Physiology of Micturition & Assessment of Renal Function, Urea, Creatinine and GFR Flashcards
What is the equation used to calculate plasma clearance?
[Ux] V/[Px]
U= urine concentration of X V= urine flow rate P= plasma concentration of X
Why is inulin the gold standard for measurement of GFR?
Freely filtered in glomerulus
Neither reabsorbed or excreted
Not metabolised by the kidney
Doesn’t interfere with renal function
What is a “normal” value for GFR in males?
125mls/min
What can be used in practice as a substitute for inulin?
51Cr-EDTA
What factors can affect serum creatinine?
Muscle mass
Dietary intake
Drugs
What is para-amino-hippuric acid (PAH) used to measure?
Real plasma flow (RPF)
How does urine move from the kidneys to the ureters?
Peristaltic contraction
Describe the detrusor muscle?
Smooth muscle arranged in spiral, longitudinal and circular bundles
What type of epithelium is found in the bladder?
Transitional epithelium
How does parasympathetic innervation affect the bladder?
Increases contraction of detrusor muscle
How does sympathetic innervation affect the bladder?
Inhibits bladder contraction
Closes internal urethral sphincter
Prevents reflux of semen into the bladder during ejaculation
How do the somatic motorneurones affect the bladder?
Innervate skeletal muscle that forms the external urethral sphincter
What happens to the stretch receptors as the bladder fills?
Stretch receptors are increasingly stimulated until their output becomes great enough to cause bladder contraction
What are the 3 main abnormalities of micturition?
Interruption of afferent nerves
Interruption of both afferent and efferent nerves
Interruption of facilitatory and inhibitory descending pathways from the brain
