Fluid, Electrolytes and digestion

Question 1

GI function

Answer 1

Take relatively large solids, digest them into smaller molecules that can be absorbed as nutrients, while still serving as a barrier to toxins, bacteria, parasites

Question 2

Roughly how long is the small intestine

Answer 2

6m

Question 3

How is water absorbed?

Answer 3

Glucose and 2Na+ transported from intestinal lumen to epithelial cells.

Na+/K+ ATPase moves Na+ from epithelial cells to blood and K+ from blood to epithelial cells.

Water follows Na+ into blood.

Question 4

Intestinal Secretion

Answer 4

Cl- enter crypt epithelial cell by cotransport with Na+ and K+.

Na+ pumped back out via Na+ pumps and K+ is exported via channels.

Activation of adenylyl cyclase by secretagogues leads to cAMP generation.

Activates the CFTR , secretes Cl- into lumen.

Electric potential that attracts sodium pulling into lumen across tight junctions.

Net result is secretion of NaCl.

Creates osmotic gradient across tight junction and water drawn into lumen.

Question 5

Factors influencing absorption

Answer 5

Number and structure of enterocytes, blood and lymph flow, nutrient intake, GI motility

Question 6

How does cholera induce diarrhoea?

Answer 6

Cholera toxin released from bacteria and binds to intestinal cells.
Stimulates adenylate cyclase to produce cAMP
Dramatic efflux of ions and water.
Water diarrhoea

Question 7

How to medicines to treat diarrhoea work?

Answer 7

Contains glucose and sodium.
SGLT1-sodium glucose co-transporter which moves Na and glucose from the luminal membrane into the enterocyte.

Water follows sodium due to osmotic gradient.

Question 8

Digestion

Answer 8

Breakdown of large, complex organic molecules that can be used by the body

Mechanical (chewing, churning) and chemical (enzymes)

Question 9

How is glucose and galactose absorbed?

Answer 9

Through Na-dependent secondary active transport process

Question 10

How is fructose absorbed?

Answer 10

Facilitated transport