Renal 2

Question 1

Which parts of the kidney does the blood flow through during glomeluar filtration

Answer 1

During glomerular filtration blood flows into afferent arteriole then into the glomerulus.

Blood is filtered and the fluid and ion components pass across Bowman’s capsule into Bowman’s space.

Blood containing ions and molecules flows out of the glomerulus into the efferent arteriole then into the vasa recta.

Question 2

What are the 3 steps of glomeluar filtration

Answer 2

1. filtration
2. secretion
3. reabsorption

Question 3

What happens during the filtration step

Answer 3

During filtration ions and molecules move from blood plasma into Bowman’s space.
The afferent arteriole is wider than the efferent arteriole.
This results in increased pressure in glomerulus which aids filtration.

Question 4

What is the glomerular filtrate

Answer 4

Some fluid and molecules which are filtered out of the glomerulus and into Bowman’s space. These then flow along the nephron down into the renal pelvis to be excreted

Question 5

What happens in the secretion stage of glomeluar filtration

Answer 5

Secretion
Molecules are secreted from vasa recta peritubular capillaries into the tubules. Compounds within this secretion then pass along the tubules and can be excreted in the urine

Question 6

What happens in the reabsorption stage of glomeluar filtration

Answer 6

Molecules move from the tubular fluid into the vasa recta peritubular capillaries
These molecules then flow into the renal vein and so are reabsorbed from the tubular fluid back into the vasa recta capilliaries (so into the blood)

Question 7

What are the three layers the water, ions and drug molecules pass through whilst being filtered

Answer 7

Firstly they pass across the capillary endothelial cells.

Then they pass through a basement membrane to which the cells are attached.

Then they pass through a layer of podocyte cells and into Bowman’s space

Question 8

Why do we have pores in the capilliaries of the nephron

Answer 8

Pores in the capillaries act as a molecular sieve.

Pores allow molecules up to ~30 kDa in size to pass out of the capillary.

The plasma protein albumin is 69 kDa – so only ~0.005% is filtered in a healthy individual

Question 9

Why are some drugs filtered ineffectively by the kidneys

Answer 9

Some drugs are highly bound to plasma proteins

E.g. >95% warfarin is protein bound

A drug that is bound to plasma protein is unlikely to be filtered effectively

Question 10

What is the average plasma volume of a healthy adult and how many times per day is this plasma filtered through the kidneys

Answer 10

Plasma volume ~3 L

which is filtered 60-70 times/day

Question 11

What is the glomeluar filtration rate and why is it important to pharmacy

Answer 11

Glomerular Filtration Rate (GFR) is the rate at which plasma is filtered.

Its imporatant as its a key approach to assess how well the kidneys are functioning - by measuring the estimated Glomerular Filtration Rate (eGFR)

Question 12

How does the GFR work in the case of acute kidney injury

Answer 12

In Acute Kidney Injury there may be reduced blood flow to the glomerulus and reduced GFR
This means less drug enters the glomerulus and is filtered
So less drug is removed (cleared) from the plasma and renally excreted

Question 13

What is a common cause of chronic kidney disease

Answer 13

Chronic hypertension

Question 14

What are the characteristics of chronic hypertension and what do they lead to (in terms of kidney injury)

Answer 14

Characteristics of chronic hypertension include:

• thickening of blood vessels
• narrowing of the lumen
• less blood flow to kidney
• decrease in filtration

All these factors result in a decrease in GFR