Lecture 35/36 Flashcards
What is the renal blood supply line an how much?
Renal blood supply is 20-25% of the cardiac output, (1-1.2L/min), this high flow acts for filtration raather than for metabolism as is typical. It occurs via renal arteries going into afferent arterioles then glomerula capillaries then efferent arterioles then the peritubular capillaries and renal vein.
Why is blood supply to the renal pathway regulated and how?
The blood supply of the renal system is regulated so that filtration is relatively constant despite blood pressure variations, this can be intrinsic (autoregulation): myogenic (mechanical receptors act on the vascular smooth muscles in the afferent arteriole) and tubuloglomerular feedback via the juxtaglomerular apparatus, or extrinsic (outside the kidney) via the sympathetic vasoconstrictor nerves and angiotensin II.
The juxtaglomerular appartus is a specialised zone in every nephron which is found where the distal convoluted tubule lies against the afferent arteriole, both have specialised cells (macula densa, a chemoreceptor (sodium) detector) and control glomerular filtration rate and stabilises blood pressure.
What is glomerular filtration rate and filtration fraction?
Glomerular filtration rate it the amount of fluid filtered per unit time, normally 180 L/day or 125 ml/minute. Its tightly regulated, has some variation between people, has 70 ml/min/m2 bosy surface area. It declines slowly from age 30 and a single nephron does 60 microletres per day. Only roughly 20% of plasma is filtered, this ratio of blood that reaches the kidney that gets filtered in the glomerulus is the filtration fraction.
What layers does the filtration barrier have? What do they seperate based on?
The filtration barrier is found in the glomerulus and it where filtration occurs, it has three layers: the capillary endothelium (a charged endotehlium), the basement membrane (three layers, seperates based on different sizes and charge) and epithelial podocytes (filters by size and charge.
What is glomerular filtration aided by? What are some common pressure values?
Glomerular filtration is facillitated by pressure gradient between the glomerular capillary and bowmans space, the permeability of glomerular capillary and the surface area of the glomerular capillary. Renal blood flow (glomerular hydrostatic pressure) provides about 60 mmHg and capsular osmotic pressure (typically 0, due to it being the same as in the blood), these both moe fluid out of the glomerulus. The glomerular osmotic pressure (30mmHg) and capsular hydrostatic pressure (20 mmHg) move fluid into the glomerulus.
What is the filtered load and what is the equation?
The filtered load is the amount of a particular substance that is filtered per minute and is given by GFR (glomerular filtration rate) x solute concentration.
