An Intro To Kidney And Body Fluids Flashcards
What do osmolarity and osmolality refer to?
The total concentration of osmotically active particles in solution
What is the difference between osmolarity and osmolality?
Osmolarity is the measure of solute concentration per unit volume of solution and osmolality is per unit mass of the solvent
What % of water are males?
60%
What % of water are females?
50%
What are the two main fluid compartments?
Intracellular and extracellular fluids
What proportions are the body’s fluids stored in?
2/3 intracellular and 1/3 extracellular
What must the Intracellular fluid and Extracellular fluid be in?
Osmotic equilibrium
What happens if the solute concentration changes in either the intracellular or extracellular fluid compartments?
Generate an osmotic gradient, resulting in shifts of water between compartments
What is regulated in the extracellular fluid compartment?
Osmolarity
Why is osmolarity regulated in the ECF?
To avoid osmotic shifts of water between the ICF and ECF volumes
What is the normal range of osmolarity?
280-300 mosm/L
Why must large shifts in osmolarity be avoided?
Prevent changes in cell volume
What are the main serious complications of a large shift in osmolarity?
Demyelination, decrease in cell volume -> blood vessels bursting
What is osmoregulation?
Physiological process that maintains constant ECF osmolarity
What is the ECF compartment subdivided into (and in what proportions)?
Interstitial (extravascular) compartment (75%)
Plasma (vascular) compartment (25%)
What does maintaining salt and water balance require?
Integration of osmoregulation and volume regulation
How does osmoregulation control salt concentration?
Adjusts the amount of pure water in the body
What does volume regulation do?
Controls the amount of salt and water in the ECF and therefore ECF volume
Which organ is central to both osmoregulation and volume regulation?
Kidney
What is the function of the kidneys?
Homeostasis
What are the other functions (not homeostasis) of the kidneys?
- osmoregulation
- volume regulation
- Acid-base balance
- regulation of electrolyte balance
- removal of metabolic waste products and foreign chemicals in the blood
- regulation of RBC production
What are the four basic processes of renal function?
Glomerular filtration, tubular reabsorption, tubular secretion and excretion of water and solutes in the urine
What drives water and solutes across the capillary membrane in glomerular filtration?
Balance of starling forces
What causes plasma ultrafiltration in the bowmans capsule?
The inability of large proteins and cells to pass through the capillary membrane so creating an osmotic force
What is the glomerular filtration rate?
The amount of filtrate produced by kidneys each minute
What is the average glomerular function rate?
125mL/min
What can glomerular filtration rate be used for?
As an indicator for renal function?
How much of the salt and water is reabsorbed from the proximal tubule?
70%
What is tubular secretion important in?
Eliminating toxins and metabolic byproducts and potassium and acid balance
Where is excess potassium secreted?
Distal tubule and collecting duct
What does the acid base balance rely on?
Hydrogen ion secretion in the distal tubule and collecting duct
What is urine?
Tubular fluid that remains after reabsorption and secretion
What is the amount of water and solutes equal to?
Amount filtered - amount reabsorbed + amount secreted
What can be used to measure glomerular filtration rate?
Creatinine
What happens if you add water to the ECF?
ECF diluted-> water moves down the osmotic gradient into ICF -> ECF and ICF both expand and there is increased renal water filtration
What happens to the osmolarity if you loose water?
Increases
What happens physiologically if your plasma osmolality rises?
Increased thirst and increased secretion of ADH
What is a synonym for ADH?
Vasopressin
What does ADH do?
Increase renal water reabsorption
So decreases urine volume and increases urine osmolality
What happens to the plasma osmolality if there’s an increase in water intake?
Falls as there’s increased water absorption through the GIT
What are the physiological responses to a decrease in plasma osmolality?
Decreased thirst and secretion of ADH
What does decreased plasma osmolality result in for urine?
Increased volume and decreased osmolality
How is ECF volume determined?
The amount of sodium in that compartment
What must be balanced to maintain a constant ECF volume?
Sodium intake and excretion
Where are the main volume sensors?
CV system
What happens to the ECF and ICF volumes if you add an isotonic solution to the ECF?
Retained in the ECF as the overall salt concentration hasn’t changed, so no change in osmotic gradient
What does the renin-angiotensin-aldosterone system do?
Increases renal sodium reabsorption and increases ECF volume
What do cardiac natriuretic peptides do?
Decrease renal sodium reabsorption and decrease ECF volume
