Kidneys

Question 1

What may cause a hypertonic blood

Answer 1

Too much sweating
Not drinking enough water
Lots of ions in diet

Question 2

What may cause hypotonic blood

Answer 2

Drinking too much water

Not enough salt in diet

Question 3

Structure of nephron

Answer 3

Afferent arteriole leading into nephron
Branches into smaller capillaries called the glomerulus inside the renal capsule
Leading into proximal convoluted tubule
Loop of henle
Distal convoluted tubule
Collecting duct

Question 4

What’s in urine

Answer 4

Water
Dissolved salts
Urea
Small substances like hormones

NO PROTEIN OR BLOOD

Question 5

Kidney function

Answer 5

Filter blood to remove waste and selectively reabsorbed useful substances into blood

Question 6

Why no proteins in wee

Answer 6

Too large to be filtered out

Question 7

Why no glucose in wee

Answer 7

All absorbed in selective reabsorption by active transport in PCT

Question 8

4 steps for filtering and reabsorption

Answer 8

Ultrafiltration
Selective reabsorption
Loop of henle
DCT and collecting duct

Question 9

What causes the high hydrostatic pressure in ultrafiltration

Answer 9

Blood enters through afferent arteriole and spots into lots of smaller capillaries which make up the glomerulus

Question 10

Adaptation of cells lining PCT

Answer 10

Microvilli provide a large surface area for reabsorption

Lots of mitochondria since need energy for active transport of glucose

Question 11

Function of loop of henle

Answer 11

Maintains a sodium ion gradient to enable reabsorption of water

Question 12

Ascending vs descending limb

Answer 12

Ascending is permeable to water, descending impermeable

Question 13

Hypotonic blood, osmoregulation

Answer 13

Osmoreceptors in hypothalamus detect rise in water potential
Water enters osmoreceptors via osmosis
Triggers posterior pituitary gland to secrete less ADH
Less travels in blood to kidneys
Decreases permeability of distal convoluted tubule and collecting duct to water
By causing less vesicles to fuse with the cell membrane of these cells

Large volume of urine produced
Dilute
Less water reabsorbed at DCT and collecting duct

Question 14

Hypertonic blood, osmoregulation

Answer 14

Osmoreceptors in hypothalamus detect fall in water potential
Water leaves osmoreceptors via osmosis
Triggers posterior pituitary gland to secrete more ADH
More travels in blood to kidneys
Increases permeability of distal convoluted tubule and collecting duct to water
By causing more vesicles to fuse with the cell membrane of these cells

Small volume of urine produced
Concentrated
More water reabsorbed at DCT and collecting duct

Question 15

How is urea removed from the blood

Answer 15

Hydrostatic pressure caused by fenestrations of capillary wall
Causes ultrafiltration at renal capsule/glomerulus
Through basement membrane which acts as a filter
Enabled by small size of urea molecules

Question 16

How is a glomerular filtrate produced

How does ultrafiltration work

Answer 16

Higher than normal hydrostatic pressure caused by fenestrations in capillary endothelium
Water, glucose, urea pass through basement membrane which acts as a filter
Pass through spaces between branches of podocytes
Protein and blood molecules too large to stay behind

Question 17

Explain the reabsorption of water and glucose

Answer 17

Sodium ions actively transported out of the cells lining the proximal convoluted tubule
Into blood capillaries to reduce sodium concentration in cells
Via sodium potassium pump which required ATP from many mitochondria
Allowing sodium ions from filtrate to move into surrounding cells via facilitated diffusion via co-transport with glucose
Allowing glucose to be reabsorbed

Question 18

Thicker medulla

Answer 18

Longer loop of Henle
Sodium ion concentration gradient can be maintained over a longer length
More sodium ions actively transported out of ascending loop of henle
More water reabsorbed

Question 19

How is urea concentrated in the filtrate

Answer 19

Reabsorption of water by osmosis
At the PCT/Descending loop of henle
At the DCT/CD active transport of ions/glucose

Question 20

How does ADH cause movement of water from lumen to collecting duct

Answer 20

Vesicles containing aquaporins inserted into cell membranes of CD
Water enters via osmosis through aquaporins
Down a water potential gradient
From cell to capillary
Via interstitial fluid

Question 21

How do the descending and ascending loops work

Answer 21

Filtrate enters descending limb and exits ascending limb
Sodium ions actively transported out of the Ascending limb using ATP
Sodium ions enter Descending limb
Lowering water potential between the two limbs
Water drawn out of permeable descending limb by osmosis into medulla
As the ascending limb is impermeable to water little/no water leaves that part of the loop
Water from the descending limb then enters capillaries returning to the blood

Question 22

DCT

Answer 22

Makes final adjustment to the water and salts that are reabsorbed
Permeability of its walls alters under influence of certain hormones
Water continues to move out by osmosis the counter current multiplier ensures there is always a water potential gradient
Water out of CD into tissue fluid then surrounding capillaries