Introduction to kidneys and body fluid Flashcards
What is the total body water as a %?
→ 60%
How much is intracellular water?
→ 40%
How much is extracellular water?
→ 20%
What is osmoregulation?
→ process where the concentration of solutes is regulated
Why is osmoregulation needed?
→ to avoid large disruptive movements of water between ICF and ECF
What is the plasma compartment sometimes called?
→ Effective circulating volume
What do starling forces determine?
→ Fluid and solute movement between plasma and interstitial fluid
What is osmolarity?
→ total concentration of osmotically active solutes
Why must osmolarity be kept the same?
→ Avoid excessive shifts of water between ECF and ICF
What is the principal electrolyte of the ECF?
→ Sodium
Why can ECF be regulated?
→ It is continuous
How many compartments is the ICF made from?
→ 1x10^14
What are the concentrations of Na+ in mmol/L in ICF and ECF?
ECF : 135-145
ICF - 5-10
What are the concentrations of K+ in mmol/L in ICF and ECF?
ECF : 3-5
ICF : 130-150
What will large shifts between ECFV and ICFV cause?
→ disrupts tissue function and structure
What does tissue perfusion depend on?
→ Balance between circulating volume and interstitial volume
What do salt and water balance depend on?
→ Osmoregulation
→ Volume regulation
What does osmoregulation maintain?
→ Maintains osmotic equilibrium between ICFV and ECFV
What does volume regulation maintain?
→adequate ECFV to support plasma volume
What is the equation for investigating plasma osmolarity?
→2[Na] + 2[K] + [Glucose] + [Urea] (all in mmol L-1)
What is the ion that has the biggest impact on osmolarity?
→ Na+
Why can other ions be neglected as contributing to osmolarity?
→they are present in much lower concentrations
What are the two ways to change the osmolarity of a solution?
→Add/Remove Solute
→Add/Remove Water
How do the kidneys respond when plasma osmolarity rises?
→ More water needed
→Kidneys respond by producing a small volume of concentrated urine (water retention)
How do the kidneys respond when plasma osmolarity falls?
→ Too much water
→Kidneys respond by producing a large volume of dilute urine (water excretion)
What volume does volume regulation refer to?
→Circulating plasma volume
What are volume changes detected by?
→Stretch and pressure receptors in the CVS
What is a fall in blood volume opposed by?
→ Sodium retention
→ water follows osmotically
→restoring the volume
Why does an increase in sodium not cause a huge change in osmolarity?
→the concentration (and hence osmolarity) is little changed because the retained sodium brings water with it.
What is the kidneys central function?
→ Salt and water balance