Glomerular filtration Flashcards
What is the GFR/ day?
180L/day
What are the basic renal processes?
Filtration
Reabsorption
Secretion
What % of CO do the kidneys receive?
20-25%
What is the GFR/min?
125ml/min
What forces favour filtration?
Hydrostatic pressure
Which forces favour reabsorption?
Oncotic pressure
Which molecules are filtered freely?
Na, K, Cl, h2O, Urea, Glucose
Which molecules in the plasma are not filtered at the glomerulus?
RBCs
Albumin
What is the structure of the afferent arteriole? Function?
Short & wide
Reduces resistance to flow
What is the structure of the efferent arteriole? Function?
Long & narrow
High post-capillary resistance
What process occurs at the glomerular capillaries? What force allows this?
Filtration
High hydrostatic pressure
What is the glomerular capillary pressure determined by?
The diameter of the afferent & efferent arterioles
What are the extrinsic factors which control the diameter of glomerular capillaries?
Sympathetic nerves
Circulating adrenalin
Angiotensin II
What will happen to the glomerular capillary pressure and GFR if afferent arteriole resistance increases?
Decreases
What will happen to PGc and GFR is efferent arterioles are constricted?
Increases
What does autoregulation allow the control of in the kidneys?
Intrinsic control of glomerular capillary pressure, maintaining BP & GFR
What is the auto regulatory range that Mean Arterial Blood Pressure is maintained within? Advantages?
60-130mmHg
Maintains GFR over a range of BPs
In what situations can auto regulation be over ridden?
Haemorrhage
How much urine is excreted per day?
1-2L/day
What is reabsorption driven by? Why? Where does this occur?
Oncotic pressure
High concentration of plasma proteins
Peritubular capillaries
What % of water, glucose, Na & urea filtered at the glomerulus is reaborbed?
Where?
99% 100% 99.5% 50% Proximal convoluted tubule
