Physiology - RENAL Flashcards
What is normal range of plasma oncotic pressure?
25 - 28 mmHg
Identify the normal body volumes of (as a percentage): Water Proteins and related substances Minerals Fat
Water: 60%
Proteins and related substances: 18%
Minerals: 7%
Fat: 15%
What factors affect total body water?
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)
Identify the tonicity of the following:
- Isosmotic = ?
- Hypoosmotic = ?
- Hyperosmotic = ?
- Isosmotic = Isotonic
- Hypoosmotic = Hypotonic
- Hyperosmotic = Hypertonic
Which structure has the MOST water content percentage?
Bone, Fat or Organs
Organs = 70 - 80% Bone = 35 % Fat = 10 - 20 %
How is body water calculated in L?
L = 60/100 (% of body water as a fraction) x 70 (Kg of individual)
What does extracellular and intracellular fluid consist of?
Extracellular: Plasma + interstitial fluid
Intracellular: Fluid surrounding the cells which is separated from plasma
Formula for volume distribution?
V = Q/C V = Volume distribution Q = Amount of dye known added to body compartment C = Concentration measurement after mixing (body compartment + dye)
What type of cells separate the plasma and interstitial fluid?
Endothelial cells
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 = ?
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)
What indicators can be use to measure total body water?
Hint: 2
- Antipyrine
- Tritiated water/heavy water
What indicators can be use to measure extracellular fluid?
Hint: 4
- Na (Sodium)
- Inulin
- Thiosulfate
- I-iothalamate
What indicators can be use to measure intracellular fluid ?
- Intracellular fluid = Total body water - extracellular fluid
What indicators can be use to measure plasma volume?
Hint: 2
- Radioactive albumin
- Evans blue dye (strongly binds to albumin which stays in the plasma compartment)
What indicators can be use to measure blood volume?
Hint: 3
- Radiolabelled chromium-51
- Techetium-99m
- blood volume = plasma volume/ haematocrit
What indicators can be use to measure interstitial fluid?
- (Calculated as Extracellular fluid volume - plasma volume)
How is interstitial fluid measured?
- Interstitial fluid = Extracellular fluid - plasma volume
Compare the charge and osmolality of the intracellular compartment and extracellular compartment.
- 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
- Intracellular
- Cations: Potassium, magnesium, calcium, sodium
- Anions: Organic phosphates e.g. ADP, proteins, proteins, bicarbonate
Describe the extracellular fluid
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
Describe the intracellular fluid
Intracellular
- Different cells = different functions, therefore different charges
- The main ion are organic phosphate e.g. ATP
How is plasma and interstitial fluid composition maintained/controlled?
- Capillaries - tend to hold more proteins, proteins don’t readily move across the membrane
- The Gibbs-Donnan Effect….Proteins attracting cations (+) and repelling anions (-). Therefore plasma has a sodium and lower chloride than interstitial fluid.
How is extracellular and intracellular fluid composition maintained/controlled?
- Cell membrane is MORE selectively permeable than capillary endothelium
- Selective ion pumps e.g. Na+/K+ -ATPase
- The Gibbs-Donnan effect because of the proteins contained within cells
How is total body water maintained/controlled?
- Thirst, kidney, Antidiuretic Hormone (ADH)
What is the function of the kidneys
- 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