Renal Clearance Flashcards
What is the extraction ratio in renal physiology?
The fraction of a substance removed from the plasma in one pass through the kidneys.
How is renal blood flow (RBF) calculated using extraction ratio?
RBF = Effective Renal Plasma Flow (ERPF) / Extraction Ratio.
What is the principle of dialysis?
Diffusion of solutes across a semipermeable membrane along a concentration gradient.
What is the semipermeable membrane used in dialysis?
Artificial or natural membranes that allow selective passage of small molecules but not large proteins or cells.
Why does angiotensin II increase sodium reabsorption?
It stimulates Na⁺/H⁺ exchange in the proximal tubule and increases aldosterone secretion.
Where does angiotensin II promote sodium reabsorption?
In the **proximal tubule
Why is the filtrate at the macula densa a measure of sodium levels in the body?
Macula densa detects NaCl concentration in the distal tubule and regulates renin release.
How is sodium reabsorbed in the nephron?
- Proximal tubule: Na⁺/H⁺ exchanger
What does it mean if a substance’s clearance is higher than inulin but lower than PAH?
The substance is filtered and partially secreted, but not fully excreted in one pass.
Why does PAH clearance (600 mL/min) indicate active secretion?
PAH is filtered and actively secreted into the tubule, allowing almost complete removal in one pass.
A patient with kidney disease has decreased creatinine clearance. What does this indicate?
Decreased glomerular filtration rate (GFR) and impaired kidney function.
A person with high plasma urea but normal urea clearance is suspected of dehydration. Why?
Dehydration reduces plasma volume, increasing plasma urea concentration, but renal clearance remains normal.
How does a diuretic affect sodium clearance?
Diuretics increase sodium clearance by reducing Na⁺ reabsorption, leading to increased urine output.
Can diuretics be used to flush toxins?
Yes, diuretics increase urine production, which can help eliminate some toxins, but they are not effective for all toxins.
What are the major steps of the micturition reflex?
- Bladder fills, stretch receptors activate.
- Afferent signals go to the spinal cord.
- Parasympathetic nerves contract the detrusor muscle.
- Internal urethral sphincter relaxes.
- Voluntary control via pudendal nerve relaxes the external urethral sphincter.
Which nerve provides voluntary control over micturition?
Pudendal nerve controls the external urethral sphincter.
