introduction of Kidney & kidney anatomy There are 2 kidneys , they are bean shaped and reddish brown. - They are located between the peritoneum and the posterior wall of the abdomen. Cortex: superficial layer. Medulla : Inner portion , arranged in pyramids , there are 8 – 18 pyramids per kidney separated by renal columns. The apex of each pyramid extends toward the renal pelvis and forms a papilla which projects into minor calyces → major calyces, which in turn unite to form renal pelvis. The nephron : the functional unit of the kidney There are approximately one million nephrons in each kidney. The number of nephrons is constant from birth. It consists of : 1. Renal corpuscle : Bowman's capsule & the glomerulus within it : It is the site of filtration of the blood. 2. Proximal convoluted tubule. 3. Loop of henle. 4. Distal convoluted tubule. 5. Collecting duct : drains into the renal pelvis. Renal blood flow : - The kidneys get 20 - 25 % of cardiac output. - Renal artery divides to form interlobar arteries ( that run between the medullary pyramids ) → arcuate arteries (run in the corticomedullary junction) → interlobular arterioles ( run in the cortex ) → Afferent arterioles → Glomeruli → Efferent arterioles which divide into the vasa recta and the peritubular capillaries , this is a network of capillaries which allows movement of fluids and solutes out of the tubules. Functions : Regulation of water & electrolyte balance. Regulation of acid base balance. Excretion of water soluble waste : urea , uric acid , creatinine , drugs ...... Endocrine : Renin – angiotensin system , erythropoietin , vitamin D activation. Glomerular filtration rate : It is the volume of fluid filtered from the renal glomerular capillaries into Bowman’s capsule per minute. In an average man : GFR = 125 ml/min. In women : 10% less than those of men. Clinically , GFR is often measured to determine the renal function. Although the GFR is about 180 L / day , our urine output is only 1-2 L/day ( which is good or else we’d spend the day in the bathroom ) Investigation Of Renal Diseases Aim a) To prove the condition. b) To asses the severity. c) Investigation for the cause. 1- Urine investigations : o Urinalysis : physical , chemical , microscopic ( details : see later ) Urine culture & sensitivity : for UTI 2- Blood investigations : K : 3.5 - 5 mEq/L o CBC. Na , K , Ca , P . o Urea , Creatinine , PH