Renal structure and function

Question 1

How many nephrons are in the human kidney?

Answer 1

1.5 million

Question 2

What does the nephron control? (3)

Answer 2

Glomerular filtration
Tubular reabsorption and secretion
Urine formation

Question 3

What are the 2 components in the kidney?

Answer 3

Vascular and tubular

Question 4

What are the 3 levels of the kidney?

Answer 4

Cortex
Outer medulla
Inner medulla

Question 5

What are 3 vital parts of the nephron pathway?

Answer 5

Glomerulus
Macula densa
Collecting duct

Question 6

What is the order of structures in a nephron as the blood flows? (7)

Answer 6

1. Ultrafiltration in the Bowman’s capsule
2. Proximal convoluted tubule
3. Thin descending limb (Loop of Henle)
4. Thin ascending limb (Loop of Henle)
5. Thick ascending limb
6. Distal convoluted tubule
7. Collecting duct (descending)

Question 7

What are the names of the 2 arteries that enter the kidney and what lies between them?

Answer 7

Efferent (takes away)
Granular cells, macula densa cells (ascending loop of Henle limb)
Afferent

Question 8

What do the 2 arteries feed into?

Answer 8

Glomerulus within the Bowman’s capsule

Question 9

What tube leads out of the Bowman’s capsule?

Answer 9

Proximal tubule

Question 10

What blood does the afferent arteriole deliver?

Answer 10

O2 rich blood to be filtered

Question 11

What is glomerular filtration rate dependent upon? (5)

Answer 11

Capillary permeability
Hydrostatic pressure in capillaries
Hydrostatic pressure in tubules
Osmotic pressure of plasma in glomerular capillaries
Osmotic pressure of tubular filtrate

Question 12

What is the order, hydrostatic movement and osmotic movement during glomerular filtration? (4)

Answer 12

1. Hydrostatic pressure: Bowman’s capsule, movement IN
2. Hydrostatic pressure: capillary, movement OUT
3. Colloid osmotic pressure: Bowman’s capsule, movement OUT
4. Colloid osmotic pressure: capillary, movement IN

Question 13

What are the effects of afferent constriction? (4)

Answer 13

Increased resistance
Reduced capillary pressure
GFR decreases
Bottleneck effect

Question 14

What are the effects off efferent constriction? (3)

Answer 14

Increased pressure in capillary
Pressure rises
GFR increases

Question 15

What are the key factors of the proximal convoluted tubule? (2)

Answer 15

• Filtrate (isosmotic - same no. of solutes as capillary side)
• 70% of filtrate is reabsorbed back into the body

Question 16

What is the rate of GFR per day? (2)

Answer 16

180L per day

3L plasma in the body - very efficient

Question 17

What are the key functions of the PCT? (4)

Answer 17

• Fluid entering the PCT has similar composition to plasma
• Active reabsorption of Na+ (water follows sodium)
• Reabsorption of glucose and bicarbonate
• Some ions and molecules are secreted into the tubular filtrate

Question 18

What happens in the loop of Henle? (8)

Answer 18

1. Filtrate is isosmotic from PCT
2. Water moves out as you go down
3. NO active ion transport
4. Filtrate becomes hyper-osmotic
5. Filtrate rises up the ascending limb
6. Active reabsorption of Na+
7. Impermeable to water
8. filtrate becomes hypo-osmotic

Question 19

When does the loop of Henle move from the cortex into the medulla?

Answer 19

Cortex - 300mosm/kg

Medulla - 600-1200mmosm/kg

Question 20

What is the countercurrent multiplier?

Answer 20

Facilitates the reabsorption of water from the collecting ducts toward the hyper-osmotic interstitium

Question 21

What is the role of the distal convoluted tubule? (3)

Answer 21

• Active reabsorption of Na+
• Secretion of K+ and H+ ions
• Stimulated by the actions of aldosterone

Question 22

What is the role of the collecting duct?

Answer 22

> Urea is free to move out of collecting duct in the presence of ADH
ADH opens aquaporins, thereby increasing reabsorption of water and concentrating urine

Question 23

What specific ion do we need from our diet as we struggle to reabsorb it?

Answer 23

Potassium