egional Circulation II (renal, fetal) Assoc. Prof. MUDr. Markéta Bébarová, Ph.D. Department of Physiology, Faculty of Medicine, Masaryk University This presentation includes only the most important terms and facts. Its content by itself is not a sufficient source of information required to pass the Physiology exam. Renal Circulation Renal Circulation • main functions of kidneys - control of composition and volume of extracellular fluid, detoxification • High filtration rate requires an adequate blood supply! - kidneys form only -0.4 % of the body weight - blood flow 1.2 l/min, -25% of cardiac output • distribution of blood flow is irregular, the most flows through cortex (glomeruli - filtration) - cortex: 5.3 ml/g/min - medulla - outer zone: 1.4 ml/g/min ^» - medulla - inner zone: 0.4 ml/g/min (v, Renal Circulation Cortical radiate vein Cortical radiate artery Arcuate vein Arcuate artery Interlobar vein Interlobar artery Segmental arteries Renal vein Renal artery Renal pelvis Ureter Renal medulla Renal cortex (a) Frontal section illustrating major blood vessels C 2013 Ptanon Education Ire Aorta I Renal artery 1 Segmental artery I Interlobar artery I Arcuate artery I Cortical radiate artery t i---- i i I Afferent arteriole Inferior vena cava Renal vein Interlobar vein í Arcuate vein í Cortical radiate vein -f Peritubular capillaries -or vasa recta í Efferent arteriole Glomerulus (capillaries J Nephron-associated blood vessels (see Figure 25.7) (b) Path of blood flow through renal blood vessels http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/chap25.htm Mr coiTAS ^ Cortical nephron Juxtamedullary nephron • Short nephron loop • Long nephron loop • Glomerulus further from the cortex-medulla junction • Glomerulus closer to the cortex-medulla junction • Efferent arteriole supplies peritubular capillaries * Efferent arteriole supplies vasa recta F renal cortical tissue (180X) © 2013 Pearson Education. Inc. http://classes.midlandstech.edu/carterp/Courses/bio211/chap25/chap25.htm Renal Circul • v. aff., v. eff. • entry/exit of high pressure glomerular capillary system • glomerular blood flow = ■ Glomerular Glomerular hydrostatic colloid osmotic pressure pressure (60 mm Hg) (32 mm Hg) t Bowman's capsule pressure (18 mm Hg) P " P 1 v.a. 1 v.e. Guyton & Hall. Textbook of Medical Physiology RV.a. + Rv.e. + • t resistance in vas aff. or vas eff. -> I the renal blood flow (if the arterial pressure is stable) • regulate the glomerular filtration pressure:_ constriction of vas aff. -> I glomerular pressure -> I filtration constriction of vas eff. ->■ t glomerular pressure ->• t filtration Renal Circulation • Regulation of renal blood flow: 1) Myogenic autoregulation 2) Neural regulation 3) Humoral regulation Renal Circulation Regulation of renal blood flow: 1) Myogenic autoregulation - dominates - provides stable renal activity by maintaining stable blood flow at varying systemic pressure (stable glomerular pressure and, thus, also stable glomerular filtration rate) 800 r 600 J 400 E 200 Renal blood flow Glomerular filtration 70 140 210 Arterial pressure (mm Hg) Ganong's Review of Medical Physiology, 23rd edition Air Renal Circulation • Regulation of renal blood flow: 2) Neural regulation - conformed to demands of systemic circulation - renal blood flow forms 25% of the cardiac output, thus, it considerably influence BP - sympathetic system - norepinephrine light exertion (both emotional and physical) + upright body posture -> t sympathetic tone -> t tone of v. aff. and eff. ->• I renal blood flow but without 4- GFR (t FF) higher t of sympathetic tone - during anesthesia and pain - GFR may already i Renal Circulation • Regulation of renal blood flow: 3) Humoral Regulation - contribute to regulation of systemic BP and regulation of body fluids - norepinephrine, epinephrine (from adrenal medulla) -> constriction of aff. and eff. arterioles -> I renal blood flow and GFR in agreement with t activity of sympathetic system (small impact with the exception of serious conditions, for example serious bleeding) Renal Circulation • Regulation of renal blood flow: 3) Humoral Regulation - contribute to regulation of systemic BP and regulation of body fluids - endothelin constriction of aff. and eff. arterioles ->• 4- renal blood flow and GFR released locally from the impaired endothel (physiological impact - hemostasis; pathologically increased levels at the toxemia of pregnancy, acute renal failure, chronic uremia) enal Circulation • Regulation of renal blood flow: 3) Humoral Regulation - contribute to regulation of systemic BP and regulation of body fluids - NO (from the endothel) continual basal production -> vasodilation in the kidney -> stable renal blood flow and GFR - prostanglandins (PGE2, PGI2), bradykinin -> vasodilation - minor impact under physiol. cond. decrease the effect of vasoconstrictive substances which reduce marked I of renal blood flow and GFR non-steroidal anti-inflammatory agents during stress (surgery, I fluid volume) may -> notably 4 GFR Renal Circulation • Regulation of renal blood flow: 3) Humoral Regulation - contribute to regulation of systemic BP and regulation of body fluids - Renin-angiotensine Gomerulus system Ganong's Review of Medical Physiology, 23rd edition Renal Circulation Renin-angiotensine system i Ť Na+in plasma Juxtaglomerular apparatus BP ^ Jp> sympathetic activity (P rec.) Angiotensinogen i- Renin Angiotensin I I Angiotensin- Increased renal arterial mean pressure, decreased discharge of renal nerves Increased extracellular fluid volume converting enzyme Angiotensin II Aldosterone vasoconstriction thirst, ADH Adrenal cortex Decreased Na+ (and water) excretion Ganong's Review of Medical Physiology, 23rd edition \Alr Renal Circulation PPAH = 0.01 mg/ml - Determination of renal plasma flow velocity (RPF) Clearance of a substance which is fully cleared from plasma in glomerulotubular apparatus. PAH (paraaminohippuric acid) cleared by 90% RPF = 5.85 x 1 mg/min 0.01 mg/ml = 585 ml/min Renal plasma flow V- Renal venous PAH = 0.001 mg/ml UPAH = 5.85 mg/ml V = 1 ml/min Guyton & Hall. Textbook of Medical Physiology (in juxtamedullar nephrons, vasa recta additionally originate from v. efferens - not in contact with proximal and distal tubuli no excretion of substances) I Renal Circulation PPAH = 0.01 mg/ml - Determination of renal plasma flow velocity (RPF) Clearance of a substance which is fully cleared from plasma in glomerulotubular apparatus. PAH (paraaminohippuric acid) cleared by 90% RPF = 5.85 x 1 mg/min 0.01 mg/ml = 585 ml/min Renal plasma flow V- Renal venous PAH = 0.001 mg/ml UPAH = 5.85 mg/ml V = 1 ml/min Guyton & Hall. Textbook of Medical Physiology Correction to the extraction ratio of PAH (EPAH): i- Ppah " V PAH PAH = 0.9 PAH ^ r^r- 585 ml/min . -> RPF =-= 650 ml/min 0.9 Ait Fetal Circulation Fetal Circulation Left atriu Superior vena cava 62°/< o Ductus arteriosus Foramen ovale placenta, umbilical vein liver, ductus venosus crista dividens, foramen ovale blood supply of the head and upper limbs v. cava superior and inferior the right ventricle ductus arteriosus aorta - the blood supply of the lower part of body + 60% of the cardiac output is directed to placenta Ganong's Review of Medical Physiology, 23rd edition Pulmonary artery Left ventricle To placenta Fetal Circulation fetal haemoglobin (higher affinity to oxygen) • short-period hypoxia • longer hypoxia g • thick muscle wall of | umbilical vessels a (sensitive contractile reaction to many stimuli -injury, hypoxia, sympathomimetics, etc.) 10 20 30 40 50 60 70 80 90 100 Po2 (mm Hg) Ganong's Review of Medical Physiology, 23rd edition Fetal Circulation Left atrium Superior vena cava Ductus arteriosus Foramen ovale Changes after birth Closure of umbilical vein - sudden t of peripheral resistance and blood pressure - contraction of musculature of ductus venosus and its closure The first inspiration (due to asphyxia and cooling of the body) - I resistance of the lung bloodstream - much more blood into lungs Ganong's Review of Medical Physiology, 23rd edition Pulmonary artery Left ventricle Portal vein Umbilical vein a • From '. placental To placenta Fetal Circulation Changes after birth Decrease of pressure in right atrium and its increase in left atrium due to: - t filling of left atrium by the blood from lungs - I venous return to right atrium due to closure of umbilical vein - left ventricle works against t pressure in aorta Closure of formanen ovale Closure of ductus arteriosus Left atrium Superior vena cava Foramen ovale Ductus arteriosus Pulmonary artery Left ventricle Portal vein Umbilical vein a From placental To placenta Ganong's Review of Medical Physiology, 23rd edition \Alr Fetal Circulation Placenta Body L heart DA (J) - Lungs i 1- R heart FETUS Left atrium FO DA Body L heart Lungs R heart NEWBORN Body L heart Lungs R heart Superior vena cava Foramen ovale Portal vein Umbilical vein A left and right heart work in parallel From placental To placenta Ductus arteriosus ADULT all connected in series _ Ganong's Review of Medical Physiology, 23rd edition Pulmonary artery Left ventricle