb absorption

Answer 4

Chloride absorption- follows movement of sodium in duodenum and jejunum

Bicarb absorption- large amounts of bicarb from pancreatic and hepatic secretion comines with hydrogen to form carbonic acid that dissociates into water and co2. the co2 is respired out and the water is absorbed

occurs in duodenum and jejunum

Question 5

Calcium, iron, potassium, magnesium, phosphate, bile salts, and B12 absorption

Answer 5

calcium and iron absorption- in duodenum

potassium, magnesium, phosphate- throughout

bile salts, Vit B12- ileum

Question 6

CArb absorption

Answer 6

80 % absorbed as glucose
20% absorbed as galactose and fructose

glucose and galactose absorbed with sodium via active transport

fructose does not utilize sodium transport

Question 7

Protein absorption

Answer 7

majority are absorbed by co transport with sodium

several AAs have theyre own transpoters

Question 8

Fat absorption

Answer 8

micelles move to cell surface and the monoglycerides and fatty acids difuse out of the micelle into the interior of the cell

upon absorption into the cell, they are reconverted into triglycerides and absorbed into lyphatics and go to blood as chylomicrons

small amounts of short and medium chain FAs are directly absorbed without converstion

Question 9

Celiac sprute

Answer 9

diarrhea from malabsorption, weight loss, gluted

Question 10

large intestine

Answer 10

1500 mls enters colon but normally 100-200 mls are excreted in stool
proximal colon absorption, distal colon- storage

sodium and chloride are actively absorbed via Aldosterone

Bicarb is secreted (like ileum) and echanged for chloride. the bicarb neutralizes bacterial waste

Sodium and chloride absorption causes gradient that results in absorption of water