Renal Physl 7

Question 1

What percent of filtered fluid is reabsorbed?

Answer 1

99%

Question 2

How many liters of urine is produced on average?

Answer 2

1.5L

Question 3

Why does the kidney filter so much?

Answer 3

To allow the removal of wastes and control of fluid and electrolyte balance

Question 4

What does the process of water and solute reabsorption from the filtrate to the renal interstitium heavily depend on?

Answer 4

Active transport mechanisms

Question 5

What do tubular epithelial cells do in reabsorption?

Answer 5

They actively transport solutes out of the filtrate and into the renal interstitium

Question 6

What does tubular epithelial cells actively transporting solute into the renal interstitium produce?

Answer 6

An electrochemical gradient

Question 7

How does water get reabsobed?

Answer 7

It follows the solutes through osmosis

Question 8

What creates a transepithelial electrochemical gradient?

Answer 8

The active transport of sodium ions into the renal interstitium to be reabsorbed

Question 9

After sodium ions are reabsorbed to the renal interstitium, where is more negative?

Answer 9

The lumen is more negative the the interstitium

Question 10

What happens as a result of the lumen being more negative and renal interstitium being more positive after sodium ions are actively transported out?

Answer 10

Anions follow the positively charged sodium ions into the interstitium to be reabsorbed

Question 11

After all the solutes leave the tubule lumen what is the concentration of the filtrate?

Answer 11

The filtrate becomes more dilute compared to the interstium

Question 12

What happens as a result of the filtrate being more dilute than the interstitium after the solutes enter the interstitium?

Answer 12

The water moves from the tubule lumen to the interstitium and this concentrates the remaining solutes in the tubule lumen

Question 13

What happens once the filtrate is concentrated due to water moving to the interstitium?

Answer 13

Because the solutes in the lumen are so concentrated it moves down its concentration gradient to the interstitium

Question 14

What kinds of transport does reabsorption involve?

Answer 14

Transport across tubular epithelial cells as well as paracellular transport

Question 15

What is transcellular transport?

Answer 15

When solutes pass both the apical and basal lateral membrane of the epithelia cell to get to the renal interstitium

Question 16

What occurs in the paracellular pathway?

Answer 16

Solutes pass between epithelial cells through cell junction

Question 17

What does pattern of transport (transcellular or paracellular) depend on?

Answer 17

The permeability of the epithelial cells to each solute and the electrochemical gradient

Question 18

Where does active reabsorption of sodium ions mostly take place?

Answer 18

At the proximal tubule

Question 19

What happens since sodium concentration in the lumen is higher than in the cell interior?

Answer 19

Sodium can enter the epithelial cells passively going down its electrochemical gradient at the apical membrane

Question 20

What kind of channels do sodium ions interact with when going from the lumen to the epithelial cells?

Answer 20

Symporters, antiports, and open leak channels

Question 21

What channels contribute significantly to sodium reabsorption?

Answer 21

• Sodium hydrogen exchanger or NHE channels

* ENaC (apical epithelial sodium channel)

Question 22

What transports sodium in the epithelial cell to the renal interstitium?

Answer 22

Sodium Potassium ATPase

Question 23

What happens as a result of the sodium potassium ATPase actively transporting sodium out of the epithelial cell?

Answer 23

Potassium enters the cell but it can escape back out again through the basolateral potassium leak channels

Question 24

What can the reabsorption of sodium be linked to?

Answer 24

The reabsorption of other substances through secondary active transport like amino acids, glucose, other ions and metabolites

Question 25

How is glucose reabsorption linked to sodium reabsorption?

Answer 25

The apical membrane has a sodium glucose transporter SGLT

Question 26

What keeps the intracellular levels of sodium in the epithelial cells low?

Answer 26

The basolateral membrane active transport of sodium out of epithelial cells

Question 27

What happens as a result of the active transport of sodium out of epithelial cells?

Answer 27

Sodium can continue to move into the cells down its electrochemical gradient

Question 28

What happens to glucose as a result of sodium being able to move down its electrical chemical gradient?

Answer 28

The energy can be used to power the apical sodium glucose transporter and facilitate the movement of glucose into the cell against its own concentration gradient

Question 29

What happens as intracellular glucose concentration rises?

Answer 29

Its facilitated diffusion into the interstitium occurs via basal lateral glucose transporters

Question 30

How can Urea be reabsorbed?

Answer 30

It can diffuse through epithelial cell junctions if there is a sufficient concentration gradient

Question 31

What drives water reabsorption from the lumen?

Answer 31

Reabsorption of sodium and other solutes

Question 32

Can proteins cross the glomerular capillaries?

Answer 32

Very small proteins and peptides can cross the filtration barrier

Question 33

Where in the tubule are can reabsorption of proteins occur?

Answer 33

In the proximal tubule

Question 34

How are proteins reabsorbed in the proximal tubule?

Answer 34

Receptor mediated endocytosis at the apical membrane brings them into the epithelial cell. The proteins are broken down by lysosomes into amino acids which are transported to the interstitium

Question 35

What happens if all reabsorption transporters are occupied?

Answer 35

The transport maximum for a substance will be reached and the excess solute will be excreted in the final urine

Question 36

What is a situation where reabsorption transporters will be satuarated?

Answer 36

In diabetic patients, circulating glucose maximizes occupation of apical sodium glucose transporters and glucose can’t be reabsorbed and is detected in the urine

Question 37

What allows solutes and water to enter the peritubular capillaries after being in the interstitium?

Answer 37

The low hydrostatic pressure within the peritubular capillaries and higher colloid osmotic pressure due to a concentration of plasma proteins favors the movement of water and solutes from the interstitium into the capillaries by bulk flow