CHAPTER 26 - CHAPTER 26 UR I NARY SYSTEM The kidneys do the...

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Unformatted text preview: CHAPTER 26 UR I NARY SYSTEM The kidneys do the major work of the urinary system. Other parts are mainly passageways and storage areas. Parts: 2 kidneys 2 ureters 1 urinary bladder 1 urethra Nephrology and urology are terms for the branch of medicine concerned with the urinary system. Functions of the kidneys: Regulation of ion levels in blood Regulation of blood pH Regulation of blood volume Regulation of blood pressure Maintaining blood osmolarity (proper ratio of water to solutes) Release of hormones Calcitriol—active form of Vit. D Erythropoietin—increased production of RBC Regulation of blood glucose level—kidney cells can produce glucose and release it into the blood when needed. Excretion of wastes and foreign substances K I DNEYS Paired reddish kidney-bean shaped organs, located retroperitoneal, just above the waist with the right kidney slightly lower than the left. On the average, about 4-5" long and 2-3" wide with a medial concave border, the hilus, where the ureter, blood vessels, lymphatics, and nerves enter and leave. Each kidney is surrounded by 3 layers: Renal capsule (inner layer)—smooth transparent fibrous membrane—barrier against trauma and spread of infection \ Adipose capsule—mass of fatty tissue for protection Renal fascia (outer layer)—thin layer of dense irregular CT that anchors kidney in place A section through the kidney shows an outer reddish cortex and an inner, reddish-brown medulla. Within the medulla are 8-18 cone-shaped renal pyramids. Their bases face the cortex and the apexes, called renal papillae, face the hilus. Portions of the cortex called renal columns extend between the pyramids, inside the kidney is a large cavity, the renal pelvis, which becomes continuous medially with the ureter. The lateral edge of the pelvis contains cuplike extensions called major and minor calyces, which bring urine in to the pelvis. Kidneys receive through the renal arteries 20-25% of resting cardiac output. As the renal artery enters each kidney, it gives off 5 segmental arteries, which continue to branch and eventually form the afferent arterioles to the glomeruli. Efferent arterioles emerge from the glomeruli. Afferents are larger than efferents, which is what creates the pressure to force fluids across the filtration membrane. After leaving the glomerulus, the efferent arteriole forms a network of peritubular capillaries around the PCT and the DCT and also another capillary network the vasa recta, which surrounds the loops of Henle of juxtaglomerular nephrons. Blood leaves the kidney through the renal vein. Nerve supply to the kidneys is from the renal plexus-these are sympathetic vasomotor nerves which regulate the diameter of arterioles with the kidney. Most of the control of activities in the kidney is hormonal. The nephron is the functional unit of the kidney. 3 basic functions: Filtration Reabsorption Secretion These processes together result in urine formation....
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This note was uploaded on 07/26/2011 for the course BSC 1094 taught by Professor Porter during the Fall '11 term at Edison State College.

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CHAPTER 26 - CHAPTER 26 UR I NARY SYSTEM The kidneys do the...

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