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HMB > Physiology - RENAL > Flashcards

Physiology - RENAL Flashcards

1
Q

What is normal range of plasma oncotic pressure?

A

25 - 28 mmHg

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2
Q 
Identify the normal body volumes of (as a percentage): 
Water 
Proteins and related substances 
Minerals 
Fat
A

Water: 60%
Proteins and related substances: 18%
Minerals: 7%
Fat: 15%

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3
Q

What factors affect total body water?

A

Age: Newborns (75%) have more water than older people (50%)
Obesity: Obese people have less boy water % (Due to higher fat content)
Gender: Females have less body water % than males (Due to higher fat content)

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4
Q

Identify the tonicity of the following:

  1. Isosmotic = ?
  2. Hypoosmotic = ?
  3. Hyperosmotic = ?
A
  1. Isosmotic = Isotonic
  2. Hypoosmotic = Hypotonic
  3. Hyperosmotic = Hypertonic
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5
Q

Which structure has the MOST water content percentage?

Bone, Fat or Organs

A 
Organs = 70 - 80% 
Bone = 35 % 
Fat = 10 - 20 %
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6
Q

How is body water calculated in L?

A

L = 60/100 (% of body water as a fraction) x 70 (Kg of individual)

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7
Q

What does extracellular and intracellular fluid consist of?

A

Extracellular: Plasma + interstitial fluid
Intracellular: Fluid surrounding the cells which is separated from plasma

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8
Q

Formula for volume distribution?

A 
V = Q/C 
V = Volume distribution 
Q = Amount of dye known added to body compartment 
C =  Concentration measurement after mixing (body compartment + dye)
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9
Q

What type of cells separate the plasma and interstitial fluid?

A

Endothelial cells

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10
Q

Identify the % of body weight of the following and the volume fraction of the following:

Total body water (TBW) = ?
Extracellular volume (ECV) = ?
Intracellular volume (ICV) = ?
Plasma = ?
Interstitial fluid = ?
A 
Total body water (TBW) = 60% of body weight 
Extracellular volume (ECV) = 20% of body weight (1/3 of TBW)
Intracellular volume (ICV) = 40% of body weight. (2/3 of TBW)
Plasma = 5% of body weight. (1/4 of ECV)
Interstitial fluid = 15% of body weight. (3/4 of ECV)
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11
Q

What indicators can be use to measure total body water?

Hint: 2

A
  • Antipyrine

- Tritiated water/heavy water

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12
Q

What indicators can be use to measure extracellular fluid?

Hint: 4

A
  • Na (Sodium)
  • Inulin
  • Thiosulfate
  • I-iothalamate
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13
Q

What indicators can be use to measure intracellular fluid ?

A
  • Intracellular fluid = Total body water - extracellular fluid
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14
Q

What indicators can be use to measure plasma volume?

Hint: 2

A
  • Radioactive albumin

- Evans blue dye (strongly binds to albumin which stays in the plasma compartment)

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15
Q

What indicators can be use to measure blood volume?

Hint: 3

A
  • Radiolabelled chromium-51
  • Techetium-99m
  • blood volume = plasma volume/ haematocrit
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16
Q

What indicators can be use to measure interstitial fluid?

A
  • (Calculated as Extracellular fluid volume - plasma volume)
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17
Q

How is interstitial fluid measured?

A
  • Interstitial fluid = Extracellular fluid - plasma volume
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18
Q

Compare the charge and osmolality of the intracellular compartment and extracellular compartment.

A
  • The intracellular compartment has MORE total charges than the extracellular compartment. This is due to higher protein content in the intracellular compartment and that proteins are polyvalent.
  • Osmolality in each compartment is the same
    1. Extracellular
    Plasma:
  • Cations: Sodium, calcium, potassium, magnesium
  • Anions: Chlorine, bicarbonate, protein
    Interstitial:
  • Cations: sodium, potassium, calcium
  • Anions: Chlorine, bicarbonate, sulphate
  1. Intracellular
    - Cations: Potassium, magnesium, calcium, sodium
    - Anions: Organic phosphates e.g. ADP, proteins, proteins, bicarbonate
19
Q

Describe the extracellular fluid

A

Extracellular

  • Both plasma and interstitial fluid is similar, containing similar amounts of sodium, chloride and bicarbonate
  • There is more protein in the plasma compartment than interstitial
  • There is more sodium and less chloride in plasma due to the negatively charged protein
20
Q

Describe the intracellular fluid

A

Intracellular

  • Different cells = different functions, therefore different charges
  • The main ion are organic phosphate e.g. ATP
21
Q

How is plasma and interstitial fluid composition maintained/controlled?

A
  1. Capillaries - tend to hold more proteins, proteins don’t readily move across the membrane
  2. The Gibbs-Donnan Effect….Proteins attracting cations (+) and repelling anions (-). Therefore plasma has a sodium and lower chloride than interstitial fluid.
22
Q

How is extracellular and intracellular fluid composition maintained/controlled?

A
  1. Cell membrane is MORE selectively permeable than capillary endothelium
  2. Selective ion pumps e.g. Na+/K+ -ATPase
  3. The Gibbs-Donnan effect because of the proteins contained within cells
23
Q

How is total body water maintained/controlled?

A
  • Thirst, kidney, Antidiuretic Hormone (ADH)
24
Q

What is the function of the kidneys

A
  • Vitamin D production (active form 125-ihydryoxy) is made in kidneys
  • Gluconeogenesis
  • Regulation of RBC - erythropoietin
  • Maintain arterial blood pressure - sodium balance, renin (causes vasoconstriction), vasoactive substances, prostaglandins (causes vasodilation)
  • Detox
  • Acid-base regulation (production of bicarbonate if needed)
  • Water and electrolyte balance
25
Q

Describe the 4 types of filtration in the kidneys?

A
  1. Free filtration
    - The substance is full secreted with urine
    - E.g. inulin
  2. Partial reabsorption
    - Some of the substance is secreted, however some of it is reabsorbed back into the blood
    - E.g. Vitamin C
  3. Complete reabsorption
    - The substance is 100% reabsorbed and is NOT secreted
    - E.g. Glucose (in healthy people)
  4. Secretion
    - The substance is fully excreted with urine out the body
    - E.g. Para-amino
26
Q

What is normal renal blood flow in males and females?

A 
Males = 1.2L/min 
Females = 900mL/min
27
Q

How is renal plasma flow (RPF) calculated?

A

Renal plasma flow = Renal Blood flow (RBF) x (100 - Hct%)/100

Hct% = % of hematocrit blood

28
Q

What is autoregulation? and the normal autoregulatory range

A
  • Autoregulation is a compensatory mechanisms which helps to minimise the changes within the glomerular filtration rate (GFR) and real blood flow (RBF) at different blood pressure values
  • It is an intrinsic response (no hormonal or neural control)
  • There are 2 types of autoregulation:
    1. Myogenic
    2. Tubularglomeulerar feedback macular densa
  • Range = 80mmHg - 170mmHg
29
Q

Compare blood flow and oxygen levels in the kidneys

A

Kidneys have a high blood flow rate- accounting for 20-25% of blood flow from resting cardiac outflow, and is considerably higher than blood flow to other organs e.g. brain. This is necessary for the blood to be filtered and is by no means equilevant to the oxygen levels supplied to the kidneys (which is smaller)

30
Q

Renin is produced why which cells?

A

Granular cells (juxtaglomerular cells) located in the afferent arteriole

31
Q

Describe the Rennin-angiotensin system

A
  1. Rennin is produced by granular cells in the afferent arteriole
  2. Rennin cleaves angiotensinogen (produced in the liver) to produce angiotensin 1
  3. Angiotensin I is then cleaved by angiotensin converting enzyme to angiotensin II. (Note angiotensin converting enzyme also metabolises bradykinin - stopping vasodilation).
  4. Angiotensin II acts up AT1 and AT2 receptors (however action occurs mainly on AT1 receptors)
32
Q

What is a juxtaglomerular apparatus and what does it consist of?

A
  • Function: Regulate blood pressure and the filtration rate of the glomerulus.
  • Located: Vascular pole of the glomerulus
  • It is formed by the distal convoluted tubule and the glomerular afferent arteriole.

Four components
- Juxtaglomerular cells: smooth muscle cells located in the walls of the afferent arterioles which produce rennin and are innervated by sympathetic nervous system

  • Macular dense cells: Are located between the thick acceding loop of Henle and distal convoluted tube. They sensitive to ionic content and water volume.
  • Mesangial cells and mesangial matrix: Located between the glomerular capillaries. Produces substances which contribute to the matrix and immune complex clearance via phagocytosis.
  • Glomerular capillaries
33
Q

How is Rennin release controlled?

A
  1. Renal baroreceptor - drop in BP in afferent arteriole –> release of renin
  2. Macular densa - reduction in NaCl delivery –> release of renin
  3. Renal sympathetic nerves - increase renin release via B1 receptor
  4. Feedback control
    a. Increase in intravasular volume, blood pressure and improved renal perfusion inhibit release (long feedback loop)
    b. Short feedback loop - AngII acts on JG cells to inhibit release
  5. Other
    a. Increase - chronic hypokalaemia, PGE2
    b. Decrease - acute hypernatremia, ADH, ANF
34
Q

What affects does angiotensin II have on the vascular system?

A
  • Arteriolar vasoconstriction (most potent known vasoconstriction)
35
Q

What affects does angiotensin II have on the renal system?

A
  • Vasoconstriction
  • Proximal sodium reabsorption
  • Contraction of mesangial cells - decrease the area for filtration
36
Q

What affects does angiotensin II have on the adrenal system?

A
  • Aldosterone release
37
Q

What affects does angiotensin II have on the neural system?

A
  • Facilitates sympathetic activity
  • Inhabits vagus = decrease of baroreflex
  • Increases ADH secretion
  • Increases ACTH secretion
  • Dipsogen - stimulates thirst
38
Q

Renal sympathetic nerve effects:

A
  1. Vasoconstriction via a1-adrenoreceptors

2. Renin release by B-adrenoreceptors on JG cells

39
Q

What type of renal neurons supply the major afferent and efferent arterioles of the kidney, JG cells and proximal tubules?

A

Sympathetic noradrenergic neurons

40
Q

What is normal Glomerular Filtration Rate (GFR)?

A

Males: 125ml/min - 180L/day

41
Q

Describe the histology of the glomerular structure

A
  • Increased capillary loops = increase in SA filtration
  • Mesangial cells and mesangial matrix - located between capillary loops. The cells are phagocytic and contractile (alter SA for glomerular filtration) + substance secretion
  • Podocytes - located on the glomerular capillary and extend over the capillaries to form numerous filtration slits (that are covered by slit diaphragms). It functions to filtrate - only letting small molecules pass. Podocytes can reduce GFR by contracting close to slits = reduction in SA or filtration
42
Q

Identify the various filtration barrier features that regulate the movement across the basement membrane of the kidneys

A
  • Fenestrations
  • Glycoialoprotein coat: negatively charged to prevent movements of ions e.g. in minimal change nephropathy
  • Slit diaphragm: Restrict substance size
  • Podocytes and foot processes: Form filtration slits
  • Basement membrane: three layers (main barrier)
43
Q

Identify the factors that can affect GFR

A
  • Renal blood flow

- Changes in pressure glomerular capillaries (Pgc)

HMB (34 decks)

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