Renal physiology

Question 1

What are the functions of the renal system?

Answer 1

Regulation of water, ions, acid-base; removal of metabolic waste products from blood (urea and creatine); removal of foreign chemicals fro the blood; gluconeogenesis during prolonged fasting; production of hormones/ enzymes

Question 2

What hormones/enzymes does the renal system produce?

Answer 2

Erythroprotein, controls RBC production; renin, controls formation of angiotensin; conversion of 25-hydroxyvitamin D –> 1,25-dihydroxyvitamin D, influences Ca2+ balance

Question 3

What are the two (VERY GENERAL) sections of the nephron?

Answer 3

Renal corpuscle and tubule

Question 4

How much of plasma is filtered into Bowman’s?

Answer 4

~20%

Question 5

How is the glomerulus/Bowman’s capsule specialised for its function?

Answer 5

Has arterial afferent and efferent flow, creating high blood pressure; very porous glomerulus to allow fluid and other ions to be squeezed out of blood; podocytes with slite allow additional filtration

Question 6

What is in the filtrate that enters the Bowman’s space?

Answer 6

Na+, Cl-, K+, H2O, glucose, amino acids

Question 7

What occurs at the proximal convoluted tubule?

Answer 7

Reabsorption by active transport; Na+, glucose, small H2O

Question 8

What occurs at the Loop of Henle?

Answer 8

Na+, K+ and Cl- reabsorbed at ascending limb by active transport; medulla becomes hypertonic; water leaves descending limb down water potential gradient

Question 9

What occurs at the distal convoluted tubule?

Answer 9

Further reabsorption occurs

Question 10

What occurs at the collecting duct?

Answer 10

ADH acts to allow more water to be reabsorbed by mobilisation of aquaporins

Question 11

What parts of the nephron are within the medulla?

Answer 11

Glomerulus, Bowman’s capsule, PCT, some of Loop of Henle, DCT, some of collecting duct

Question 12

What parts of the nephron are within the cortex?

Answer 12

Some of Loop of Henle and collecting duct

Question 13

What are the three basic process of the nephron?

Answer 13

Glomerular filtration, tubular secretion, tubular reabsorption

Question 14

How does the kidney differentially handle substances?

Answer 14

Depending on necessity to body, may be fully excreted, partially, or fully reabsorbed

Question 15

How is the amount excreted by the kidneys calculated?

Answer 15

Amount filtered + amount secreted - amount reabsorbed

Question 16

Why do plasma proteins remain in plasma?

Answer 16

To maintain osmotic pressure

Question 17

What disease is kidney damage often found in?

Answer 17

Diabetes and hypertension. If left untreated, can lead to end-stage renal disease and renal failure

Question 18

What is glomerular filtration governed by?

Answer 18

Starling’s forces: hydrostatic pressure difference vs protein concentration difference (filtration vs osmotic force). Thus can be controlled by vascular changes

Question 19

What is tubular reabsorption?

Answer 19

Can be active or passive; paracellular transport occurs b/w cells; mostly seen with ions; begins as soon as filtrate enters tubule cells

Question 20

What is tubular secretion?

Answer 20

H+, K+ or organic ions from peritubular capillaries into tubular lumen; important mechanism for disposal of drugs and drug metabolite/ undesired substances or end products that have to reabsorbed by passive process (urea, uric acid)/ excess K+/ controlling blood pH

Question 21

What is renal clearance?

Answer 21

Volume of plasma that is cleared of a substance in one minute

Question 22

What is the equation for renal clearance?

Answer 22

([substance] in urine*flow rate of urine formation)/[substance] in plasma

Question 23

How can renal clearance be measured?

Answer 23

Insulin as is freely filtered, not reabsorbed or secreted; creatinine is less accurate as secreted in small amounts