urinary system 1

Question 1

urinary excretion - kidney to bladder
3 processes

Answer 1

1. glomerular filtration
2. tubular secretion
3. tubular reabsorption

Question 2

glomerular filtration

Answer 2

• glomerulus to capsular space
• bowmans space : inside glamarular capsule

Question 3

tubular reabsorption

Answer 3

-tubular lumen to peritubular capillary

-peri= around peritubular= around capillary

Question 4

tubular secretion

Answer 4

peritubular capillaries to tubular lumen

Question 5

what processes make excretion

Answer 5

excretion = filtered + secreted - reabsorbed

-can alter the balance of 3 process to alter excretion

Question 6

3 examples how to alter excretion

Answer 6

x : harmful substance or waste

y: useful substance; being regulated. most common

z : important substance for health, no excretion. nothing in urine

glucose in urine not normal, associated with diabetes

Question 7

glomerular filtration

Answer 7

-kidneys try to maintain a relatively constant GFR

-1st chance to eliminate substance

-strong homeostatic mechanisms

Question 8

glamarular filtration rate (GFR) (mL/min)

Answer 8

too high - substances pass too quickly and are not adequately reabsorbed

(better kidney function)

too low - nearly all substances reabsorbed and some waste products not adequately eliminated

(kidneys not working very well)

Question 9

afferent arteriole

Answer 9

blood coming into glamurulus

Question 10

efferent arteriole

Answer 10

blood coming out of glamarular

Question 11

tubular reabsorption

Answer 11

• tubular lumen to peritubular capillaries
• mechanism for retaining substances
• proximal tubule largest contribution to reabsorption; fine-tuning further along tubules

Question 12

tubular secretion

Answer 12

• peritubular capillaries to tubular lumen
• 2nd chance to eliminate substance after filtration (GFR)
• mechanism for eliminating undesired substances or end-products/removing excesses/ controlling blood acid-base balance

Question 13

apical membrane

Answer 13

borders tubular lumen

Question 14

basolateral membranes

Answer 14

borders tubular epithelial cell

Question 15

glomerulus more or less efficient than other capillary beds at filtration?

Answer 15

more efficient

-180L/day in glomerulus vs. 4 L/day in systemic capillary beds

Question 16

glomerular filtration membrane

Answer 16

• large surface area
• very permeable (with pores; 45 x leakier than typical capillary bed)
• glomerulus blood pressure is higher than blood pressure in systemic capillaries (60 mmHg vs. 15-35 mmHg)

Question 17

glomerular filtrate

Answer 17

volume of fluid becoming filtrate (litres ~ 150-180 L in a day)

Question 18

filtration fraction

Answer 18

fraction of fluid becoming filtrate (typical is 20%)

Question 19

glomerular filtration rate (GFR)

Answer 19

amount of filtrate formed by both kidneys each minute (L/min; typical is 125 mL/min)

Question 20

principle of filtration

Answer 20

force fluids and substances through a membrane by pressure

Question 21

starling forces of net filtration pressure in glomerulus

Answer 21

Net glomerular filtration pressure = Pgc - Pbs - pi gc

Pgc = pressure of glomerular capillary blood (60)

Pbs= pressure of fluid in bowman’s space (15)

pi gc= osmotic force due to protein in plasma (29)

• 2 hydrostatic (away from itself) and 2 osmotic (toward itself)
• usually 1 osmotic left out because it is = 0 (osmotic force of the fluid)
• forces favour filtration over entire length
• healthy kidney will produce positive number
• 20% leaves bloodstream in glomerulus as glomerular filtrate

Question 22

renal autoregulation

Answer 22

intrinsic mechanism within kidneys (doesnt require outside forces)

• protects the kidneys from elevated arterial pressure that would effect kidney
• blunts direct effects that changes in arterial pressure would otherwise have on GFR
• within a wide autoregulatory range can compensate for arterial pressure changes

autoregulation : keeping us in this homeostatic state

Question 23

(renal autoregulation)

myogenic mechanism

Answer 23

-seconds

• smooth muscles in arterioles respond to changing systemic blood pressure
• alter vessel diameter / alter Pgc / alters NFP / alters GFR

Question 24

2nd mechanism - tubuloglomerular feedback

Answer 24

• a little slower to respond than myogenic
• detect changes in sodium, chloride, water
• alter release of vasodilator nitric oxide (NO)

less nitric oxide = vasoconstrictor of afferent arteriole = decrease GFR

Question 25

less nitric oxide

Answer 25

vasoconstrictor of afferent arteriole = decrease GFR

Question 26

glomerular filtration rate - neural regulation

Answer 26

Neural regulation :

• extrinsic mechanism outside kidney
• can over ride autoregulation, must be strong effect
• kidneys richly supplied by sympathetic that release norepinephrine and vasoconstrict afferent arterioles
• -increase sympathetic stimulation (decrease GFR)*
• -decrease sympathetic stimulation (increase GFR)*

direct effect : arterial blood pressure directly effects GFR

Question 27

angiotensin 2

Answer 27

• vasoconstricts afferent and efferent arterioles
• greater effect on afferent so decrease GFR

Question 28

atrial natriuretic peptide (ANP)

Answer 28

• vasodilates afferent arterioles and vasoconstricts efferent arterioles
• increases capillary surface of glomerulus by relaxing mesangial cells
• both will increase GFR

Question 29

hormonal regulation

Answer 29

• extrinsic mechanism outside kidney
• can over ride autoregulation, but must be strong effect