2. Glomerulus

Question 1

What is osmolality?

Answer 1

Solute per kg of solvent

Question 2

What is osmolarity?

Answer 2

Number of osmoles of solute per litre

Question 3

Where is the glomerulus found?

Answer 3

Only in the cortex

Question 4

What is the normal total glomerular filtrate per day?

Answer 4

140-180L/day

Question 5

How do you work out the filtration fraction?

Answer 5

GFR/RPF (renal plasma flow)

Question 6

What is renal plasma flow?

Answer 6

800ml/min

Question 7

What is a normal GFR?

Answer 7

90-120ml/min/1.73m^2

Question 8

What are the layers of the glomerular capillary membrane?

Answer 8

Fenestration between endothelial cells
Basement membrane
Filtration slit
Podocyte processes
Podocyte cell body (Bowman’s capsule epithelium)
Bowman’s space

Question 9

What causes filtration to occur?

Answer 9

Mainly hydrostatic pressure in capillary

Hydrostatic pressure of Bowman’s capsule and oncotic pressure pushes water back into capillaries

Question 10

What are the 2 mechanisms involved in autoregulation of renal blood flow and GFR?

Answer 10

Myogenic mechanism

Tubuloglomerular feedback

Question 11

How can you cause a decrease in GFR?

Answer 11

Myogenic response

Constrict afferent arteriole or dilate efferent arteriole

Question 12

How can you cause an increase in GFR?

Answer 12

Myogenic mechanism

Construct efferent arteriole or dilate the afferent arteriole

Question 13

What is tubuloglomerular feedback?

Answer 13

Links sodium and chloride concentration at the macula densa with control of renal arteriolar resistance
Acts in response to acute perturbations in delivery of fluid and solutes to JGA (juxtaglomerular apparatus)
Controls distal solute delivery and hence tubular absorption

Question 14

How does tubuloglomerular feedback work?

Answer 14

Macular densa cells of DCT epithelium detect osmolality of rate of movement of Na or Cl into cells
Signal sent via juxtaglomerular cells, triggered by increase in NaCL conc of distal tubular fluid
Further vasoconstriction of smooth muscle of adjacent afferent arterioles and therefore reduced RPF and reduced GFR

Question 15

What happens with the tubuloglomerular feedback mechanism with low BP?

Answer 15

Release of prostaglandins - attenuate construction of afferent arteriole
Renin released by juxtaglomerular cells due to sympathetic nerve stimulation, less stretch of afferent arteriole, signals generated by may all densa cells

Question 16

What is the role of renin?

Answer 16

Allows conversion of angiotensin to angiotensin 1, then to angiotensin 2, which constricts efferent arterioles and increases GFR