Proximal Tubule

Question 1

What is the convoluted part of the proximal tubule also called?

Answer 1

Pars convoluta

Question 2

What is the straight portion of the proximal tubule called?

Answer 2

Pars recta

Question 3

What structure increases the surface area available for absorption on the luminal surface?

Answer 3

Brush border of microvilli

Question 4

Does sodium entry into the cell occur actively or passively?

Answer 4

Passively down a large electrical gradient and a chemical concentration gradient

Question 5

What is the function of Na-H-exchanger 3 (NHE3)?

Answer 5

Na+ entry into cell in exchange for H+ secretion

Question 6

What transporter extrudes sodium from the cells?

Answer 6

Na+/K+ ATPase

Question 7

What is the ratio of transport by the Na+/K+ ATPase?

Answer 7

3Na+ leave for 2K+ entering

Question 8

What are the 2 main mechanisms whereby Cl- is absorbed from the tubular lumen into the cells?

Answer 8

1. By antiport in exchange for the secretion of other anions (mainly HCO3- secretion, and formate HCOO-)
2. Passively

Question 9

What does HCOO- combine with in the tubular lumen?

Answer 9

Secreted H+

Question 10

Where does HCOOH go?

Answer 10

Diffuses back into the cells, where it can dissociated into H+ (for re-secretion in exchange for Na+) and HCOO- (for re-secretion in exchange for Cl-)

Question 11

Is Cl- movement active or passive?

Answer 11

Both!