Chapter 2 - Chapter 2 Structure and Function of the Kidneys...

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Chapter 2 Structure and Function of the Kidneys and the Lower Urinary Tract Structure of the Kidneys Structure and function of the kidneys are closely linked. Gross Anatomy Paired, retroperitoneal (lie on the posterior wall of the abdomen, behind the peritoneum on either side of the vertebral column, under the ribs). Weight: 115 – 170 g 11 x 6 x 3 cm (L) (W) (Thick) Cortex and medulla and papilla (outer) (inner) (inner most tip of inner medulla) - Composed of nephrons, blood vessels, lymphatics, and nerves. - Medulla divided into 8 – 12 conical masses called renal pyramids. - See fig. 2-1, p.18(Koeppen) Renal Vasculature Blood flow to the kidneys = 25% of cardiac output (1.25 L/min) Kidneys constitute < 0.5 % of TBW Renal artery branches progressively to form the interlobar artery. Interlobar artery gives rise to arcuate artery. Arcuate to interlobular artery Interlobular to afferent arteriole Afferent arterioles to glomerular capillaries (glomerulus) Glomerular capillaries to efferent arteriole. Efferent arterioles lead into a capillary network, peritubular capillaries (around nephrons) Peritubular capillaries supply blood to the nephron. - Juxtamedullary nephron’s peritubular capillaries also give rise to the vasa recta* - Blood from ascending recti enters the arcuate vein, interlobar vein, and renal vein, which courses beside the ureter. * Note: specialization long, hairpin – shaped vessels follow the course of the loop of Henle serves as osmotic exhangers for producing concentrated urine
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Ultrastructure of the Nephron The functional unit of the kidney is the nephron. Each kidney contains ~ 1.2M nephrons The nephron consists of a: A. Renal corpuscle (glomerulus) B. Renal tubule A. Glomerulus Consists of glomerular capillaries and Bowman’s capsule (cup- like, proximal end of tubule) Glomerular capillaries are capillary tufts from efferent arterioles, inside Bowman’s capsule. Blood is ultrafiltered* across glomerular capillaries into Bowman’s capsule. - This is the first step in urine formation. Ultrastructure of the Nephron Corpuscle 1. The glomerular capillaries are covered by epithelial cells, called podocytes , which are endocytic. 2. The capillary endothelium, basement membrane, and foot processes of podocytes form filtration barrier. - The endothelium is fenestrated, allowing water, Na+, urea, glucose and even small proteins. - The basement membrane is a porous matrix of extracellular proteins, such as type IV collagen, laminin, fibronectin, and other negatively charged proteins. - The processes of the podocytes interdigitate to cover the basement membrane and are separated by gaps, called filtration slits . -
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This note was uploaded on 01/07/2012 for the course PHCH 6234 taught by Professor Farqui during the Winter '11 term at Palmer Chiropractic.

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Chapter 2 - Chapter 2 Structure and Function of the Kidneys...

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