An intro to kidney and body fluids Flashcards
Total body water
60% body weight
Intracellular water
40% body weight (ICF compartment)
Extracellular water
20% body weight (ECF compartment)
What does osmosis determine?
The movement of water between ICF and ECF
What is the plasma compartment sometimes called?
Effective circulating volume. Normally 20%
What does the ECFV consist of?
Plasma (3L) Interstitial fluid (11L) Starling's forces determine fluid and solute movement between plasma and interstitial fluid
What is OSMOLARITY?
The total concentration of osmotically active solutes.
What electrolyte is the principle for ECF?
Sodium - important for ECF osmolarity
Why is control of body fluids important?
Cell structure and function - Large shifts between ECFV and ICFV will disrupt tissue structure and function.
Tissue perfusion - Depends and balance between circulating volume (plasma) and interstitial volume
Salt and water balance depends on what 2 processes?
Osmoregulation: maintain osmotic equilibrium between ICFV and ECFV
Volume regulation: maintain adequate ECFV to support plasma volume
Plasma osmolarity can be estimated by
2[Na] + 2[K] + [glucose] + [Urea] all in mmol-1
How does the body accomplish osmoregulation?
By adding or removing water not sodium
What happens when your plasma osmolarity rises?
More water is needed. So the kidney responds by producing a small volume of concentrated urine (water retention)
What happens when your plasma osmolarity falls?
There is too much water. So the kidneys respond by producing large volumes of dilute urine (water excretion)
What is volume regulation?
Refers specifically to the control of the circulating (plasma) volume
How are changes in plasma detected?
Stretch and pressure receptors in the cardiovascular system.
What are the first 3 functions of the kidney?
Osmoregulation
Volume regulation
Acid-base balance
What are the other 4 functions of the kidney?
Regulation of electrolytes balance (e.g K+, Ca 2+, PO4 3-)
Removal of metabolic waste products from blood
Removal of foreign chemicals in the blood
Regulation of red blood cell production
How many nephrons are in one kidney?
1.25 million per kidney
Where urine production begins
What are the major structures of the nephron?
Blood vessels
The glomerulus
Bowman capsule
The renal tubule
What are the 4 basic processes of urine formation?
Glomerular filtration
Tubular reabsorption
Tubular secretion
Excretion of water and solutes
What is GFR?
Glomerular filtration rate
Also averages 125/ml/min
Is reduced in renal failure
Plasma creatine can be used as an index of GFR
What happens when there is a loss of water but there is no water available?
Plasma osmolality rises
Increase in ADH/ vasopressin
Leads to decreased urine volume and urine osmolality
Increase in water absorption through GIT
Plasma osmolality falls, less secretion of ADH/ vasopressin
Urine volume increases
Urine osmolality decreases
What are the 2 systems in place for controlling Sodium
RAAS
ANP
RAAS
Renin-angiotensin-aldosterone system
ANP
Cardiac Natriuretic Peptides
