HUBS192 Lecture 33 - Renal Physiology: Body Water - Distribution and Regulation Flashcards
what drives and regulates body water homeostasis?
- distribution of body water
- osmolarity/tonicity of solutions
- reabsorption of water in the nephron
- changes in body osmolarity
- effects of osmotic changes in the kidney
how many percent of our total body weight (TBW) is water?
55-60%
how much of our total body weight (TBW) water is stored in the intracellular fluid (ICF)?
2/3
how much of our total body weight (TBW) water is stored in the extracellular fluid (ECF)?
1/3
how much of the water stored in the extracellular fluid (ECF) is stored as plasma?
1/5
how much of the water stored in the extracellular fluid (ECF) is stored as interstitial fluid?
4/5
what is osmolarity based on?
based on the number of osmotically active ions or solutes
what molecules determine osmolarity?
- Na+
- CI-
- H2O
how can osmolarity be estimated?
can be estimated by specific gravity (density of solutions)
what is iso-osmotic?
same osmolarity solutions
what is hypo-osmotic?
low osmolarity solutions
what is hyper-osmotic?
high osmolarity solutions
what is tonicity based on?
based on the effect of a solution on cells
what is an isotonic solution?
a solution that does not change water homeostasis between cells
what is the relationship between the composition of ECF, ICF and osmolarity?
no matter what the composition of ECF and ICF, osmolarity will always be in balance (have the same values for both ECF and ICF)
does total body water remain constant?
yes, total body water remains relatively constant
what are the 4 important places within the nephron where Na+ is reabsorbed?
1) proximal convoluted tubule (PCT)
2) the nephron loop
3) distal convoluted tubule (DCT)
4) collecting duct (CD)
where is 67% of the filtered load of Na+ reabsorbed in the nephron?
in the proximal convoluted tubule (PCT)
where is 25% of the filtered load of Na+ reabsorbed in the nephron?
in the nephron loop
where is 5% of the filtered load of Na+ reabsorbed in the nephron?
in the distal convoluted tubule
where is 3% of the filtered load of Na+ reabsorbed in the nephron?
in the collecting duct
how much percent of the filtered load of Na+ reabsorbed in the nephron is reabsorbed in the proximal convoluted tubule?
67%
how much percent of the filtered load of Na+ reabsorbed in the nephron is reabsorbed in the nephron loop?
25%
how much percent of the filtered load of Na+ reabsorbed in the nephron is reabsorbed in the distal convoluted tubule?
5%
