Introduction to kidneys + body fluid Flashcards
What percentage of the body is water ?
60% water in males, 50% in females
Ratio of water composition in ECF and ICF
2/3 intracellular
1/3 extracellular
How permeable is the cell membrane?
SEMI permeable
- Permeable to water (via water channels: aquaporins)
- Impermeable to most solutes
What is the main electrolyte in ECF?
Na
What is the main electrolyte in ICF?
K
What is osmoregulation?
physiological process that maintains constant ECF osmolarity
avoids osmotic shifts of water between ECF and ICF compartments, and potential cell/tissue damage
What are the subdivisions of ECF?
- Interstitial (or extravascular) compartment (about 75% of ECF)
- Plasma (or vascular) compartment (about 25% of ECF)
What is the difference between volume regulation and osmoregulation?
Osmoregulation controls salt CONCENTRATION
Volume regulation controls AMOUNT of salt
List some functions of the kidneys
- Osmoregulation
- Volume regulation
- Acid base balance
- Regulation of electrolyte balance
-Removal of metabolic waste products from blood - Removal of foreign chemicals
- Regulation of red blood cell production (erythropoietin)
How many nephrons per kidney?
1.25 MILLION
What is the average GFR?
125ml/min
approx 20 % of renal plasma flow!!!!!!!
What percentage of filtered salt and water are reabsorbed in the PCt and the loop of henle?
70% from PCT
20-25% from loop of henle
Where is excess potassium secreted?
Distal tubule and collecting duct
What ion is secreted to maintain acid-base balance? (and where)
H+
Secreted in distal tubule and collecting duct
Explain the process that occurs when there is a change in water intake/excretion
- Change in body fluid osmolality
- Sensor (osmoreceptors in hypothalamus)
3.Effector( ADH) - Change in renal excretion
Where does ADH act on ?
Collecting duct
What does osmolality 50 (mOsm/kg) mean?
maximum dilution of urine by kidney, therefore maximum water excretion
what does osmolality 1200 mean?
Maximum concentration of urine
minimum amount of water lost
What two systems can increase/decrease sodium retention?
RAAS - Increases renal Na reabsorption - Increases ECF volume
Cardiac natriuretic peptides (ANP) - Decreases renal Na reabsorption-Decreases ECF volume
Does RAAS sense Na+ conc?
RAAS does not sense Na concentration.
Na is inferred from the ECF volume, which is sensed via the CV system.
