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[Y1] Anatomy and Physiology > *The renal system > Flashcards

*The renal system Flashcards

1
Q

how much water does the NHS say to drink per day?

A

1.6L

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2
Q

what is excreted by the kidneys?

A

water, urea (protein break down), H+, water soluble waste

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3
Q

what does the urinary system consist of?

A
  • 2 kindeys
  • 2 ureters
  • 1 urinary bladder
  • 1 urethra
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4
Q

what are the 4 functions of the kidneys?

A
  • Excretion of waste products (filters blood)
  • Formation of urine, maintaining water, electrolyte and acid-base balance
  • Production and secretion of erythropoietin (RBC synthesis)
  • Production and secretion of renin (BP regulation)
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5
Q

what is the function of the bladder?

A

stores urine ready for excretion by micturation

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6
Q

how much urine do the kidneys produce per day?

A

~1.5 L

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7
Q

what is the primary function of the kidneys?

A

maintain the constancy of the internal environment i.e. homeostasis

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8
Q

which kidney is lower than the other? why?

A

right is slightly lower than left (due to liver)

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9
Q

where do the adrenal glands sit?

A

on top of the kidneys

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10
Q

what is the function of the ureters?

A

drain urine from the kidneys to the bladder

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11
Q

how much urine can the bladder hold?

A

<600ml

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12
Q

what is the urethra?

A

tube from the bladder to exterior

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13
Q

is the urethra shorter in males or females?

A

females

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14
Q

how long, wide and thick are the kidneys?

A

-11cm long
- 6cm wide
- 3cm thick

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15
Q

what is the approx. weght of a kidney?

A

150g

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16
Q

what is the hilum?

A

the concave medial border where everything enters / exits

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17
Q

what is the renal pelvis?

A

where the urine collects

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18
Q

what are the 3 layers to the kidneys?

A
  • the capsule (fibrous outer layer)
  • the cortex (reddish brown smooth looking)
  • the medulla (Innermost layer, conical-shaped striations (the renal pyramids))
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19
Q

what is the functional uniit of the kidneys?

A

1 million nephrons

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20
Q

where is the blood filtered and urine formed in the kidneys

A

nephrons

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21
Q

what is a nephron?

A

A blind ended tube that drains into a collecting duct

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22
Q

what is the basement membrane in the kidneys?

A

porous negatively charged glycoproteins, main site of filtration of proteins q

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23
Q

what lines the glomerular capsule? why?

A
  • podocytes
  • prevents large molecules from leaving the blood
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24
Q

what are the 2 types of nephrons? what percentage in the body?

A
  • 80-85% nephrons are cortical nephrons
  • 15-20% nephrons are longer juxtamedullary nephrons
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25
Q

what is the function of hte longer tubule in juxtamedullary nephrons?

A

enables us to concentrate urine

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26
Q

why does the number of nephrons remain constant from birth?

A
  • growth is by growth in size not by growth in numbers
  • nephrons not replaced
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27
Q

how much of the cardiac output goes to the kidneys?

A

about 20%

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28
Q

where does the renal artery enter? what happens?

A

enters the kindeys. at the hilum and divides into smller arteries and arterioles

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29
Q

what do the afferent aterioles do?

A

enters each glomerulus and subdivides into tiny capillaries (the glomerulus)

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30
Q

what do the efferent arterioles do?

A

leaves the glomerulus.

31
Q

which type of arterioles have a larger diameter in the kidneys?

A

Afferent arterioles have a larger diameter than efferent arterioles. (to drive filtration)

32
Q

what 3 factors affect the resistance to flow of fluids?

A
  • diameter of tube
  • length of tube
  • viscosity of fluid
33
Q

what does reducing the diameter do to the resistance?

A

increases resistance (and pressure)

34
Q

what is the approx. pH of urine?

A

~pH6

35
Q

what percentage of urine is urea?

A

2%

36
Q

what percentage of urine is water?

A

96%

37
Q

is urine hypotonic or hypertonic to plasma?

A

hypertonic

38
Q

how much HCO3^-1 is in urine?

A

0mM

39
Q

how much phosphate is in urine?

A

25-60mM

40
Q

how much creatinine is in urine?

A

6-20mM

41
Q

how much urea is in urine?

A

200-400mM

42
Q

how much NH4^+1 is in urine?

A

30-50mM

43
Q

how much protein is in urine?

A

0 g/L

44
Q

how much glucose is in urine?

A

0mM

45
Q

what is the osmolarity of urine?

A

50-1300. mOsm/Kg

46
Q

what are the 3 processes involved in the formation of urine?

A
  • filtration (out of blood)
  • selective reabsorbtion (into blood)
  • tubular secretion (out of blood)
47
Q

what does the composition of urine reflect?

A

the exchange of substances between the nephron and renal capillaries.

48
Q

explain filtration in the kidneys?

A

Filtration takes place through the semipermeable walls of the glomerulus and glomerular capsule.

49
Q

what molecules can pass through in filtration and which can’t?

A
  • Water and small molecules (<5000Da) pass through easily (some reabsorbed later)
  • Large molecules (>5000Da eg. proteins) and the blood cells stay in capillaries.
50
Q

what are the 3 steps to the filtration membrane?

A
  1. Capillary endothelium: pores (fenestrations) increase permeability (endothelium is normally a barrier)
  2. Basement membrane: porous negatively charged glycoproteins, main site of filtration of proteins
  3. Bowman’s capsule lined by podocytes that only allow small things passed
51
Q

what does fitration depend upon?

A

a pressure difference

52
Q

what are the 4 pressures that affect filtration in the kidneys?

A
  • Glomerular hydrostatic pressure (pushing) is higher
  • Osmotic pressure is the pull of water into the capillaries
  • Filtrate hydrostatic pressure is the push of water
  • A positive net filtration pressure creates urine
53
Q

what is the glomerular filtration rate?

A

Glomerular filtration rate (GFR) is the volume of filtrate formed by both kidneys each minute.

54
Q

what is the GFR in a healthy human adult?

A

~125ml/min

55
Q

what is autoregulation in filtration?

A

Autoregulation is the mechanism of maintaining a constant renal blood pressure (vasoconstriction/ dilation of afferent arteriole) in order to protect (maintain) the GFR.

56
Q

the capillaries reabsorb __% of the filtrate

A

99%

57
Q

what is most of the reabsorbtion carried out by?

A

the proxmal tubules (increased surface area with microvilli)

58
Q

how are solutes reabsorbed in selective reabsorbtion?

A

active and passive transport

59
Q

what 2 things are almost completely reabsorbed? when are they excreted?

A
  • glucose and amino acids
  • unless blood levels are excessive
60
Q

what is obligatory reabsorbtion?

A

water follows solutes by osmosis

61
Q

what waste products are not reabsorbed?

A

nitrogenous waste products

62
Q

what is the renal threshold?

A
  • The renal threshold or transport maximum is the maximum capacity the kidneys have for reabsorbing a substance
  • If a substance rises above the renal threshold it will appear in the urine.
63
Q

what is tubular secretion?

A

Transfer of substances (not cleared by filtration in the glomerulus) from the peritubular capillaries into tubular fluid

64
Q

what 2 things does tubular secretion help with?

A
  • Helps control blood pH because of secretion of H+
  • Helps eliminate certain substances (NH4+, creatinine, K+, some drugs including penicillin, aspirin) including large molecules
65
Q

state 5 things about the proximal tubule and decending loop

A
  • Highly permeable to water and solutes (most reabsorption occurs here)
  • Na+/K+ ATPase sets up sodium gradient to resorb Na+
  • ‘leaky’ tight junctions allow water and K+ to be reabsorbed paracellularly (between cells)
  • Glucose and amino acids ~100% reabsorbed by facilitated diffusion into ISF (Na+-coupled)
  • Bicarbonate moves into ISF by HCO3-/Cl- exchange
66
Q

state 2 things about the ascending loop

A
  • Highly permeable to NaCl but not water (tight junctions)
  • Na+/K+ ATPase sets up sodium gradient to reabsorb Na+
67
Q

what does aldosterone act on in the kidneys?

A

acts on Principle (P) cells to secrete K+ / reabsorb Na+ (water follws)

68
Q

what are the collecting ducts permeable to? what is it regulated by?

A

Permeable to water and urea, regulated by hormones (ADH)

69
Q

what increases water and urea permeability?

A

aquaporins

70
Q

what are 3 common measures to measure renal function?

A
  • clearance rate
  • glomerular filtration rate (GFR)
  • Plasma flow rate (PFR)
71
Q

what is the equation for clearance rates?

A

clearance = (UxV) / P
where:
U= urine concentration of substance x (in mg/ml)
V = the rate of urine production in ml/min (from 24h collection)
P = plasma concentration of substance x (in mg/ml)

72
Q

why does insulin clearance = GFR?

A

insulin is freely filtered and not reabsorbed or secreted

73
Q
A

[Y1] Anatomy and Physiology (23 decks)

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