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Human Physiology Y3 > Function of the Kidney > Flashcards

Function of the Kidney Flashcards

1
Q

What does the kidney excrete?

A

Metabolic waste products and foreign chemicals

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2
Q

What production does the kidney regulate?

A

Red blood cell production

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3
Q

What does the kidney keep in balance?

A

Regulates acid-base balance
Water & electrolyte balance

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4
Q

What pressure does the kidney regulate?

A

Arterial pressure

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5
Q

What part of body fluids does kidney regulate?

A

Body fluid osmolality
Electrolyte concentration

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6
Q

What hormone does the kidney synthesise?

A

Calcitriol

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7
Q

What are the 5 symptoms of kidney impairment?

A
  1. Body weakness
  2. Blood pressure is high
  3. Swollen legs
  4. Loss of appetite
  5. Vomiting
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8
Q

What abnormal levels of ions can affect the heart in kidney impairment?

A

High K+
Low Ca2+

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9
Q

What is a xenotransplant?

A

A transplant from a donor of a different species from the recipient

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10
Q

What does the ureter lead from and to?

A

From kidney to urinary bladder

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11
Q

What is the role of the urethra?

A

Urine stored in the bladder is emptied through the urethra

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12
Q

How many lobes does a kidney have and what are they composed of?

A

18 lobes composed of nephrons

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13
Q

What is the outer layer of the kidney called?

A

Renal cortex = granular apprearing

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14
Q

What is the inner layer of the kidney called?

A

Renal medulla = striated-appearing

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15
Q

What is the role of the renal pelvis?

A

Collects the urine as it is produced

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16
Q

What does the renal pelvis lie outside of?

A

Peritoneal cavity

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17
Q

What is the flow of urine through the calyxes?

A

Renal pyramid > Renal Papillae > Minor renal calyx > Major renal calyx > Renal pelvis

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18
Q

What happens to nephrons when damaged?

A

Nephrons cannot be regenerated
Treatment can only try to preserve what is remaining

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19
Q

What two layers separate the blood from the glomerular filtrate?

A

Capillary endothelium
Specialized epithelium of Bowman’s capsule

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20
Q

Describe the capillary endothelium

A

Endothelium is fenestrated = has small pores
Completely surrounded by glomerular basement membrane and podocytes
Podocytes create filtration slits

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21
Q

What are podocytes?

A

Bowman’s capsule cells that have foot processes
They interact with each other to forma mesh-like structure

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22
Q

Where are mesangial cells located?

A

Between endothelium and glomerular basement membrane (basal lamina)

Commonly found between two neighbouring capillaries

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23
Q

What do mesangial cells do?

A

Regulate blood flow in glomerulus

By regulating the surface area available for filtration by contracting or relaxing in response to various signals

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24
Q

What does the juxtaglomerular complex consist of?

A

Macula densa
Juxtaglomerular cells

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25
Q

What and where are macula densa and their role?

A

Tubule cells in initial portion of the distal tubule

They act as chemoreceptors, sensing changes in NaCl concentration in the tubular fluid

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26
Q

What are juxtaglomerular cells and their function?

A

Special cells of the blood vessel walls
Blood vessels = afferent and efferent arterioles

Produce and release the enzyme renin = primary function

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27
Q

What is the function of the juxtaglomerular complex?

A

Regulate blood pressure, Na reabsorption and glomerular filtration
Synthesize renin

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28
Q

What are the two types of nephron?

A

Cortical nephron = 85%
Juxtamedullary nephron = 15%

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29
Q

Describe the cortical nephron

A

Short loop of Henle
Small network of vasa recta

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30
Q

Describe the juxtamedullary nephron

A

Long loop of Henle = reaches medulla
Large network of vasa recta

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31
Q

What role does the juxtamedullary nephron play?

A

Concentrating and diluting urine

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32
Q

What is the vasa recta and their role?

A

Network of blood vessels that run parallel to the loops of Henle in the kidney medulla = arise from the efferent arterioles

Supply oxygen and nutrients to the medullary tissue while also removing waste products

Crucial role in maintaining the osmotic gradient in the medulla, which is essential for the kidney’s ability to concentrate urine

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33
Q

What percentage is renal blood flow in relation to cardiac output?

A

22% of CO = 1,100 mL/min

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34
Q

What capillary beds does the renal circulation have?

A

Glomerular capillaries = starts and ends as arteriole
Peritubular capillaries = starts as artery ends as venule

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35
Q

Location: glomerular vs peritubular capillaries

A

Glomerular = found within glomerulus
Peritubular = surround the renal tubules in the kidney cortex and medulla

36
Q

Function: glomerular vs peritubular capillaries

A

Glomerular = specialized for filtration
Peritubular = involved in reabsorption and secretion

37
Q

What is the GFR per day?

A

180L/day

38
Q

What is the approximate urine volume?

A

1 - 1.5 L per day

39
Q

What is excretion a sum of?

A

Excretion = glomerular filtration + tubular secretion - tubular reabsorption

40
Q

What are the 4 methods of renal handling of substances?

A
  1. Filtration only
  2. Filtration and partial reabsorption
  3. Filtration and complete reabsorption
  4. Filtration and secretion
41
Q

What substances are filtered only?

A

Inulin

42
Q

What substances are filtered and partially reabsorbed?

A

Many electrolytes = Na, Cl

43
Q

What substances are filtered and fully reabsorbed?

A

Amino acids and glucose

44
Q

What substance are filtered then secreted?

A

Creatinine and certain drugs

45
Q

What is tubular secretion?

A

Vital mechanism by which the kidneys selectively remove substances from the bloodstream and excrete them in the urine, contributing to the regulation of body fluid composition and overall homeostasis.

46
Q

What is creatinine?

A

Waste product generated by the breakdown of creatine phosphate in muscles

47
Q

What does tubular secretion regulate?

A

K+ and H+

48
Q

What is the GFR per minute?

A

Volume of plasma ultrafiltrate formed each minute 125 mL/min

Slightly lower in females

49
Q

What is renal plasma flow?

A

Amount of plasma that is delivered to the kidneys for filtration and processing = crucial to assess kidney function and renal blood flow

625 mL/min

50
Q

Filtration fraction equation

A

Glomerular Filtration Rate / Renal Plasma Flow = 125 / 625 = 0.2

20% of plasma flowing though kidneys = filtered through the glomerular capillaries

51
Q

What factors determines the GFR?

A

Surface area of capillary bed

Permeability of capillaries

Hydrostatic and osmotic pressure gradient across capillary wall

52
Q

Glomerular ultrafiltration coefficient (Kf)

A

Kf = glomerular capillary permeability x filtration surface area

53
Q

How does capillary bed surface area affect GFR?

A

Angiotensin II = vasoconstrictor
Contraction of mesangial cells = reduces area available for filtration
Changes diameter of blood vessels

54
Q

What is special about glomerular capillaries?

A

More permeable than other capillary beds

55
Q

What is the rule about filtration based on permeability?

A

Molecules less than 4nm = freely filtered

Intermediate size molecules filtered depending on CHARGE

The basal lamina = negative
So positive particles are readily filtered

56
Q

What is capillary permeability for proteins?

A

Largely impermeable to protein

57
Q

Example of a small plasma protein not being filtered

A

Albumin repelled because it is negatively charged so not filtered even though it is small

58
Q

What happens in glomerulonephtitis?

A

Immune cells attack and damage glomerulus
Glomerular negative charge lost
Albumin can then enter urine

59
Q

Define glomerular hydrostatic pressure

A

Pressure from blood in glomerular capillary wanting to enter nephron

Favours filtration = +55mmHg

60
Q

Define colloid osmotic pressure

A

Proteins attracting water out of nephron

Opposes filtration = -30 mmHg

61
Q

Define Bowman’s hydrostatic pressure

A

Pressure from fluids in capillaries against Bowman’s capsule
Opposes filtration = -15mmHg

62
Q

What is the net filtration pressure?

A

Favours filtration = +10 mmHg
Difference between

63
Q

What is the difference between gomerular capillaries and normal capillaries?

A

Glomerular capillaries = high pressure system
Others = low pressure system

64
Q

What factors cause a decrease in GFR?

A

Age, Renal disease, Diabetes mellitus, hypertension, decrease in Kf

65
Q

Difference in diameter of arterioles?

A

Afferent arterioles = smaller than efferent
Creates bottle-neck effect

66
Q

What happens to GFR if there is in obstruction of the urinary tract?

A

Increase in Bowman’s capsule hydrostatic pressure = decrease GFR

67
Q

What happens to GFR when sympathetic activity increases?

A

Increase sympathetic activity = increase vasoconstrictor hormones

Afferent arteriolar constriction

Reduce renal blood flow
Reduce glomerular hydrostatic pressure

Reduce GFR

68
Q

What does increased Angiotenin II do to GFR?

A

Efferent arteriolar constriction = INCREASE GFR

Also causes mesangial contraction = reduction in GFR
BUT, the strong effect on efferent arteriole usually leads to the effect of overall increase in GFR

69
Q

What effect does artieral pressure have on GFR?

A

Minimal affect since renal blood flow is autoregulated

70
Q

What effect does high salt and protein intake have on GFR?

A

Increases GFR

71
Q

How is renal blood flow autoregulated?

A

Myogenic mechanism and tubuloglomerular feeback

72
Q

How does the myogenic mechanism work?

A

Muscle reflex to adjust blood flow into the kidneys based on changes in blood pressure = adjusts to stretch

73
Q

What is tubuloglomerular feedback?

A

Feedback mechanism that links changes in NaCl conc at macula densa to renal arteriolar resisance and autoregulation of GFR

74
Q

What do macula densa monitor?

A

NaCl concentration = part of tubuloglomerular feedback

75
Q

What happens to afferent arteriolar resistance when arterial presure decreases?

A

Glomerular hydrostatic presure decreases -> GFR decreases -> Decrease in macula densa NaCl -> Decrease afferent arteriolar resistance

76
Q

What happens to efferent arteriolar resistance when arterial pressure decreases?

A

Senses decrease in NaCl -> Increases renin -> Increases Angiotensin II leading to increase in efferent arteriolar resistance [ THIS IS TO MAINTAIN GFR ]

77
Q

What is renal plasma clearance?

A

Voume of plasma that is completely cleared of a substance by the kidneys per unit of time. It represents the efficiency with which the kidneys remove a particular substance from the bloodstream through filtration and/or secretion

78
Q

Units of renal plasma clearance

A

mL per min

79
Q

How to calculate clearance rate?

A

Conc of substance in urine / concentration of substance in blood

80
Q

When does the clearance of the substance = GFR?

A

For substances that are only filtered (not reabsorbed or secreted)

81
Q

How do you calculate urine flow rate?

A

Urine volume / time in minutes

82
Q

How to calculate GFR?

A

(Conc of substance in urine / concentration of substance in blood ) x urine flow rate = GFR [urine flow rate = urine volume / time in minutes ]

83
Q

What criteria are needed to choose a substance to measure to calculate GFR?

A

Substances that are only filtered, not toxic and not metabolized by the body = creatinine and inulin

84
Q

What is inulin?

A

Polysaccharide

85
Q

Difference between measuring GFR with inulin and creatinine?

A

Creatinine does NOT need to be administered = endogenous susbstance UNLIKE inulin

86
Q

What happens if you cannot use collect creatinine in the urine to measure creatinine clearance?

A

Use plasma creatinine concentrations

87
Q

What is the relationship between plasma creatinine conc and GFR?

A

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Human Physiology Y3 (14 decks)

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