renal system lec.1.pdf

Renal system By Assist. Prof. Dr. Zainab H.H AlAmily Lec.1  Objectives 1. List the functions of kidney 2. Describe the morphology of the typical nephron and its blood supply. 3. Describe the concept of clearance  The Role of the Kidneys...

Renal system By Assist. Prof. Dr. Zainab H.H AlAmily Lec.1  Objectives 1. List the functions of kidney 2. Describe the morphology of the typical nephron and its blood supply. 3. Describe the concept of clearance  The Role of the Kidneys in the Body Includes: 1. Regulation of the volume and composition of the ECF, by maintaining a balance between intake and output of water and electrolytes in the body. 2. Excretion and elimination of waste products of metabolism, such as the excretion of urea, creatinine and uric acids; as well as the excretion of various toxins such as drugs and food additives. 3. The kidneys act as endocrine glands producing hormones, such as “erythropoietin hormone” and renin.  4. Playing a dominant role in the long-term and short-term regulation of arterial blood pressure. F 5. Kidneys along with the respiratory system contribute to acid-base O regulation. O T E 6. Finally, kidneys synthesize glucose from amino acids and other R precursors  What is excretion?
Throwing out of waste product is known as excretion. The organs through which excretion occurs. F 1. Kidneys: Excrete water and water soluble waste products. O 2. Lungs: Excrete carbon dioxide, water vapour and other volatile O T substances such as acetone. E 3. Skin: Excretes water and salts mainly in the form of sweat. R 4. Gastrointestinal tract: Excretes undigested food.  Metabolic waste products excreted by kidneys are:
1. Urea from protein. 2. Uric acid from nucleic acid. 3. Creatinine from muscle creatine. F O 4. End products of haemoglobin breakdown O T E R  STRUCTURE OF NEPHRON Nephron is a structural and functional unit of the kidney. Each nephron is capable of forming urine. There are two types of nephrons: F O 1. Cortical nephrons. Glomeruli are present near the surface of the O kidneys. T These nephrons constitute about 86% of total nephrons. E R The main function of cortical nephrons is absorption of sodium. 2. Juxtamedullary nephrons. Glomeruli lie at the junction of cortex and medulla of the kidney. These constitute 14% of the nephrons. The main role of juxtamedullary nephron is to increase concentration of medullary interstitial fluid.  Two kidneys together have two millions nephrons. Nephron consists of two major parts: Glomerulus. F A long renal tubule. O O 1. Glomerulus. It is made up of tuft of capillaries which connect T afferent arteriole with an efferent arteriole. E R Capillaries have single layer of endothelial cells attached to a basement membrane.  Bowman’s capsule encloses the glomerulus and is formed of two layers: inner layer which covers the glomerular capillaries is called visceral layer, F outer layer is called parietal layer. O  Space between visceral and parietal layers is continued as the lumen of the O tubular portion. T E fluid-filled space, Bowman’s space, is formed within the capsule. R Blood of capillary and fluid of Bowman’s space are separated by the glomerular membrane. From the Bowman’s capsule, tubule of the nephron extends, the lumen of which is continuous with the Bowman’s space.  2. Renal tubule. It is mainly formed of three parts: (a) Proximal convoluted tubule. F (b) Loop of Henle consisting of: O Thin segment :walls of descending limb and lower end of ascending limb are O very thin. Therefore, they are termed thin segment. T Hair pin bend. E Thick ascending limb or segment R  BLOOD FLOW TO KIDNEYS Rate of blood flow to kidneys is 1200 ml/min. This is quite high as compared to their size. F State peculiarities of renal circulation. O 1.Very high blood supply, about 21% of cardiac output. O 2.Two sets of capillaries. T The glomerular capillaries. E These combine to form efferent arteriole which in turn breaks into peritubular R capillary network around the tubules of cortical nephrons.  vasa recta which are loop-shaped vessels in juxtamedullary nephrons the efferent arterioles continue as these loops dip into the medullary pyramids alongside the loops of Henle F O 3.Glomerular capillary bed has a high hydrostatic pressure O T because efferent arteriole is of a smaller diameter than E afferent arteriole which offers considerable resistance to R blood flow.  4. Peritubular capillary bed is a low pressure bed. 5. Only 1 to 2% of blood flows through vasa recta. The flow is very sluggish. F O 6. Renal blood flow shows remarkable constancy in face of blood O pressure changes due to autoregulation T E R  The kidneys regulate the hydrostatic pressure in both capillary beds (glomerular & peitubular ) , by adjusting resistance of the afferent and efferent arterioles. F O High hydrostatic pressure in GC (60 mmHg) causes rapid fluid O filtration; whereas a much lower pressure in the peritubular T capillaries (13 mmHg) permits rapid fluid reabsorption E R The afferent arteriole is a short, straight branch of the interlobular artery. The efferent arteriole, that drains the GC, has a relatively high resistance than the afferent arteriole. THANK YOU  (c) Distal convoluted tubules. open into initial arched collecting ducts called cortical collecting ducts present in renal cortex. F Seven to ten such ducts form straight collecting duct which passes into O medulla forming medullary collecting ducts. O T In the inner zone of medulla they form papillary ducts or ducts of E Bellini. R These open into papilla of minor calyces. Three or four minor calyces unite to form one major calyx. The major calyces open into pelvis of ureter. The pelvis is an expanded portion present in renal sinus and it continues as ureter