pk

Question 1

What is the primary function of the jejunum?

Answer 1

The jejunum is primarily involved in the absorption of nutrients and electrolytes.

Question 2

What are the key mechanisms of Na⁺ absorption in the jejunum?

Answer 2

1. Na⁺/Glucose Co-transport (SGLT1): Na⁺ is absorbed with glucose or galactose.
2. Na⁺/Amino Acid Co-transport: Na⁺ is absorbed with amino acids.
3. Na⁺/H⁺ Exchange (NHE3): Na⁺ is absorbed in exchange for H⁺, maintaining pH balance.

Question 3

How is Cl⁻ absorbed in the jejunum?

Answer 3

1. Passively through paracellular pathways due to the electrochemical gradient created by Na⁺ absorption.
2. Via Cl⁻/HCO₃⁻ exchange, where Cl⁻ is absorbed in exchange for HCO₃⁻ secretion.

Question 4

How is water absorbed in the jejunum?

Answer 4

Water follows the osmotic gradient created by Na⁺ and nutrient absorption.

Question 5

What is the primary function of the ileum?

Answer 5

The ileum absorbs electrolytes, water, bile salts, and vitamin B₁₂, and can secrete Cl⁻.

Question 6

How is Na⁺ absorbed in the ileum?

Answer 6

1. Via Na⁺/glucose co-transport and Na⁺/H⁺ exchange (similar to the jejunum).
2. Na⁺/Bile Salt Co-transport: Na⁺ is absorbed with bile salts via the ASBT transporter.

Question 7

How is Cl⁻ secreted in the ileum?

Answer 7

1. Via the CFTR channel, regulated by cAMP.
2. Cl⁻ secretion is coupled with HCO₃⁻ secretion to neutralize acidic chyme.

Question 8

How is K⁺ absorbed in the ileum?

Answer 8

K⁺ is absorbed passively through paracellular pathways due to the electrochemical gradient.

Question 9

What is the primary function of the colon?

Answer 9

The colon absorbs water and electrolytes, concentrating fecal material.

Question 10

How is Na⁺ absorbed in the colon?

Answer 10

1. Via Epithelial Sodium Channels (ENaC), driven by the Na⁺/K⁺-ATPase pump.
2. Via Na⁺/H⁺ Exchange (NHE3).

Question 11

How is Cl⁻ absorbed in the colon?

Answer 11

1. Via Cl⁻/HCO₃⁻ exchange, where Cl⁻ is absorbed in exchange for HCO₃⁻ secretion.
2. Passively through paracellular pathways.

Question 12

How is K⁺ transported in the colon?

Answer 12

1. Absorption: Passively through paracellular pathways.
2. Secretion: Via apical K⁺ channels, driven by the electrochemical gradient created by Na⁺/K⁺-ATPase.

Question 13

How is HCO₃⁻ transported in the colon?

Answer 13

HCO₃⁻ is secreted in exchange for Cl⁻ absorption, neutralizing acidic byproducts of bacterial fermentation.

Question 14

How is water absorbed in the colon?

Answer 14

Water absorption is driven by the osmotic gradient created by Na⁺ and Cl⁻ absorption.