Lecture 52: Intestinal Transport and Liver Physiology

Question 1

Why is it important to reabsorb secretions delivered to the proximal part of the small intestine?

Answer 1

reabsorption is the mechanism in which ions and fluid is recovered

Need to recover ions and fluid to maintain ECF volume and blood pressure

Question 2

Apical membranes in the intestine have ____ channels.

Answer 2

Cl- channels

Na follows Cl passively into the lumen, water follows NaCl

Question 3

The basolateral membrane in the intestine has what type of transporters?

Answer 3

Na+/K+ ATPase
Na+/K+/2Cl- co-transporter

Question 4

The permeability of tight junctions between enterocytes determines the route for fluid and electrolyte absorption. What is the route for tight vs leaky junctions?

Answer 4

If tight, then things go the transcellular route- in stomach and colon

If leaky, go the paracellular route- in duodenum and jejunum

Question 5

Is fluid absorption in the intestine hypo-osmotic, hyperosmotic, or isosmotic?

Answer 5

Isosmotic- absorb fluid and electrolytes in proportion

Question 6

The _________ is the major site for Na+ absorption.

Answer 6

Jejunum

Question 7

The ileum has an overall net absorption of ________.

Answer 7

NaCl

Question 8

In the colon, what does the synthesis of Na+ channels induced by aldosterone causes what?

Answer 8

Increased Na+ absorption AND increased K+ secretion

Question 9

What effect does a loss of large volumes of ECF-type fluid from the GIT have on the ECF volume, intravascular volume, and arterial pressure?

Answer 9

Decreased ECF volume
Decreased intravascular volume
Decreased arterial pressure

Question 10

What are issues and losses associated with severe diarrhea?

Answer 10

• Circulatory collapse
• High HCO3- losses relative to Cl losses can lead to hyperchloremic metabolic acidosis with normal anion gap
• High K+ losses

Question 11

In what area of the intestines does aldosterone increase synthesis of Na+ channels for Na+ reabsorption?
A) Duodenum
B) Jejunum
C) Ileum
D) colon

Answer 11

Colon

Question 12

The liver receives portal blood from what organs?

Answer 12

Stomach
Small intestine
Large intestine
Pancreas
Spleen

Question 13

Name the functions of the liver

Answer 13

Process absorbed substances
Synthesis and excretion of bile acids
Bilirubin production and excretion
Metabolism of nutrients
Detoxification and excretion of waste products

Question 14

The mononuclear phagocyte system removes senescent (deteriorating and old) RBC and degrades hemoglobin into what?

Answer 14

Degrades hemoglobin to biliverdin then to bilirubin

Question 15

What is jaundice?

Answer 15

Accumulation of free or conjugated bilirubin

Question 16

Urobilin and stercobilin goes where? Urobilinogen goes where?

Answer 16

Urobilin and stercobilin go out in the feces

Urobilinogen goes back to the liver

Question 17

What are the 3 mechanisms of carbohydrate metabolism in the liver? Give a brief description of each.

Answer 17

• Gluconeogenesis: Use glycerol and gluconeogenic AA to synthesize glucose after glucose stores (glycogen) are depleted
• Glycogenesis: highly branched chains of stored glucose= glycogen
• Glycogenolysis: break down glycogen to release glucose- stimulated by glucagon and epinepherine

Question 18

What roles does the liver play in protein metabolism?

Answer 18

• Synthesizes non-essential amino acids
• Modifies amino acids (so gluconeogenic AA can enter gluconeogenesis
• Synthesizes plasma proteins (albumin)
• Converts ammonia to urea

Question 19

What roles does the liver play in protein metabolism?

Answer 19

• Fatty acid oxidation
• Synthesizes lipoproteins, cholesterol, phospholipids, and bile acids