Lecture 3- Tubular Processes

Question 1

Filtration

Answer 1

Occurs at glomerular capillary to form protein-free filtrate in bowman’s capsule

Question 2

Reabsorption

Answer 2

Process by which substances move from renal tubular lumen into the interstitium and peritubular capillary

Question 3

Secretion

Answer 3

Process by which substances move from peritubular capillaries and interstitium into tubular lumen EXCLUDING filtration

Question 4

Amount excreted

Answer 4

Ux * V

Question 5

Amount filtered

Answer 5

Px * GFR or Px * Cin

*excretion and filtration is equal for a substance that is neither reabsorbed or secreted

Question 6

Reabsorption caculations

Answer 6

A substance is reabsorbed when the amount filtered is greater than the amount excreted

Tx (amount reabsorbed) = amount filtered minus amount excreted = Cin * Px - Ux *V

Reabsorbed substances= H2O, Na+, Cl-, HCO3, K+

Question 7

Secretion calculations

Answer 7

A substance is secreted when the amount excreted is greater than the amount filtered

Amount secreted= amount excreted minus amount filtered= Uxx * V - Cin * Px

Secreted substances= K+, H+, NH3

Question 8

Tubular transport maximum (Tm)

Answer 8

For reabsorption and secretion

Maximum amount of a substance that can be secreted or reabsorbed by the tubules

Question 9

Splay

Answer 9

Represents the difference between calculate tubular maximum and actual tubular maximum

Difference between the two is due to the fact that some nephrons have lower Tm values than others