the kidney

Question 1

name the 8 parts of the nephron

Answer 1

• bowmans capsule
• glomerulus
• proximal convoluted tubule (PCT)
• LOOP OF HENLE:
- ascending limb
- descending limb
• distal convoluted tubule (DCT) 
•collecting duct

Question 2

what’s the process that happens in the bowmans capsule & glomerulus?

Answer 2

ultrafiltration

Question 3

explain the process of ultrafiltration

Answer 3

• afferent has wider lumen than efferent arteriole
• blood under high hydrostatic pressure
• large proteins, RBC, WBC too big to pass through so remain in capillary as blood plasma
• small proteins, glucose, amino acids, ions, urea + water filters through to form glomerulus filtrate
• endothelium of capillary has pores
• bowmans capsule has podocytes (slits)

Question 4

what is the process that happens in the PCT?

Answer 4

selective reabsorption

Question 5

explain selective reabsorption in terms of the structure of the PCT

Answer 5

• 85% of filtrate reabsorbed back into the capillaries
• microvilli increase SA
• infolding at the base (near lumen of capillary = large SA to transfer reabsorbed substances)
• high density of mitochondria provides ATP for active transport

Question 6

explain selective reabsorption in terms of the movement in the PCT

Answer 6

• sodium ions actively transported out of the PCT into the capillary
• blood takes sodium away so lowers sodium concentration in capillary
• sodium can move down concentration gradient via facilitated diffusion through carrier proteins
• co transport of glucose, amino acids etc
• water reabsorbed

Question 7

what is the process that happens in the loop of henle?

Answer 7

reabsorption of water

Question 8

what makes up the loop of henle

Answer 8

ascending limb and descending limb

Question 9

what happens in the ascending limb

Answer 9

• has wider, thicker walls impermeable to water
• sodium is actively transported out using ATP
• now a low WP in medulla
• as filtrate moves up the ascending limb, more ions are actively transported out which increases the WP

Question 10

what happens in the descending limb

Answer 10

• permeable to water

* water moves via osmosis out into the medulla and eventually enters the blood capillaries (and is carried away)

Question 11

what is the process that happens in the DCT?

Answer 11

reabsorption of inorganic mineral ions & regulation of pH

Question 12

explain what happens in the DCT

Answer 12

• lots of microvilli to increase SA
• make final adjustments to the water and salts that are absorbed
• control pH

Question 13

what is the process that happens in the collecting duct

Answer 13

osmoregulation

Question 14

explain what happens in the collecting duct

Answer 14

• permeable to water
• space between collecting duct and ascending limb differs in WP
• cortex has a high WP, low ion conc
• medulla has a low WP, high ion conc
• water moves out via osmosis, travelling through aqua porins
• hormone ADH can alter the number of aqua porins and therefore control water loss

Question 15

what is the counter current multiplier

Answer 15

• filtrate in collecting duct with a lower WP meets interstitial fluid that has an even lower WP
• this is because there’s a counter current flow between the 2 fluids
• means that the WP gradient between the 2 exists for the whole length of the collecting duct
• therefore a steady flow of water into the interstitial fluid so around 80% of the water enters the fluid and hence the blood

Question 16

name all the parts of the kidney

Answer 16

• renal cortex
• nephron
• renal medulla
• renal pelvis
• renal artery
• renal vein
• ureter