An introduction to kidneys and body fluid Flashcards
(54 cards)
what does osmosis determine?
the movement of water between ICFV and ECFV
why might we want to prevent large fluid shifts between ICFV and ECFV?
too much water into cells will make them burst, causing tissue damage
too much water out causes them to shrink massively
ECFV
The ECFV consists of two sub-compartments:
Plasma (3L) - usually 20% of ECV
Interstitial fluid (11L)
Starling forces determine fluid and solute movement between plasma and interstitial fluid
how much of the body weight is ICV?
40%
what is osmolarity?
the total concentration of osmotically active solutes
what is the major determinant of ECV osmolarity and why?
sodium, because it is the principal electrolyte of ECF
Why is the control of body fluids important ?
Cell structure and function
-large shifts between ECFV and ICFV will disrupt tissue structure and function
Tissue perfusion
-depends on balance between circulating volume (plasma) and interstitial volume
what determine fluid and solute movement between plasma and interstitial fluid?
Starling forces
what do salt and water balance depend on?
Osmoregulation: maintain osmotic equilibrium between ICFV and ECFV
Volume regulation: maintain adequate ECFV to support plasma volume
why do we control ECFV osmolarity?
in order to maintain osmotic equilibrium between ICFV and ECFV
how can plasma osmolarity be estimated?
2[Na] + 2[K] + [glucose] + [urea]
(Why do we double sodium and potassium but not glucose and urea? Balance the charges, if you have a certain amount of sodium there is positive charge which needs to be balanced out with anions (most of the anions will be made up of chloride, but it also includes bicarbonate and other molecules). Glucose is not charged so isn’t doubled
give a difference between interstitial fluid and plasma fluid?
plasma proteins (cannot cross the plasma membrane)
how does the body achieve osmoregulation?
by adding or removing water (not sodium) through controlling by controlling ADH levels
when plasma osmolarity rises how do the kidneys respond?
by producing small volume of concentrated urine (water retention)
a rise in plasma osmolarity indicates what?
that solute concentration has gone up (so more water is needed)
what does volume regulation refer to?
the control of the circulating (plasma) volume
what are changes in plasma volume detected by?
stretch and pressure receptors in the CVS
what is a fall in blood volume opposed by?
sodium retention - water follows osmotically, restoring volume
(although the total amount of body sodium may be increased, osmolarity is barely changed because the retained sodium brings water with it)
function of the kidney?
salt and water balance
- Osmoregulation
- Volume regulation
- Acid-base balance
- Regulation of electrolytes balance (eg potassium, calcium, phosphate)
- Removal of metabolic waste products from blood
- Removal of foreign chemicals in the blood (e.g. drugs)
- Regulation of red blood cell production (erythropoietin)
- endocrine organ (EPO, renin, Vit D)
what is urine production?
a by-product of kidney function
urinary tract
important for temporary storage, then removes urine from the body
what is a nephron?
functional unit of the kidney -consists of special blood vessels and elaborate tubules (tiny tubes) -where urine production begins -consists of several major structures: Blood vessels The glomerulus Bowman capsule The renal tubule
what are the outer and inner sections of the kidney called?
outer - cortex
inner - medulla
explain how the kidney (and nephrons) are supplied with blood
The whole kidney is supplied by a major artery called the renal artery
This subdivides many times into fine arterioles supplying each nephron, the afferent arteriole
Drained by the renal vein, which is supplied by venules coming away from each nephron, joining together into larger veins which merge into the renal vein.
In between there are complex capillary networks
