Introduction to Renal Physiology Lecture Notes PDF

Introduction To Renal Physiology Prof. Dr. Mervat El-Saka Renal System Functional Anatomy of the Kidney The kidney consists of 2 distinct zones Red Granular...

Introduction To Renal Physiology Prof. Dr. Mervat El-Saka Renal System Functional Anatomy of the Kidney The kidney consists of 2 distinct zones Red Granular An outer cortex An Inner medulla Paler Striated  Red 1- An outer cortex Functional Granular Anatomy of the Kidney Paler 2- An inner medulla Striated  Medulla is formed of Pyramids (10-15 triangular-shaped) Apexes of Pyramids form the renal papillae which drain into the calyces.  Nephrons The nephron is the functional unit of the kidney (Each kidney consists of about 1 million of nephrons. Each nephrons works independently to produce urine  Components of renal nephron 1- Glomerulus 2- Renal tubule.  The glomerulus: It consists of capillary network lying between two arterioles afferent & efferent.  Blood inters the glomerulus via an afferent arteriole and leaves it via a narrower efferent arteriole.  It invaginates the upper blind end of the renal tubule forming a Bowman's capsule. Bowman's capsule consists of: A. Inner visceral layer: closed to the capillary network of glomerulus. B. Outer parietal layer continuous with the proximal convoluted tubules.  Both glomerulus & Bowman's capsule are called the malpighian (renal) corpuscle. which is located in the cortex. Glomerulus & Bowman’s capsule  Renal tubule consists of 1- Proximal 3-Distal 2- Loop of convoluted convoluted Henle tubules (DCT) tubule (PCT)  Renal tubule The renal tubule: concerned with urine formation, consists of three parts: 1. Proximal convoluted tubule (PCT): It starts at the Bowman's capsule. 2. Loop of Henle: U-shaped tubule lies between the proximal & distal convoluted tubules.  It consists of: A. Descending limb→ (the part which is connected to the proximal convoluted tubule)→ it is thin part B. Ascending limb (the part which is connected to the distal convoluted tubule)  Its first part is thin.  Its distal part is thick.  Renal tubule 3. Distal convoluted tubules (DCT):  About 8 DCTs unite to form a cortical collecting duct passes downwards into the medulla, where it becomes a medullary collecting duct.  Medullary collecting duct form larger ducts that drain into  the minor calyces at the tips of renal papillae.  Minor calyces unite to form the major calyces that empty in the renal pelvis.  Glomerulus & Renal tubule Nephrons  An outer cortex All glomeruli located in the cortex So it is Granular An Inner medulla Loops of Henle and collecting ducts in medulla So it is striated  Types of the nephrons according to situation of the renal glomeruli 1- Cortical Juxtamedullary juxtamedullary nephrons Cortical nephrons  Types of the nephrons Cortical nephrons Juxtamedullary nephrons: Location of Inner portions of the renal cortex near to the glomeruli Outer portions of the renal cortex medulla % of total number 85% 15% of the nephrons Penetrate only short distances into the Penetrate deeply into the inner parts of the Loops of Henle outer part of the medulla. medulla. give rise to peritubular capillaries that Give rise to 2 types of capillaries. surround all parts of the nephron 1) Peritubular capillaries that surrounds PCT & DCT in renal cortex. Efferent arterioles 2) Straight capillaries (vasa recta) that accompany the long loop of Henle thought medulla then, return back upwards to drain into the cortical veins. Function Filtration of plasma/ Urine formation Essential for the process of urine concentration The renal circulation Glomerular capillary bed First capillary bed  Second capillary bed Peritubular capillary bed  Glomerular capillary beds Peritubular capillary beds Formed from the afferent arterioles Formed from the efferent arterioles and drains into the efferent arterioles and drains into the interlobular veins A high pressure bed that favors A low pressure bed that favors filtration reabsorption Second capillary bed Peritubular capillary bed  The course of the circulation in cortical and juxtamedullary nephrons (1) In the cortical nephrons, the efferent arterioles break into a network of peri-tubular capillaries that supply the whole tubules. (2) In the juxtamedullary nephrons, the efferent arterioles break into 2 types of capillaries: (a) Peri-tubular capillary network that supplies the PCT & DCT (b) The vasa recta that dip into the medulla alongside the LH.  The Juxtaglomerular apparatus It is a highly specialized functional complex located near the glomerulus of each nephron (juxta = near). It is located between the afferent and efferent arterioles and the returning initial part of distal convoluted tubule of the same nephron. The Juxtaglomerular apparatus  The Juxtaglomerular apparatus formed of 3 components 1- Juxtaglomerular 2-Macula densa 3- Lacis or cells cells mesangial) cells  Juxtaglomerular (JG) cells:  Present in wall of afferent arteriole  Acts as baroreceptors Macula densa cells: Present in initial part of DCT Acts as chemoreceptors Lacis cells: Found in area between juxtaglomerular & macula densa cells Its function is unknown The Juxtaglomerular apparatus Functions of The Juxtaglomerular apparatus 1) Endocrine (Juxtaglomerular cells): It secrete renin that regulates arterial Blood Pressure. 2) Paracrine (Macula densa cells): It secretes prostaglandins and adenosine that have an important role in autoregulation local renal blood flow and glomerular filtration.  Stimulants for renin secretion 1. Fall in arterial blood pressure 2. Reduction in the ECF volume 3. Decreased load of sodium and chloride in macula densa 4. Increased sympathetic activity The Juxtaglomerular apparatus Overview of Kidney Functions  1- Water balance 2- Ion (electrolyte) balance A) Regulatory functions 3- Acid-base balance 4- Arterial blood pressure regulation 5- Maintenance of ECF osmolarity  1- Excreting endogenous waste products as urea, creatinine B) Excretory function 2- Excreting exogenous waste products as drugs & food additives  C) Endocrinal functions, it secretes 1- 3- Actives vitamin 2- Renin Erythropoietin D  3- Endocrinal function 1-Erythropoietin: it controls erythrocyte production 2-Renin:  It an enzyme that controls formation of angiotensin, which influences blood pressure and sodium balance 3- Conversion of 25-hydroxyvitamin D to 1,25- dihydroxyvitamin D, which influences calcium balance Erythropoietin Vitamin D