Dr./ Hussein F. Sakr
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Renal Physiology
Anatomy of the kidney
• The kidney is a retroperitoneal organ, about 150 gm in weight (2 kidneys 0.5 % of the body weight).• It is covered by a renal capsule
and renal fascia.
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Structure of the kidney• The kidney is divided into an outer
cortex and inner medulla.- The medulla is composed of renal pyramids, separated by renal columns.- The renal pyramids empty urine into the calyces that drain into the renal pelvis. From there urine flows into the ureter and is transported to the bladder to be stored.
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General function of the kidney
• Regulate ECF volume.• Regulation of electrolytes.• Regulation of arterial blood pressure.• Regulation of pH (acid-base balance).• Excretion of waste products.• Endocrinal function (renin- erythropoietin- active vitamin D).• Degradation of hormones.
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Functional organization of the kidney
• Renal cortex:Red and dotted.Contains glomeruli.Contains proximal tubules,
distal convoluted tubules and cortical collecting duct.
• Renal medulla:Pale and radial.Contains renal pyramids which
contain minor calyces that unite to form major calyces.
Contains loop of Henle and medulary collecting ducts.
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Blood supply of the kidney
• The kidneys receives its blood through the renal artery.• The renal artery is divided into
anterior and posterior branches each one divides into 5 segmental branches interlobar arcuate interlobular afferent glomerular capillaries efferent arteriole.
• Efferent arteriole peritubular capillary and vasa recta interlobular vein interlobar vein segmental renal vein IVC.
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Nephron it is the structural and functional unit of the kidney
Renal corpuscle • Formed of:
1) glomerulus: 20-40 loop of capillaries between afferent
and efferent arteriole.2) Bowman’s capsule: which is
the blind end of the proximal tubule.
Renal tubules• Formed of:
1) Proximal tubule.2) Intermediate tubule (loop of
Henle).3) Distal tubule (distal
convoluted tubule, connecting tubule and collecting duct.
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Types of nephrons
Superficial cortical • 85-90 % .
• Glomerulus in the outer 2/3 of the cortex.
• Loop of Henle is formed of DLH and ALH.
• Loop of Henle makes a bend at the junction between outer and inner
medulla.• Small in size with low capacity to
reabsorb salt and water.
Juxta medullary • 10-15 %.
• Glomerulus in the inner 1/3 of the cortex.
• Loop of Henle is formed of DLH , thin ALH and thick ALH.
• Loop of Henle makes a bend at the tip of inner medulla.
• Large in size with high capacity to reabsorb Na and water.
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Types of nephrons
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Juxta-glomerular apperatus
• It is system formed of modified:1) Macula densa cells.2) Juxta- glomerular granular
cells.3) Extra-glomerular mesengial
cells.
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Macula densa cells
• Modified tubular epithelial cells.• Present at the transitional zone between thick ALH and DCT.• Monitor Na and chloride concentration in the tubular fluid.
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Juxta glomerular granular cells
• Present in the wall of the afferent arteriole.• Smooth muscles with epitheliod apperance.• Forms , stores and secretes renin.• Contains B1 adrenergic receptors.• Acts also as baroreceptors.
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Extraglomerular mesengial cells
• It is a continuation of the intraglomerular mesengial cells.• It is in direct contact with the macula densa and juxtaglomerular
granular cells.
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Stimuli for renin release
• Sympathetic stimulation.• Renal ischemia.• Decrease Na+ and Cl- concentration in the tubular fluid.
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Mechanisms of stimulation:
Renin releaseIn cases of hemorrhage
with decreased circulating blood volume
stimulation of low and high pressure
baroreceptors located in the great vessels of the thorax stimulation of
the sympathetic nervous system stimulation of B receptors on JGG cells
renin release
With renal artery stenosis or thrombosis decreased renal perfusion pressure
stimulation of the juxta glomerular granular cells
renin release.
Decreases Na & Cl concentration of the
tubular fluid stimulation of the macula densa that
stimulates the JGGcells via Prostaglandins renin
release.
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Renin Angiotensin Aldosterone system
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Inhibitors of renin release
• Aldosterone .• Atrial Nariuretic Peptide (ANP).• AII.• Hypernatremia.
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Function of the renin angiotensin system
Salt and water retention 1- angitensin II increases Na
reabsorption from proximal tubules.
2- AII stimulates the zona glomerulosa of the adrenal cortex to secrete aldoseterone that increases Na reabsorption from distal tubules.
Vasoconstriction 1- arteriolar constriction
increasing the afterload (arterial blood pressure).
2- Venoconstriction increasing the preload (venous return).
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Pharmacological Inhibitors of the RAAS
• Angiotensin converting enzyme inhibitors: decreased the formation of AII.• Angiotensin II blockers: decreased aldosterone release.• B- blockers.
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