Renal Physiology Flashcards
What is the kidney cardiac output?
5 L/min
What is the renal blood flow?
1 L/min
What is the kidney urine flow?
1 ml/min
What is the order of renal blood supply?
AA
↓
Renal artery
↓
Segmental artery
↓
Interlobar artery
↓
Arcuate artery
↓
Interlobular artery
↓
Afferent arteriole
↓
(Nephron)
Glomerular Capillary
↓
Efferent arteriole
↓
Peritubular Capillary
↓
Vasa recta
↓
Interlobular veins
↓
Arcuate veins
↓
Interlobar veins
↓
Renal veins
↓
IVC
What is the distal part of the nephron (tubule) responsible for?
Secretion and reabsorption
What 5 factors determine the crossing of the filtration barrier?
- Pressure
- Size of the molecule
- Charge of the molecule
- Rate of blood flow
- Binding to plasma proteins e.g. calcium, hormones such as thyroxine
In the filtration barrier what molecules can pass freely?
Small molecules and ions up to 10kDa
e.g. glucose, uric acid, potassium, creatinine
What does the negative charge in glomerular basement membrane cause?
Fixed negative charge in glomerular basement membrane repels negatively charged anions
What is the main urinary protein?
Albumin
What is the molecular weight of albumin?
Around 66kDa
What charge is albumin and what does this mean?
Negatively charged, cannot easily pass into the tubule
What can damage to the filtration barrier lead to?
Can lead to protein leak and a condition known as nephrotic syndrome
What is the glomerular filtration rate?
The filtration volume per unit time (minutes)
What is autoregulation?
Renal blood flow, capillary pressure and GFR maintained almost constant over systemic mean arterial pressure range 90-200 mmHg
Where does autoregulation occur?
In denervated kidneys & in isolated perfused kidneys ∴ not dependent on nerve supply or on blood-borne substances
What is the mechanism of autoregulation?
Pressure within afferent arteriole rises
Stretches vessel wall
Triggers contraction of smooth muscle
Arteriolar constriction
What does autoregulation prevent?
Prevents an increase in systemic arterial pressure from reaching the capillaries
What is the GFR of individual nephron regulated by?
By the rate at which filtered fluid reaches the distal tubule
What do the cells of macula densa (distal tubule) detect?
NaCl arrival
What do macular densa cells release?
Release prostaglandins in response to reduced NaCl delivery
This acts on granular cells, triggering renin release, activating the renin-angiotensin system
What is renal clearance?
The volume of plasma from which a substance is completely removed by the kidney per unit time (usually a minute)
Where does filtration occur?
Occurs at the glomerulus from capillaries into Bowman’s space across a barrier of several layers
What is GFR determined by?
Net filtration pressure
Permeability of filtration barrier
Surface area available for filtration
What is GFR maintained by?
Autoregulation and tubuloglomerular feedback
