Renal phys- function, filtration, reabsorption & secretion NOT DONE

Question 1

What are the 7 key functions of the kidneys? List

Answer 1

1) Excretion of metabolic waste products
2) regulation of water & electrolytes
3) regulation of arterial pressure
4) acid-based balance
5) regulate RBC production
6) Vitamin D activation
7) Gluconeogenesis

Question 2

Regulation of water and electrolyte balances: How do we concentrate urine? Can filtration be manipulated?

Answer 2

Water is excreted into surrounding tissues when if the body is dehydrated (by anti-diuretic hormone), making the urine more concentrated. If the body is hydrated enough, then the kidneys will retain the water with the urine and the urine will not be as concentrated.
Diuretics: can mask substances in the urine e.g. drugs

Question 3

What is filtration?

Answer 3

Where fluid leaves plasma in the glomerulus and enters Bowman’s space.

Question 4

What is glomerular filtration rate- GRF

Answer 4

volume of fluid filtered into Bowman’s capsules per unit of time

Question 5

Explain hydrostatic pressure in the kidneys (in relation to blood flow and glomerular capillaries)

Answer 5

Large hydrostatic pressure in short, straight arterioles
Hydrostatic gradient favours outflow of fluids
High resistance, maintains hydrostatic pressure in glomerulus

Question 6

What is meant by starling’s forces? Relate it to hydrostatic and oncotic pressure

Answer 6

Hydrostatic and oncotic pressures together form starlings forces - govern filtration in the kidneys (opposing forces)

• Hydrostatic pressure: forces fluids OUT into Bowman’s space
• Oncotic pressure: RETAINS fluid in capillaries

Question 7

**What factors determine filtration? (3 factors) (list them)

Answer 7

1) hydrostatic pressure (fluid pressure)
2) osmotic pressure (due to proteins)
3) physical properties of glomerular capillaries (filtration)

Question 8

Discuss osmotic pressure in kidneys (in relation to blood flow and glomerular capillaries)

Answer 8

Osmotic gradient favours inflow of fluids, this decreases the glomerular filtration rate is protein is in great quantities (more fluid flowing in counteracting the hydrostatic pressure of fluid flowing out)

Question 9

Where does the fluid go to in filtration?

Answer 9

Where fluid leaves plasma in the glomerulus and enters Bowman’s space.

Question 10

List the 7 key functions of the kidneys?

Answer 10

1) Excretion of metabolic waste
2) regulation of water and electrolytes
3) regulation of arterial pressure
4) acid-based balance
5) regulate RBC production
6) vitamin D activation
7) gluconeogenesis

Question 11

Regulation of water and electrolyte balances: how do we concentrate urine? can filtration be manipulated?

Answer 11

Water is excreted into surrounding tissues if the body is dehydrated (by anti-diuretic hormone), making urine more concentrated. If body is hydrated enough, then the kidneys will retain the water with the urine and the urine will not be as concentrated.

Diuretics: can mask substances in urine e.g. drugs.

Question 12

what effects oncotic pressure?

Answer 12

protein levels – low or high protein will generate oncotic pressure (up-taking fluid from Bowman’s space to dilute protein, or reduce oncotic pressure)

Question 13

**Discuss the transport maximum of sodium in relation to carrying high levels of glucose (related to reabsorption- tubular maximum)

Answer 13

add more*

sodium gradient used to transport things across for reabsorption

glucose reabsorption - how can we max out? – transport proteins maxed out if glucose levels are really high

Question 14

What percentage of filtrate reabsorbed in PCT

Answer 14

65% in PCT

15% in loop of henle

15% in distal tubule DT

5% in CD

Question 15

Discuss what substances are reabsorbed/and not reabsorbed

Answer 15

• foreign substances poorly reabsorbed and are secreted
• electrolytes reabsorbed
• nutritional substances completely reabsorbed

Question 16

**what parts are permeable to water within the nephron

Question 17

renal clearance of a substance is determined by (3 things)

Question 18

*what is a substance that is freely filtered and not reabsorbed or secreted by renal tubules?

Answer 18

Inulin- naturally occurring polysaccharides

• provides true estimate of filtration as there is no reabsorption or secretion of inulin*

Question 19

There can be 3 causes of decreased GFR that aren’t just renal disease. What are these?

Answer 19

1) prerenal - dehydration etc.
- will retain water, thus high USG (concentrated urine)
2) renal - kidney dysfunction
- low usg as kidneys will not be concentrating the urine due to damage
3) postrenal - urinary calculi causing a blockage
- probably blocked and no urine, so low USG as urine won’t be processing/being filtered

Question 20

What does USG test for in urinalysis? If dog is dehydrated (pre-renal), will usg be high or low?

Answer 20

Urine specific gravity - basically tests for how concentrated the urine is in comparison to filtered water.

USG will be high as the urine will be concentrated as body is retaining water.

Question 21

Regulation of water and electrolyte balances: how do we concentrate urine? can filtration be manipulated?

Answer 21

Water is excreted into surrounding tissues if the body is dehydrated (by anti-diuretic hormone), making urine more concentrated. If body is hydrated enough, then the kidneys will retain the water with the urine and the urine will not be as concentrated.

Diuretics: can mask substances in urine e.g. drugs.