Renal III: Tubular Reabsorption and Secretion

Question 1

What is tubular reabsorption?

Answer 1

Materials transfer from tubular fluid back into the blood

Question 2

Where does most reabsorption occur?

Answer 2

in PCT (rest of nephron does fine tuning)

Question 3

What is tubular secretion?

Answer 3

When materials are transferred from blood to tubular fluid

Question 4

How does tubular reabsorption work?

Answer 4

By active and passive processes
Water follows solutes by osmosis
Small proteins move into the blood by pinocytosis

Question 5

What is paracellular reabsorption?

Answer 5

Reabsorption between cells
50% of reabsorbed material moves between cells by diffusion

Question 6

What is transcellular reabsorption?

Answer 6

Reabsorption through cells
Material moves through both apical and basal membranes of tubule cell by active transport

Question 7

How is water reabsorbed?

Answer 7

Only by osmosis

Question 8

What is obligatory water reabsorption?

Answer 8

Water is “obliged” to follow the solutes being reabsorbed
Reabsorption always happens

Question 9

What is facultative water reabsorption?

Answer 9

Water reabsorption is under control of antidiuretic hormone (ADH)

Question 10

What do Na+ symporters do?

Answer 10

Help reabsorb materials from tubular filtrate
(Glucose, amino acids, lactic acid, water-soluble vitamins)

Question 11

What does reabsorption in the PCT rely on?

Answer 11

low intracellular Na+

Question 12

How are intracellular sodium levels kept low in the PCT?

Answer 12

by Na+/K+ pumps on basolateral side

Question 13

Is filtrate hypo, iso, or hypertonic to blood at the end of the PCT?

Answer 13

isotonic

Question 14

What do Na+ antiporters help secrete in the PCT?

Answer 14

acid, H+

Question 15

What do Na+ antiporters rely on for secretion in the PCT?

Answer 15

low intracellular Na+

Question 16

What happens when renal threshold is exceeded?

Answer 16

transport is limited

Question 17

What is a renal threshold?

Answer 17

The limits on rate of transport for renal symporters

Question 18

What reabsorption occurs in the descending limb of the loop of Henle? And is it active or passive?

Answer 18

osmosis (water reabsorption)
passive reabsorption

Question 19

What is reabsorbed in the thin ascending limb of the loop of henle? And is it passive or active?

Answer 19

NaCl
passive reabsorption

Question 20

What symporters does the thick ascending limb of the loop of henle have?

Answer 20

Na+/K+/2Cl-

Question 21

Is filtrate hypo, iso, or hypertonic at the end of the loop of henle?

Answer 21

hypotonic

Question 22

Is filtrate hypo iso, or hypertonic in the early DCT?

Answer 22

hypotonic

Question 23

The early DCT reabsorbs both ions and water, which i s it more permeable to?

Answer 23

water

Question 24

Is all water reabsorption obligatory or facultative until the late DCT?

Answer 24

obligatory reabsorption

Question 25

What two cell types are in the late DCT and collecting duct?

Answer 25

Principal cells and intercalated cells

Question 26

What is the function of principal cells in the late DCT and CD?

Answer 26

reabsorb Na+ reabsorb H2O if ADH is present secrete K+

Question 27

What is the function of intercalated cells in the late DCT and CD?

Answer 27

reabsorb K+ and HCO3- secrete H+

Question 28

How does drinking water produce dilute urine?

Answer 28

Decreases blood osmolarity Inhibits ADH release increases H2O loss in urine more water in urine = more dilute

Question 29

Does filtrate osmolarity increase or decrease as it moves down the descending limb of the loop of henle?

Answer 29

increase (more solutes than water)

Question 30

Does filtrate osmolarity increase or decrease as it moves up the ascending limb of the loop of henle?

Answer 30

decreases (solutes leave)

Question 31

Does filtrate osmolarity increase or decrease in the collecting duct?

Answer 31

decreases to produce dilute urine

Question 32

Does ADH make the late DCT and CD permeable or impermeable to water?

Answer 32

permeable, allows for maximum water reabsorption (anti-diuretic, less urine = want less water in urine)