Chapter 25

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  • Topic: Kidney, Nephron, Kidney anatomy
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  • Published : February 7, 2012
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Chapter 25:
Urinary System: Anatomy Review
1. The human kidney is composed of three distinct regions; the renal cortex, medulla, and pelvis. 2. The nephron is the structural and functional unit of the kidneys. There are two types; cortical nephrons (lie largely in cortex) and juxtamedullary nephrons (lie in cortex and medulla) 3. The diameter of the efferent arteriole is smaller than that of the afferent arteriole. 4. In the nephron, fluid enters glomerular ( Bowman’s) capsule, to proximal convoluted tubule, to the descending loop of henle, to ascending loop of henle, to the distal convoluted tubule, to cortical collecting duct, to medullary collecting duct 5. The juxtaglomerular apparatus is composed of macula densa and granular cells. Urinary System: Glomerular Filtration

1. The formation of urine by the kidney involves three main processes; filtration, reabsorption, and secretion. 2. The fluid collecting in the capsular space is called glomerular filtrate. 3. Glomerular hydrostatic pressure drives filtration.

4. Net filtration is the sum of all hydrostatic and osmotic pressures acting at a filtration membrane. 5. The regulatory mechanism of renal processes are; myogenic mechanism, tubuloglomerular mechanism, and sympathetic control. Urinary System: Early Filtrate Processing

1. To be reabsorbed by the blood, substances in the filtrate must cross the barrier formed by the tubular cells. 2. Transcellular pathway involves crossing the luminal and basolateral membranes. 3. Paracellular pathway involves crossing through the tight junctions. 4. Na+ K+ ATPase ion pumps drive the reabsorption of water and solutes by increasing the sodium ion concentration of the interstitium. 5. Hydrogen ions are secreted into the filtrate to maintain an acid/base balance. Urinary System: Late Filtrate Processing

1. The cortical collecting duct is composed of principal cells and intercalated cells. 2. Principal cells are permeable to sodium ions only in the presence of...
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