16. The urinary system (Greg Michael)

Question 1

What is the overall function of the kidneys?

Answer 1

Regulation of the blood composition

Control of the blood pressure and volume

Question 2

Describe the general structure of the kidney

Answer 2

Concave medially - this is the hilum where there is the renal pelvis and the major vessels
There are set lobes of the kidney and these are composed of lobules
The outer region of the kidney is the cortex and the inner region is the medulla
The medulla consists of medullary pyramids which are cone shaped tissues, ending in papillae (points)

Question 3

What is the renal pelvis?

Answer 3

The broadened top part of the ureter into which the kidney tubules drain - first part of the kidney after the hilum

The calyces all come together to form the renal pelvis

Question 4

What is a renal calyx?

Answer 4

This is a chamber of the kidney through which urine passes before going to the renal pelvis and the ureter

Question 5

Give the intricate vasculature of the kidney

Answer 5

Renal artery - main branch of the renal artery - interlobar artery - arcuate artery - interlobular artery
(LOOK AT IMAGE)

Question 6

What is the nephron of the kidney?

Answer 6

Basic structural and functional unit of the kidney

Funnel shaped epithelial structure - where a blood filtrate is processed to ultimately leave urine

Composed of Bowman’s capsule and the renal tubule

Question 7

What is the renal corpuscle?

Answer 7

Renal corpuscle being the renal body

This is Bowman’s capsule with the glomerulus supported by cells and the ECM

Question 8

What is the purpose of the ‘vascular pole’ of the renal corpuscle?

Answer 8

There is a vascular pole causing the glomerulus to have a negative charge
This means that the albumin remains in the blood rather than being filtered out into the urine

Question 9

What is the function of the renal corpuscle?

Answer 9

Ultrafiltration of the blood

Question 10

What is the ultrafiltration of the blood at the glomerulus dependant on and why?

Answer 10

Dependant on the size and charge of the components of the blood
Size: anything below molecular weight of 55,000 will automatically be filtered out
Charge: due to the vascular pole which carries a negative charge

Question 11

What are the components of the glomerular filtration barrier?

Answer 11

Fenestrated capillary
Specialised thick basement membrane
Podocytes of the Bowman’s capsule with their finger-like processes

Question 12

SO what gets filtered out of the blood in the glomerulus?

Answer 12

Anything that has a molecular weight of less than 55,000 - regardless of whether or not they are required in the blood

Question 13

What is the function of the proximal convoluted tubule?

Answer 13

Reabsorption - facilitated by Na+/K+ ATPase in the basolateral membranes

Question 14

What is reabsorbed in the proximal convoluted tubule?

Answer 14

Most of the water
Most of the Na+/Cl-
All of the amino acids
All of the glucose
Some bicarbonate HCO3-

Question 15

What is the function of the loop of Henle?

Answer 15

Creates and maintains the high ionic concentration of the medulla required for the control of urine concetration

Question 16

What are the two components of the loop of Henle and what are their functions?

Answer 16

Thick ascending limb:
Actively transports Na+/Cl- out of the tubule
Is impermeable to water
So the concentration of the medulla is becoming higher and lower in the tubule and a concentration gradient is established

Thinner descending limb:
SO due to the high water potential and osmotic pressure in the medulla, water is readily absorbed into the descending limb and is reabsorbed from the medulla, along with some Na+/Cl-

SO THIS SYSTEM ALLOWS for the reabsorption of water from the medulla which was lost at the glomerulus

Question 17

What is the function of the distal convoluted tubule?

Answer 17

Fine regulation of electrolyte and acid-base balance: Na+, K+, H+
Regulation ofl water balance involving ADH

Question 18

What is the juxtaglomerular apparatus?

Answer 18

Where the distal convoluted tubule bends back and meets the glomerulus

Question 19

What is the function of the juxtaglomerular apparatus?

Answer 19

Regulation of blood pressure and volume via the release of the enzyme renin

The Na+ concentration is sensed by the macula densa cells

Question 20

What is the function of the collecting duct?

Answer 20

Final concentration of urine - ADH sensitive

Electrolyte and acid-base balance - aldosterone sensitive