Kidney Tubular Function

Question 1

Where does filtration take place in the kidney

Answer 1

Renal corpuscle

180 l/day

Glomerulus, bowmans capsule

Question 2

Where does reabsorption and secretion take place

Answer 2

Renal tubule

Question 3

What is included in the renal tubule

Answer 3

• proximal convoluted tubule
• loop of henle
• distal convoluted tubule
• collecting ducts

Question 4

What is the primary site of reabsorption

Answer 4

Proximal convoluted tubule

Question 5

What percentage is reabsorbed in the proximal convoluted tubule

Answer 5

65%

Question 6

How much of filtrate is reabsorbed in the the loop of Henle

Answer 6

25% is reabsorbed

Question 7

What percentage is reabsorbed in the distal conjugated tubule

Answer 7

8%

Question 8

How much sodium is reabsorbed in the kidney

Answer 8

98% Na reabsorbed - 80% energy consumption used by kidney

Question 9

What increases the surface area of the proximal convoluted tubule

Answer 9

Microvilli

Question 10

What are all portions of the nephron closely associated with

Answer 10

Closely associated with peritubular capillaries vasa recta

Question 11

What is filtered and reabsorbed in the kidney

Answer 11

• sodium
• chloride
• calcium
• phosphate
• potassium
• bicarbonate
• water
• glucose
• amino acids
• urea

Question 12

What is not reabsorbed in the kidney

Answer 12

Creatinine

Question 13

What can be measured to determine kidney health

Answer 13

Creatinine levels because it shouldn’t be reabsorbed into the kidney

Question 14

How does the filtrate move into the interstital space

Answer 14

Through passive diffusion

Question 15

What is passive diffusion

Answer 15

Movement of molecules from high to low concentration until equilibrium is reached

Question 16

What percentage of filtrate is reabsorbed into the blood

Answer 16

50% filtrate re absorbed into the blood and 50% remains in the tubule

Question 17

The proximal tube reabsorbs … of filtrate

Answer 17

The proximal tube reabsorbs 2/3 of filtrate

Question 18

What follows sodium

Answer 18

• water follows Na+ wherever it goes - osmosis
• glucose and amino acids co-transported with Na+
• chloride and negative ions follow Na+

Question 19

Where is the sodium potassium pump

Answer 19

The sodium potassium pump is on the basolateral membrane and it facilitates 65% of sodium reabsorption

Question 20

How does the sodium potassium pump facilitate nutrient reabsorption

Answer 20

By co transport

Question 21

Why does water follow sodium

Answer 21

Water follows sodium via osmosis

Question 22

Na+ active transport facilitates -

Answer 22

• 100% nutrient reabsorption - glucose and amino acids by co transport
• 65% of water reabsorption - water follows Na+
• 65% negative ions follow the electrochemical gradient
• no effect on waste removal

Question 23

How much urea is reabsorbed by passive diffusion

Answer 23

50%

Question 24

What happens to the remaining filtrate after reabsorption in the proximal convoluted tubule

Answer 24

Remaining filtrate (60l) continues through the loop of henle

Question 25

What is the function of the loop of henle

Answer 25

Counter-current multiplication for the juxtamedullary nephrons

Question 26

What are the three parts of the loop of henle

Answer 26

- thin decending limb - thin ascending limb - thick ascending limb

Question 27

What part of the loop of henle contains aquaporins

Answer 27

The thin descending limb

Question 28

Describe the thin descending limb

Answer 28

- freely permeable to water, allows movement of water into the intestinal space - does not contain active sodium pumps

Question 29

Describe the thick ascending limb

Answer 29

The site of sodium reabsorption

Question 30

What is the role of the thick ascending limb

Answer 30

Actively pumps sodium into the intestinal space and water cannot follow because there are no aquaporins

Question 31

Sodium reabsorption is via…

Answer 31

Via NKCC2 on the apical membrane

Question 32

How many molecules of chloride are co transported in the thick ascending limb

Answer 32

2 molecules of chloride

Question 33

How many molecules of potassium are co transported in the thick ascending limb

Answer 33

1 molecule of potassium

Question 34

What is the main target site for drugs in the thick ascending limb

Answer 34

The sodium potassium pump is NKCC2 is the main target site for drugs

Question 35

What conditions are created in the medullas as sodium is actively reabsorbed from the filtrate

Answer 35

The medulla becomes salty

Question 36

What happens to the water in the filtrate as it enters the loop of henle

Answer 36

The water flows out of the loop of henle by osmosis

Question 37

What happens to the concentration of the filtrate as it ascends the thick ascending limb

Answer 37

The concentration decreases The most concentrated urine will be found deep in the medulla This is called counter current multiplication

Question 38

What is the function of counter current multiplication

Answer 38

Without this process we would need to go to the toilet and drink water all of the time It’s a way to maintain a balance

Question 39

What is the vasa rectas role in counter current multiplication

Answer 39

The vasa recta maintains the concentration gradient of the medulla, this is due to the fact that the blood flow is so slow it does not wash away the gradient

Question 40

Why does the loop of henle employ counter current multiplication

Answer 40

To reabsorb water and concentrate urine

Question 41

Where is sodium actively reabsorbed in the loop of henle

Answer 41

The thick ascending limb

Question 42

The loop of henle maintains…

Answer 42

Creates and maintains high osmotic pressure within the medulla

Question 43

Function of the distal convoluted tubule

Answer 43

Fine tuning - site of fluid volume and electrolyte regulation

Question 44

Explain the role of hormones in the distal convoluted tubule

Answer 44

Sodium and water reabsorption are hormonally regulated

Question 45

What is the function of the anti-diuretic hormone (ADH)

Answer 45

Increases water reabsorption

Question 46

What is the function of aldesterone in the distal consulted tubule

Answer 46

Increases Na+ reabsorption

Question 47

What is the function of atrial natriuretic hormone (ANH) in the distal convoluted tubule

Answer 47

Promotes Na+ secretion

Question 48

What would happen if there was no hormonal regulation of the DCT

Answer 48

In the absence of external hormonal regulation a large volume of dilute (hypotonic) urine is produced

Question 49

What produces ADH

Answer 49

The pituitary gland

Question 50

How does ADH increase water reabsorption

Answer 50

Acts on distal and collecting tubules by inserting aquaporins, this allows the water to be reabsorbed from the filtrate Small amount of urine produced

Question 51

How does aldosterone act on the DCT

Answer 51

Upregulates activity and insertion of Na+K+ pumps and channels

Question 52

Describe when Atrial natriuretic hormone (ANH) would be produced and why

Answer 52

Will be released when there is an increase in blood pressure and there is too much fluid in the circulation Promotes Na+ secretion