RENAL BLOOD SUPPLY & FLOW Dr. Mahmud Abuauba MBChB, DCH, MD, PhD Consultant Pediatrician & pediatric Nephrologist Assistant Professor of Pediatrician Zawia Kidney Center 5 th May 2018
برعاية مركز عالج أمراض الكلى-الزاوية
RENAL BLOOD SUPPLY
RENAL BLOOD SUPPLY Both kidneys receive approx. 21% (20 25%) of cardiac output, at rest 1200 ml/min (1000 1500 ml/min) = High blood supply ~ 4 ml/g/min of kidney tissue; why? Not only, to supply oxygen & nutrients, etc. To control precisely fluid, electrolytes & acid-base balance To remove waste products rapidly
RENAL BLOOD SUPPLY Renal oxygen comsumption is high ~6 ml/100g/min, which correlates with Na-K pump & renal blood flow Entire blood circulates through the glomeruli every 4-5 min
RENAL ARTERY Each kidney receives a single main renal artery (Rt &Lt) From abd. Aorta at Rt angle, at L 2 Lt RA is shorter In about 30%, accessory RA or abberent RA, no veins, lower pole Main RA gives branches to adrenal gland, renal pelvis, ureter, renal capsule & perirenal fat
Left renal vein is longer than the right renal vein
Division arteries Each main RA upon or just arrival to hilum divides into two divisions or branches: Anterior branch to anterior part of kidney Posterior branch to posterior part of kidney Supplying five vascular segments
Segmental arteries Pos. division supplies only pos. segment Ant. division to four segments; apical, upper, middle & flower While still in hilum, these 2 branches give rise to 5 segmental arteries (5) with each one supplies one segment No anastomoses be segmental As Have surgical importance, end As
LOBAR ARTERY Initial branch of Seg. A is lobar As before entry into renal substance One for each renal pyramid or renal lobe Just before entry into renal substance, gives 2-3 interlobar As That run between renal pyramids towards the cortex
ARCUATE ARTERY I At corticomedullary border, interlobar artery divides into arcuate arteries at right angle Interlobular As arise from arcaute arteries at right angle Interlobular arteries form borders of renal lobule
ARCUATE ARTERY II Ascend toward the renal capsule, end as capsular plexus No anastomoses between arcaute As, Arcuate arteries are considered as end arteries Arcuate A ends as interlobular A
Afferent glomerular arteriole Interlobular As run in center of cortical labyrinth They form the borders of renal lobules Each gives rise to many AGAs AGAs are short, stright, enter renal corpuscle at vascular pole Each AGA divides into a tuft of capillaries forming glomerulus
Renal Corpusle
GLOMERULUS Each afferent glomerular arteriole divides into 3-5 branches then a tuft of capillaries (20-40 loops) Forms the glomerulus Capillaries coalesce again to form efferent glomerular arteriole EGA is longer & narrower, why AGA is shorter, striaght & wider
PERITUBULAR CAPILLARIES EGA of cortical nephrons breaks into another set of capillaries called peritubular capillary plexus Surrounds PCT, DCT & CCT Supplies entire cortical labyrinth, except glomerulus Epo, 90% in peritubular capillary endothelial cells, 10% in the liver
Vasa recta I EGA of juxtamedullary nephrons breaks into another set of thin & long capillaries called vasa recta Accompanies Henel s loop Vasa recta formed of: arteriole recta 12-25 descending branches vena recta, 12-25 ascending branches
Vasa recta II Arteriole recta has nonfenestrated endothelial cells, single layer Vena recta has fenestrated endothelial cells Supply blood to medulla (1-3%), for nutrients & O2 Form basis of CCE & CCM All endothelial cells of nephrons are fenestrated, except descending vasa recta
VENOUS RETURN Venous end of PTCP convey to form interlobular veins Capillaries of outer cortex & renal capsule converge to form stellate veins which empty into interlobular veins Then follows arterial system
VENOUS RETURN There are anastomoses There are no segmental or lobar V Unite at hilum, renal vein, Rt & Lt IVC to heart
RENAL BLOOD SUPPLY Has two capillary sets Glomerulus & PTCP seperated by EGA This arrangement helps to regulate glomerular filtration Glomerular hydrostatic pressure is 60 mm Hg & PTCP is 13 mm Hg glomerular filtration & tubular reabsorption
RENAL BLOOD SUPPLY Surface area of renal capillary = SA of tubules= 12 m 2 Total SA for filtration = 0.8 m 2 Volume of blood in capillaries is 30-40 ml
NORMAL CIRCULATION Heart Veins Arteries Venules Arterioles Capillaries
RENAL CIRCULATION Veins Heart arteries Arterioles Venules glomerulus PTC arterioles
RENAL BLOOD FLOW
RENAL BLOOD FLOW
Renal Blood Flow Effective renal plasma flow (ERPF)= CPAH = UPAH X V = 585 ml /min PPAH TRPF = / extraction ratio = 585/ CPAH 0.9= 650 ml/min TRBF = TRPF = 1200 ml/min 1 - HCT
AUTOREGULATION A mechanism by which RBF & GFR remain constant despite change in RABP (75 160 mmhg), WHY? If GFR is 125ml/min so 180L/day is formed where 178.5L/day reabsorbed & 1.5L/day is urine, at BP ~100mmHg If BP rises from 100 to 125 mm Hg so GFR rises from 180 to 225L/day, 178.5L/day reabsorbed & 46.5L/day is lost, fatal
THANKS FOR ATTENTION