Anatomy Of Kidney

KIDNEY ANATOMY The kidneys lie on the posterior wall of the abdomen, one on each side of the vertebral column. The right kidney is placed slightly lower then the left. Each kidney is surrounded by a layer of fibrous capsule.

Below the capsule and between the pyramids is present a layer of reddish brown tissue which is called as cortex. The innermost layer which consists of the conical shaped pyramids is called as medulla. The concave medial border of the kidney where renal blood, lymph vessels and nerves enter is called as hilum.

The funnel shaped structure which behaves as a receptacle for urine formed by the kidneys is called as the renal pelvis. The pelvis has a number of branches called calyces. The urine formed by the kidney passes into lesser calyx, from this it passes into greater calyx and then through the pelvis into the ureter.

STUCTURE The kidney is composed of large number of small units called as nephrons, which are structurally and functionally similar. The nephron is made up of vascular component, glomerulus and a tubular component. The first part of the tubular component is Bowman's capsule. This is lined by single layer of epithelial cells. Bowman's capsule is associated with glomerulus which enters into the Bowman's capsule and is covered completely by the epithelial lining.

The afferent and efferent arterioles are also present in the Bowman's capsule. The afferent arterioles carries blood into the nephron and efferent arterioles carries blood from the nephron. The Bowman's capsule leads to the next portion of the tubule called as Proximal convoluted tubule and the next part of the tubule is thin and is called as loop of henle . It has two limbs, the ascending limb and the descending limb. After this the tubule again becomes convoluted and this npart is called as Distal convoluted tubule. The last part of the nephron comprises of the collecting ducts.

FUNCTIONS 1. The kidneys help in the removal of the metabolic waste products from the blood. 2. The kidneys help in maintaining the constant composition of the blood. 3. The kidneys help in the regulation of acid base balance 4. Kidneys regulate the excretion of the salts from the body. 5. The kidneys also regulate the excretion of water from the body. 6. They also play a vital role in the maintenance of the blood pressure.

Tips to Remember PCT brush border present carbonia anhydrase present leaky- tight junctions

CORTICAL NEPHRON FORMS 85% OF NEPHRONS SHORT LOOP OF HENLE. Blood flow large. pO2 – 50mmHg

DCT absent tight- tight junctions

JUXTAMEDULLARY NEPHRON 15% Lonf loop of henle. Less blood flow. 15mmHg.

IMPORTANT POINTS TO REMEMBER 1. Special cells in collecting tubule P- PRINCIPAL CELLS – FOR Na reabsorbtion. I- INTERCALATED CELL - FOR acid secretion.

MESANGIAL CELLS: 1. glomerular mesangial cells- contractile nature, important role in regulation of glomerular filtration. 2. extraglomerular mesangial cells.- part of juxtaglomerular apparatus.

JUXTAGLOMERULAR APPARATUS: 1. Juxtaglomerular cells contain rennin containing granules. 2. Macula densa cells. 3. Lacis cells.

RENAL TUBULAR SECRETION Transport of solutes from peritubular capillaries into tubular lumen.

RENAL TUBULAR REABSORPTION Transport of solutes from tubular lumen to peritubular capillaries.