Kidney Function 1 Flashcards

1
Q

What are the functions of the kidney?

A
  • water and sodium homeostasis
    • control of ion concentration
    • acid base balance
    • excretion of waste
    • endocrine
    • conserve or excrete water depending on conditions
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2
Q

What hormones are produced by the kidney?

A

EPO, renin, vitamin D3, PGI2

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3
Q

What are the two types of glomeruli?

A

superficial cortical glomeruli and juxtamedullary glomeruli

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4
Q

What percentage of glomeruli are superficial cortical glomeruli?

A

85%

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5
Q

What is the difference between SCG and JMG?

A

SCG have a short loop of Henle and are located in the outer cortex, JMG have a long loop and are located at the junction between cortex and medulla so their loop can penetrate deep into the medulla

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6
Q

What is the osmolarity of concentrated urine?

A

1200

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7
Q

What is the osmolarity of dilute urine?

A

300

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8
Q

What are the segments of the nephron?

A
  • bowman’s capsule
    • proximal tubule (convoluted tubule and pars recta)
    • thin descending loop of Henle
    • thin ascending loop of Henle
    • thick ascending loop of Henle
    • distal tubule
    • collecting duct
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9
Q

Where is most of the reabsorption done?

A

in the proximal tubule

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10
Q

Which part of the nephron is responsible for diluting urine?

A

thick ascending limb of Henle

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11
Q

Is there one collecting duct for every nephron?

A

no - a number of distal tubules converge on one collecting duct

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12
Q

What is the rate of renal blood flow?

A

1L/min

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13
Q

What is the filtration fraction?

A

0.2 - the amount of plasma that is filtered

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14
Q

What is the rate of renal plasma flow?

A

600mL/min

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15
Q

What is the GFR?

A

180L/day - amount of plasma filtered per day

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16
Q

What is the most important force that affects GFR?

A

Hydrostatic pressure in the glomerular capillary - this is why you need pre and post glomerular arterioles

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17
Q

Why isn’t all of the GFR excreted in urine?

A

because the peritubular capillaries reabsorb most of the filtrate

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18
Q

What happens to GFR with age?

A

it decreases

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19
Q

What is the amount of solute excreted equal to?

A

the amount filtered - the amount reabsorbed + the amount secreted

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20
Q

What is auto regulation?

A

the ability of renal blood flow to remain constant across a range of blood pressures (MAP 80mHg - 180mmHg)

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21
Q

What controls auto regulation?

A

tubular glomerular feedback and myogenic reflex

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22
Q

What is tubular glomerular feedback?

A

the macula densa in the thick ascending limb of the loop of Henle detects the amount of sodium chloride and there is a paracrine signal from the macula densa to the afferent arteriole to constrict with an increase in sodium chloride

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23
Q

What mediators send the paracrine signal from the macula densa to the afferent arteriole?

A

adenosine and thromboxane (vasoconstrictors) and prostaglandins (vasodilator)

24
Q

What is the myogenic reflex?

A

The ability of the afferent arteriole to constrict in response to stretch

25
Q

What is the purpose of auto regulation?

A

to keep the pressure in the glomerulus constant so that the filtration pressure is always 50mmHg

26
Q

What else is macula densa involved in?

A

renin release

27
Q

What is the function of renin?

A

increase blood pressure and conserve salt

28
Q

What causes renin release?

A

volume depletion and blood pressure decrease, sodium depletion (detected via macula densa), activation of sympathetic nervous system

29
Q

Where is renin released from?

A

granular cells of afferent arteriole

30
Q

What is the action of renin?

A

converts ANGI to ANGII

31
Q

What is the action of ANGII

A

many ways to increase blood pressure

32
Q

What is clearance?

A

the amount of plasma that is cleared of a solute per unit of time

33
Q

How do you calculate clearance?

A

UV/P where U is equal to the concentration in urine, V is the volume of urine and P is the plasma concentration

34
Q

What is creatinine clearance equal to?

A

GFR = 180L/day

35
Q

What would happen if GFR decreased?

A

creatinine concentration in the plasma would rise

36
Q

What is glucose clearance equal to?

A

0 - filtered freely but all is reabsorbed

37
Q

What happens if plasma glucose concentration is too high?

A

it saturates the active transport maximum so can’t all be reabsorbed and there is glucose in the urine

38
Q

What is penicillin clearance?

A

greater than GFR - because it is both filtered and secreted but not reabsorbed

39
Q

What must filtration pass through?

A

fenestrations of capillary walls, the basal lamina and filtration slits in foot processes of podocytes

40
Q

What are the limitations of what can be filtered?

A

size and charge - large molecules and negatively charged molecules are repelled

41
Q

Which plasma protein is highly negatively charged and therefore repelled?

A

albumin

42
Q

What does albumin in the urine indicate?

A

advanced diabetes - degeneration of basal lamina

43
Q

What is the hydrostatic pressure in the glomerular capillary?

A

50mmHg

44
Q

What is the hydrostatic pressure in Bowman’s capsule?

A

10mmHg

45
Q

What is the oncotic pressure in the glomerular capillary?

A

25-40mmHg - increases as filtration occurs

46
Q

What is the oncotic pressure in Bowman’s capsule?

A

0mmHg

47
Q

What is the net filtration pressure?

A

15mmHg

48
Q

What stops filtration from occurring at the end of the capsule?

A

the increase in oncotic pressure in the glomerular capillary

49
Q

What happens to GFR with constriction of the afferent arteriole?

A

GFR will decrease - reduce the flow so reduce the pressure so reduce the GFR

50
Q

What happens to GFR with constriction of the efferent arteriole?

A

GFR will increase - bank up blood will increase pressure so increase GFR

51
Q

Which arteriole does angiotensin II preferentially constrict?

A

the efferent arteriole - therefore leads to an increase in GFR

52
Q

What will constrict the afferent arteriole?

A

noradrenaline (sympathetic nervous system) - trying to maintain BP and will sacrifice blood flow to the kidney to ensure the blood flow to the brain is maintained - but will hopefully be balanced out by RAAS

53
Q

What makes up the juxtaglomerular apparatus?

A

macula densa cells, granular cells and the mesangial cells

54
Q

What is the function of mesangial cells?

A

provide structure and constrict the glomerular capillaries to alter glomerular filtration by altering capillary surface area

55
Q

How is the pressure in Bowman’s capsule increased?

A

blocking the outflow e.g. kidney stones or benign prostatic hypertrophy - the result will be a decrease in GFR