Describe the structures of the urinary system and explain their function.Kidneys:Organs that produce urineUrinary Tract:Organs that eliminate urineUreters: Paired tubesUrinary Bladder: Muscular sacUrethra: Exit tubeExplain the function of the urinary systemThree Functions of the Urinary System:1. Excretion2. EliminationUrination or MicturitionThe process of eliminating urineContraction of muscular urinary bladder forces urine through urethra, and out of body3. Homeostatic Regulation of Blood Plasma Volume and Solute ConcentrationExplain how the urinary system maintains homeostasis within the body1. Regulates Blood Volume and Blood PressureBy adjusting volume of water lost in urineReleasing erythropoietin and renin2. Regulates Plasma Ion ConcentrationsSodium, potassium, and chloride ions (by controlling quantities lost in urine)Calcium ion levels (through synthesis of calcitriol)3. Helps Stabilize Blood pHBy controlling loss of hydrogen ions and bicarbonate ions in urine4. Conserves Valuable NutrientsBy preventing excretion while excreting organic waste products5. Assists LiverIn detoxifying poisonsAlso during starvation, deaminates amino acids so other tissues can metabolize them for energyDescribe the anatomy of the kidneyLocated on either side of vertebral columnLeft kidney lies superior to right kidneySuperior surface capped by adrenal glandPosition Maintained By:Overlying peritoneumContact with adjacent visceral organsSupporting connective tissuesFloating Kidney:Suspensory fibers damaged, kidney displaced, can cause pain, distortion, or ureter/blood vessels during movementEach Kidney is Protected and Stabilized by Three Concentric Layers of Connective Tissue:1. Fibrous Capsule (innermost layer)A layer of collagen fibersCovers outer surface of entire organ2. Perinephric Fat CapsuleA thick layer of adipose tissue3. Renal Fascia (outermost layer)A dense, fibrous outer layerAnchors kidney to surrounding structuresTypical Adult Kidney:10 cm. long, 50.5 cm. wide, 3 cm thick (4 in. x 2.2 in. x 1.2 in.)Weighs about 150 g (5.25 oz)Hilum:Point of ENTRY for renal artery and renal nervesPoint of EXIT for renal vein and ureterRenal Cortex:Superficial portion of kidney in contact with renal capsuleReddish brown and granularRenal Pyramids:6-18 distinct conical or triangular structures in renal medullaBase abuts cortexTip (renal papilla) projects into renal sinusRenal Columns:Bands of cortical tissue separate adjacent renal pyramidsExtend into medullaHave distinct granular textureRenal Lobe:Consists Of:Renal PyramidOverlying area of renal cortexAdjacent tissues of renal columnsProduces UrineRenal Papilla:Ducts discharge urine into Minor calyx, a cup-shaped drainMajor Calyx:Formed by 4 or 5 minor calycesRenal Pelvis:Large, funnel-shaped chamberConsists of 2 or 3 major calycesFills most of renal sinusConnected to ureter, which drains kidneyDescribe the blood supply to the kidneysKidneys receive 20%–25% of total cardiac output1200 mL of blood flows through kidneys each minuteKidney receives blood through renal arteryBlood flow:From renal artery → segmental arteries → interlobar arteries → arcuate arteries → cortical radiate (interlobular) arteries → afferent arterioles → glomerulus efferent arteriole → peritubular capillaries → venules → cortical radiate (interlobular) veins → arcuate veins → interlobar veins → renal veinExplain the function of the renal nervesRenal Nerves:Innervate kidneys and uretersEnter each kidney at hilumFollow tributaries of renal arteries to individual nephronsSympathetic InnervationAdjusts rate of urine formation by changing blood flow and blood pressure at nephronStimulates release of reninRestricts losses of water and salt in urine by stimulating reabsorption at nephron (renin-angiotensin system stimulates aldosterone release from adrenal cortex)Describe the structure of the nephron and explain its functionNephron: functional unit of the kidneyMicroscopic, tubular structures in cortex of each renal lobeEach kidney has approximately 1.25 million nephronsWhere urine production beginsConsists of:1. Renal tubule2. Renal corpuscleOrganization of the Nephron:Traveling along tubule, filtrate (tubular fluid) gradually changes compositionDue to reabsorption and secretion of substancesChanges vary with activities in each segment of nephronEach Nephron empties into the collecting systemWhat is found in the renal corpuscle?Renal Corpuscle:Spherical structureEach renal corpuscle is 150-250 µm in diameterConsists Of:1. Glomerular Capsule (Bowman’s Capsule)Forms outer wall of renal corpuscleEncapsulates glomerular capillaries2. Cup-shaped chamber3. Capillary network (glomerulus)Knot of fenestrated capillariesCapillaries are “enveloped” by podocytesPodocytes: cells that have complex processes or “feet” (pedicles) that wrap around the capillariesFiltration Slits: narrow gaps between pediclesAllows small substances to pass out of capillaryExplain the difference between the renal tubule and the glomerulusRenal Tubule:Lone tubular passagewayBegins at renal corpuscleFunctions:1. Reabsorb useful organic nutrients that enter filtrate2. Reabsorb more than 90% of water in filtrate3. Secrete waste products that failed to enter renal corpuscle through filtration at glomerulusSegments of Renal Tubule:Located in cortex1. Proximal Convoluted Tube (PCT)2. Nephron Loop (Loop of Henle)U-shaped tubeExtends partially into medullaIn juxtamedullary nephrons, loop extends deeper into the medulla (important for their function!)3. Distal Convoluted Tubule (DCT)Glomerulus:Consists of 50 intertwining capillariesBlood delivered via afferent arterioleBlood leaves in efferent arterioleFlows into peritubular capillaries which drain into small venules and return blood to venous systemNote: Blood leaves the capillary network through the efferent arteriole and NOT through a venuleDifferences:Explain where filtration, reabsorption, and secretion takes place on the nephron. What is filtered, reabsorbed, and/or secreted?Filtration:Occurs in renal corpuscleBlood Pressure:1. Forces water and dissolved solutes out of glomerular capillaries into capsular space2. Produces protein-free solution (filtrate), similar to blood plasma except lacks proteinsFiltration membrane prevents large molecules from passing throughBlood Pressure forces water and small solutes across membrane into capsular spaceLarger solutes, such as plasma proteins, are excludedNot filtered out of plasma so not found
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