Stucture and function of the nephron

Question 1

What is the function of the nephron?

Answer 1

= create urine, filtering blood to remove waste

Question 2

What does urine contain?

Answer 2

= water
= dissolved salts
= urea
= other small substances

Question 3

What does urine not contain?

Answer 3

= proteins- to alrge to be filtered by blood
= blood cells
= glucose- reabsorbed at selective reabsorption stage

Question 4

What is stage 1:

Answer 4

= ultrafiltration- high hyfrostayic pressure
= water and small molecules are forced out of the glomerus capillaries, through the basement membrane into the renal capsule

Question 5

What is stage 2:

Answer 5

= selective reabsorption
= occurs in proximal convuluted tube

Question 6

What is stage 3 + 4?

Answer 6

= loop of henle, maintains a sodium ion gradient, so water can be reabsorbed into the blood

Question 7

What is stage 5 and 6?

Answer 7

= water moves out of the distal convulted tube, and collecting duct, tp return back to blood,
= collectinf duct, carries remaining liquid, urine to the ureter

Question 8

What is ultrafilration?

Answer 8

= blood enters through the afferent arteriole, splits into smaller cappilaries, glomerulus, causes a high hydrostatic pressure of blood
= water and small molecules sych as glucose and mineral ions, arenforced out the cappilaries through the basement membrane , and for the glomuerus filtrate
= large proteins and blood cells are too big to fit through the gaps, into the cappilairy endothelium, so remain in the blood this blood leaves by the efferent arteriole

Question 9

What is selective reabsorption?

Answer 9

= proximinal convulted tubule
= gloumerus filtrate is reabsorbed back into the blood leaving the urea, amd excess urea and mineral ions behind
= microvilli provides a large surfa e area for reabsoroptuion
= lots of mitochondria to procice energy for actiev transport

Question 10

How does selective reabsorption happen?

Answer 10

= concentration of sodium ions in the PCT, is low, as sodium ions are acticley treanspored, out of the PCT cells, into the blood of the cappilaries
= due to the concentration gradient, sodium ions diffuse down the gradient, from the lumen of the PCT into the cell linging of the {CT, this is co transport as it brings glucose with it
= this is how glucose is reabsorbed, glucose diffuse from PCT into epithelial cells into blood sram

Question 11

How is a sodium ion gradient maintained in the loop of henle?

Answer 11

= allows reabsoroptuion of water
= has an acscending- impermeable to water and thicker wall, sodium ions are activley transpored out
descending limb,

descending kimb:
= thinner [permeable to water ater moves out by osmosus to be reabsorbed into blood

Question 12

How is this maintained?

Answer 12

= mitochondria in the walls of the loop of henle, provides energy to activley transport sodium ions, out of the ascending limb of the loop of henle- accumulation of the sodium ions outside of the nephron in the medulla, lowers water potential
= water diffuses out by osmosis, into the intersterial space, and then the blood cappilaries, water is reabsorbed back into blood

Question 13

What happens at the base of the ascending limb?

Answer 13

= some sodium ions are transported, about by diffusion, as there is now a very dilute solution, due to all the water that has moved out

Question 14

what do podocytes do?

Answer 14

add another filitration layer wraps around the cappilaries
=3 filtrations, gaps between endpthelium nasmenet membrane and podyctes

Question 15

what happens when the filtrate reaches the dct?

Answer 15

= dilute- due to sodium ions being transported
= flyrate moves out of te dct, and into collecting duct, this section of medulla is concentrated,
= more water moves out the dctm and collecting duct,
= what remains forms the urine