Renal Physiology Lecture 1 - Teel Flashcards
Afferent / Efferent arteriole
Afferent arteriole: brings blood into glomerular capillaries. (a comes first)
Efferent arteriole: blood leaves glomerular capillaries.
podocytes
Mesangial cells
Podocytes: specialized cells that wrap around the glomerular capillaries
Mesangial cells: located in mesangium, gives structure to capillaries so they do not freely float around. Exhibit phagocytosis, secrete prostaglandins / pro-inflammatory cytokines.
Basic elements of Renal Function, in order
1.) Filtration: From Glomerular capillaries to Bowman’s capsule
2.) Reabsorption: From Tubule into peritubular capillaries
3.) Secretion: From peritubular capillaries to Tubule
4.) Excretion: end of collecting duct emptying into pelvis / kidney.
Filtration - Reabsorption + Secretion.
These terms are always from the arteriole point of view
Mass balance
Substances that is in the urine and blood is equal to what it was in the afferent arteriole. (Beginning concentration is equal to end concentration)
Input = Output
Filtered Load:
GFR (glomerular filtration rate) x plasma concentration
Clearance
Volume of plasma that has been completely cleared of some substance. Secretion enhances clearance, reabsorption does opposite.
Equation:
X = (urine conc. of substance X) (urine flow rate) / (plasma concentration of substance X)
UV/P
Nervous system relations to urinary system
Sympathetic: Bladder / sphincters innervated, via a and B receptors
Parasympathetic: Bladder also innervated, via muscarinic receptors
Therefore emotional state can affect bladder (wetting urself when nervous)
Pacemaker cells in the Renal Pelvis
Peristaltic waves in ureter, carries wave frequency. Very slow waves, 2-4 min.
Micturition reflex
How to urinate
Initiated by stretch receptors that are sensitive to urine volumes beginning around 150 ml
Urine volumes >400 ml cause an abrupt increase in pressure and strong sensations of bladder fullness.
Voidness is accomplished by relaxation of external / internal sphincters and contractions of detrusor and abdominal muscles.
Glomerular Filtration rate average
How to measure this
About 180 L/day or 125 ml/min. Filtrate = similar in composition to plasma without the blood cells and protein.
Most accurate way to measure: clearance of inulin. (body does not produce inulin)
General method: clearance of creatinine.
Clearance ratio
Cx / Cin
(Clearance of what ur measuring, x) / (Clearance of inulin, which is 100% filtration)
Ratio of 1 = x = clearance of inulin
Ratio < 1 = x not completely filtered, or is reabsorbed. or both.
Ratio > 1 = x is secreted.
