Glomerular Filtration Flashcards
3 main functions of the kidney
Filtration - the formation of an essentially protein-free filtrate
Reabsorption - Substances that the body wants are reabsorbed
Secretion - Substances may be specifically removed from the body in this way.
What substances are reabsorbed
NaCl
Water
Amino Acids
Sugars
What substances are excreted
Organic ions
Drugs
K+ and H+
Where are NaCl, water, amino acids and sugars reabsorbed
The proximal tubule
Where are NaCl and water reabsorbed only
The distal tubule
Where are orgainc ions and drugs secreted
Proximal tubule
Where are H+ and K+ secreted
The distal tubule
What happens at the thin loop
Passive water and NaCl exchange
Where does the blood go after the glomerulus
The efferent arterioles ->peritubular capillaries -> the renal vein
How much of the total blood volume does plasma make up
~55%
Normal Glomerular Filtration Rate (GFR)
125ml/min
How much of the renal plasma becomes glomerular filtrate
~19%
What two forces is Glomerular Filtration dependent on
balance between hydrostatic forces and oncotic pressure forces
What force favours filtration and what force favours Reabsorption
Hydrostatic forces = Filtration
Oncotic pressure forces = Reabsorption
What effects a particles ability to filtered
Size, shape and charge
“Golden rule of circulation”
If you have a high resistance, hydrostatic pressure upstream is increased, while the pressure downstream is decreased.
Where are afferent and efferent arterioles in relation to the glomerulus ie before or after
Afferent = before Efferent = after
What is the effect of increased afferent arterioles resistance
Decreased; Renal blood flow, capillary blood pressure and GFR
Increased blood flow to other organs
What is the effect of increased resistance of efferent arterioles
Decreased RBF
Increased capillary blood pressure and GFR
What is the effect of decreased afferent arteriole reistance
Increaed; RBF, capillary blood pressure and GFR
What blood pressure is the glomeruli’s autoregulation effective over
60-130mmHg
What happens when blood pressure reaches 50mmHg
No more filtration
What’s the response to increased mean arterial pressure
Constriction of afferent arterioles
What’s the response to decreased mean arterial pressure
Dilatation of afferent arterioles
What blood vessels are responsible for Reabsorption
Peritubular capillaries
Pressure in peritubular capillaries
~15mmHg
What is different about the blood in the efferent arterioles and the peritubular capillaries compared to systemic circulation
It has a higher concentration of plasma proteins
What is different about the blood in the efferent arterioles and the peritubular capillaries compared to systemic circulation
It has a higher concentration of plasma proteins (therefore a higher oncotic pressure?) Due to this difference Reabsorption is favoured
How much water, Na+, glucose and urea are reabsorbed
Water = 99% Na+ = 99.55 Glucose = 100% Urea = 50% Mainly at the proximal convoluted tubule
