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Human Physiology - Hormones and Health > Kidney and Glomerular Filtration > Flashcards

Kidney and Glomerular Filtration Flashcards

1
Q

What are the functions of the kidney?

A
  • excretion of metabolic waste products and foreign chemicals
  • regulation of water and electrolyte balances
  • regulation of RBC production
  • synthesis of vitamin D3
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2
Q

What are the 2 most important parts of the kidney?

A

cortex and medulla

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3
Q

What is the functional unit of the kidney?

A

the nephron

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4
Q

What does each nephron consist of?

A
  1. glomerulus
  2. tubule
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5
Q

What is the glomerulus formed by?

A

the invagination of a tuft of capillaries into the dilated blind end of the nephron (Bowman’s capsule)

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6
Q

What is Bowman’s capsule?

A

the cup-like structure formed when blood vessels form and invaginate in the tubule at the bottom of the basement membrane

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7
Q

What does the afferent arteriole do?

A

enter into the glomerulus and bring in blood before breaking off into capillaries that gather to form an efferent arteriole

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8
Q

What are the 2 cellular levels that separate the blood from the glomerular filtrate?

A
  1. capillary endothelium
  2. specialised epithelium of the capsule
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9
Q

What is the capillary endothelium surrounded by?

A

the glomerular basement membrane (GBM) and specialised cells called podocytes

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10
Q

What do podocytes do?

A

interdigitate to form filtration slits along the capillary walls

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11
Q

Where are mesangial cells located?

A

between the GBM and endothelium

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12
Q

What does the glomerulus open into?

A

the proximal convoluted tubule

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13
Q

What are the 7 components of the renal tubule?

A
  • Bowman’s capsule
  • proximal tubule
  • descending limb of loop of Henle
  • thin ascending limb of loop of Henle
  • thick ascending limb of loop of Henle
  • distal tubule
  • collecting tubule
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14
Q

What is the juxtaglomerular complex?

A

where the efferent and afferent arterioles come together with the distal tubule

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15
Q

What does the juxtaglomerular complex consist of?

A
  • macula densa cells in the initial portion of the distal tubule
  • juxtaglomerular cells in the walls of the arterioles
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16
Q

What is the macula densa?

A

a specialised group of epithelial cells in the distal tubules that come in close contact with the afferent and efferent arterioles

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17
Q

What are functions of the juxtaglomerular complex?

A
  • regulation of BP
  • glomerular filtration
  • sodium reabsorption
  • synthesis of renin
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18
Q

What type of nephron is more rare and what do they do?

A

juxtamedullary nephrons that concentrate and dilute urine

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19
Q

What percentage of CO is renal blood flow?

A

~22% (1100 ml/min)

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20
Q

What are the 2 capillary beds of the renal circulation?

A
  • glomerular capillaries
  • peritubular capillaries
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21
Q

What is the GFR?

value

A

180L/day

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22
Q

What are the 4 degrees of filtration and absorption of the renal system?

A
  • filtration only e.g. inulin
  • filtration and partial reabsorption e.g. electrolytes
  • filtration and complete reabsorption e.g. amino acids, glucose
  • filtration and secretion e.g. certain drugs, creatinine
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23
Q

What appears in high and low volumes in the urine respectively?

A
  • high = end products of metabolism e.g. urea, creatinine
  • low = electrolytes e.g. sodium, chloride, bicarbonate ions
24
Q

What is completely reabsorbed into the blood?

A

glucose and amino acids

25
Q

How does the body respond to excess sodium?

A
  • increased rate of sodium filtration
  • reduced rate of sodium reabsorption
26
Q

What is GFR?

A

the amount of plasma ultrafiltrate formed each minute

27
Q

What is FF?

A

the fraction of renal plasma flow filtered across the glomerulus

28
Q

What is the formula for FF?

A

FF = GFR/renal plasma flow

29
Q

What are the 3 determinants of GFR?

A
  • size of the capillary bed (surface area)
  • permeability of the capillaries
  • hydrostatic and osmotic pressure gradients across the capillary wall
30
Q

What does the glomerular ultrafiltration coefficient (Kf) describe?

A

the ease (or difficulty) with which water migrates across the filtration membrane

31
Q

What is the formula for Kf?

A

Kf = glomerular capillary permeability x filtration surface area

32
Q

What does contraction of mesangial cells cause?

A

a reduction in the area available for filtration

33
Q

What regulates mesangial contraction?

A

angiotensin II

34
Q

What is the glomerular capillary permeable to?

A
  • molecules less than 4nm
  • positively charged non-proteins
35
Q

What is albumin?

A

a negatively charged plasma protein repelled by the glomerular capillary despite its small size

36
Q

What is glomerulonephritis?

A

a condition where immune cells attack and damage the glomerulus; the negative charge is lost and albumin can enter the urine

37
Q

Which forces favour filtration?

A
  • glomerular capillary BP
  • net filtration pressure
38
Q

Which forces oppose filtration?

A
  • plasma-colloid osmotic pressure
  • Bowman’s capsule hydrostatic pressure
39
Q

What must happen for substrates to filter into Bowman’s capsule?

A

the pressure in the capillaries must be higher than in the glomerulus

40
Q

What is hydrostatic and colloid osmotic pressure generated by respectively?

A
  • hydrostatic = pressure of fluids
  • colloid osmotic = proteins attracting water
41
Q

What reduces filtration surface area?

A
  • ageing
  • diabetes
  • renal diseases
42
Q

What do kidney stones cause?

A

the Bowman capsule pressure to increase and oppose the filtration forces

43
Q

What are the effects of increased sympathetic activity on GFR?

A
  1. ↑ sympathetic activity e.g vasoconstrictor hormones
  2. afferent arteriolar constriction
  3. ↓ renal blood flow
  4. ↓ hydrostatic pressure
  5. ↓ GFR
44
Q

What are the effects of increased angiotensin II on GFR?

A

efferent arteriole constriction which increases GFR

45
Q

How is GFR maintained at low BP?

A

angiotensin II constricts the efferent arterioles

46
Q

What is tubuloglomerular feedback?

A

a special feedback mechanism that links changes in the sodium chloride concentration at macula densa with the control of renal arteriolar resistance and autoregulation of GFR

47
Q

How is blood flow increased to the kidney?

A

the afferent arteriole dilates to decrease resistance

48
Q

What is plasma clearance?

A

the volume of plasma necessary to supply the amount of substance excreted in the urine per unit of time

49
Q

What is the formula for clearance rate?

A

clearance rate = (concentration in urine x urine flow)/concentration in plasma

50
Q

What is the formula for urine flow?

A

urine flow = urine volume/time

51
Q

When is the rate of excretion in urine equal to GFR?

A

when a substance is freely filtered and is not reabsorbed or secreted by the renal tubules

52
Q

How is GFR measured?

A

using the excretion of substances that are non-toxic or metabolised by the body e.g. inulin or creatinine

53
Q

How can an approximation of changes in GFR be obtained?

A

by measuring the plasma creatinine concentration (PCr)

54
Q

What is the relationship between PCr and GFR?

A

inversely proportional

55
Q

When is a substance secreted into renal tubules?

A

when its clearance is greater than GFR

56
Q

When is a substance reabsorbed in the renal tubules?

A

when its clearance is less than GFR

Human Physiology - Hormones and Health (14 decks)

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