Topic 6C: Kidneys

Question 1

Function of Kidneys

Answer 1

• excretes waste products like urea

- regulates water potential of the blood(osmoregulation)

Question 2

Structure of Kidneys

Answer 2

• Cortext (outlayer)
• medulla (inner layer)
• Renal Artery
• Renal Vein
• Ureter
• Bladder
• Urethra

Question 3

What is a Nephron?

Answer 3

Long tubules along with bundle of capillaries where the blood is filtered

Question 4

How many nephrons in one kidney?

Answer 4

One million

Question 5

Stages in Ultrafiltration

Answer 5

• Blood enters the through the afferent arteriole from the renal artery
• because the diameter of the afferent a is bigger than the efferent a it causes a HIGH hydrostatic pressure at the glomerulus
• forces small molecules and liquid in the blood out of the capillaries into the bowmans capsule.
• goes through three layers
• produces the a glomerular filtrate in the bowmans capsule.
• proteins are too large to enter through

-

Question 6

What layers are involved in ultrafiltration?

Answer 6

• Capillary wall
• Basement membrane
• Epithelium of bowmans capsule

Question 7

Why cant proteins pass through to the bowmans capsule?

Answer 7

they are too large so they stay in the blood

Question 8

Structure of Nephron

Answer 8

Afferent arteriole 
Glomerulus
Efferent arteriole
Bowmans Capsule
Proximal Convoluted Tubule 
Loop of Henle 
Distal Convoluted Tubule 
Collecting Duct

Question 9

What is in the medulla?

Answer 9

Loop of Henle and Collecting Duct

Question 10

What happens in the PCT?

Answer 10

• Useful substances like glucose leave the tubules and into the capillary network by AT and FD
• Water enter the blood by osmosis because the wp of water in blood is lower than filtrate.

Question 11

Adaptations of PCT

Answer 11

• microvilli on the epithelium wall of PCT increases the SA for selective reabsorption
• lots of mitochondria provides ATP for active transport

Question 12

What is urine made up of?

Answer 12

• water
• dissolved salts
• urea
• hormones and excess vitamins

Question 13

What is osmosregulation?

Answer 13

When the kidneys regulate the water potential of blood so that the body has just the right amount of water.

Question 14

If water potential of blood is too low..

Answer 14

• more water is absorbed into the blood

- urine is more concentrated so less water is lost during excretion

Question 15

If water potential of blood is too high

Answer 15

Less water is absorbed into the blood

-urine is dilute so more water is lost during excretion.

Question 16

What does the Loop of Henle do?

Answer 16

Maintains a sodium ion gradient

- this is for the cotransport of glucose and amino acids with Na+

Question 17

How many limbs does loop of Henle have?

Answer 17

Descending and ascending limb

Question 18

Stages of Loop of Henle

Answer 18

1) Top of a limb Na+ are actively transported out into the medulla
- water stays inside because a limb is impermeable to water.
2) Creates a low water potential in the medulla because there is a high concentration of ions.
- WP gradient established
3) Water from the d limb and collecting duct diffuse out into the medulla by osmosis
- this makes the filtrate more concentrated
4) The water in the medulla is reabsorbed into the blood through the capillary network

Question 19

What causes the Na+ to be actively transported out to the medulla from the top of the ascending limb?

Answer 19

Near the bottom of the ascending limb there is an increase of Na+ions which diffuses out into the medulla.

Question 20

What happens at the distal convulted tubule?

Answer 20

Water diffuses out of the distal convoluted tubule by osmosis and is reabsorbed into the blood.

Question 21

What happens in the collecting duct?

Answer 21

• In the medulla there is a low water potential as a result of the loop of henle
• This causes water to move out of the CD by osmosis leaving the filtrate to remain in the collecting duct

Question 22

What type of cells monitors the water potential of blood?

Answer 22

osmoreceptors

Question 23

Where are osmorecptors located in the body

Answer 23

part of the brain called the hypthalamus

Question 24

What does ADH stand for?

Answer 24

Antidiuertic Hormone

Question 25

What happens to ADH when you are dehydrated?

Answer 25

• water potential of the blood drops
• detected by osmoreceptors in the hypothalmus
• sends a signal to the posterior pituitary gland (PPG)
• (PPG) is stimulated to release MORE ADH into the blood
• More ADH means that DCT and CD are more permeable to water
• so more water is reabsorbed into the blood by osmosis

Question 26

What happens to ADH when you are hydrated

Answer 26

• water potential of the blood rises
• detected by osmoreceptors in the hypothalmus
• sends a signal to the posterior pituitary gland (PPG)
• (PGG) is stimulated to release LESS ADH into the blood
• Less ADH means that DCT and CD are less permeable to water
• so LESS water is reabsorbed into the blood by osmosis

Question 27

What kind of urine do you produced if you are hydrated?

Answer 27

A large amount of dilute urine is produced and more water is lost.

Question 28

What kind of urine do you produced if you are dehydrated?

Answer 28

A small amount of highly concentrated urine is produced and less water is lost.

Question 29

Animals which live in drier climates will have

Answer 29

Animals which live in drier climates will have longer loops of Henle

Question 30

What are the effects of having a longer loops of Henle? (For animals living in drier climates)

Answer 30

• Greater amount of ions pumped out of ascending limb (filtrate) into blood.
• Creating a much lower water potential in medulla tissue
• Steeper water potential gradient created
• More water reabsorbed from collecting duct by osmosis
• Urine has a lower water potential(more concentrated)