Renal physiology Flashcards
What are the functions of the renal system?
Regulation of water, ions, acid-base; removal of metabolic waste products from blood (urea and creatine); removal of foreign chemicals fro the blood; gluconeogenesis during prolonged fasting; production of hormones/ enzymes
What hormones/enzymes does the renal system produce?
Erythroprotein, controls RBC production; renin, controls formation of angiotensin; conversion of 25-hydroxyvitamin D –> 1,25-dihydroxyvitamin D, influences Ca2+ balance
What are the two (VERY GENERAL) sections of the nephron?
Renal corpuscle and tubule
How much of plasma is filtered into Bowman’s?
~20%
How is the glomerulus/Bowman’s capsule specialised for its function?
Has arterial afferent and efferent flow, creating high blood pressure; very porous glomerulus to allow fluid and other ions to be squeezed out of blood; podocytes with slite allow additional filtration
What is in the filtrate that enters the Bowman’s space?
Na+, Cl-, K+, H2O, glucose, amino acids
What occurs at the proximal convoluted tubule?
Reabsorption by active transport; Na+, glucose, small H2O
What occurs at the Loop of Henle?
Na+, K+ and Cl- reabsorbed at ascending limb by active transport; medulla becomes hypertonic; water leaves descending limb down water potential gradient
What occurs at the distal convoluted tubule?
Further reabsorption occurs
What occurs at the collecting duct?
ADH acts to allow more water to be reabsorbed by mobilisation of aquaporins
What parts of the nephron are within the medulla?
Glomerulus, Bowman’s capsule, PCT, some of Loop of Henle, DCT, some of collecting duct
What parts of the nephron are within the cortex?
Some of Loop of Henle and collecting duct
What are the three basic process of the nephron?
Glomerular filtration, tubular secretion, tubular reabsorption
How does the kidney differentially handle substances?
Depending on necessity to body, may be fully excreted, partially, or fully reabsorbed
How is the amount excreted by the kidneys calculated?
Amount filtered + amount secreted - amount reabsorbed
Why do plasma proteins remain in plasma?
To maintain osmotic pressure
What disease is kidney damage often found in?
Diabetes and hypertension. If left untreated, can lead to end-stage renal disease and renal failure
What is glomerular filtration governed by?
Starling’s forces: hydrostatic pressure difference vs protein concentration difference (filtration vs osmotic force). Thus can be controlled by vascular changes
What is tubular reabsorption?
Can be active or passive; paracellular transport occurs b/w cells; mostly seen with ions; begins as soon as filtrate enters tubule cells
What is tubular secretion?
H+, K+ or organic ions from peritubular capillaries into tubular lumen; important mechanism for disposal of drugs and drug metabolite/ undesired substances or end products that have to reabsorbed by passive process (urea, uric acid)/ excess K+/ controlling blood pH
What is renal clearance?
Volume of plasma that is cleared of a substance in one minute
What is the equation for renal clearance?
([substance] in urine*flow rate of urine formation)/[substance] in plasma
How can renal clearance be measured?
Insulin as is freely filtered, not reabsorbed or secreted; creatinine is less accurate as secreted in small amounts
