Y khoa, dược - The urinary system

26The Urinary System26-2Learning Outcomes26.1 Describe the structure, location, and functions of the kidney.26.2 Define the term nephron and describe its structure.26.3 Explain how nephrons filter blood and form urine.26.4 List substances normally found in urine.26-3Learning Outcomes (cont.)26.5 Describe the locations, structures, and functions of the ureters, bladder, and urethra.26.6 Explain how urination is controlled.26.7 Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.26-4IntroductionSystem functions to remove waste products from the bloodMain functional units of the kidneys are the nephronsNephrons filter the blood and form the urineUrinary System OrgansKidneysUretersBladderUrethra26-5The KidneysFunctions Remove metabolic waste products from the blood Secrete the hormone erythropoietin, which stimulates  bone marrow to produce red blood cells Secrete the hormone renin, which helps regulate blood pressureDescriptionThe kidneys are bean-shaped organs that lie behind the peritoneal cavity (retroperitoneal) on either side of the vertebral column.26-6The Kidneys (cont.)Renal sinus – concave depression of the surface of the kidneyHilum – point of entry for the renal artery, renal vein, and ureterRenal pelvis – expansion of the ureter that further divides into calycesKidney26-7The Kidneys (cont.)Renal cortex – outermost portion of the kidney that covers the pyramids and dips down between themRenal medulla – middle portion that also divides into renal pyramidsRenal column – portion of the cortex between pyramidsKidney26-8Previous26-9NephronsRemoves waste products from the bloodEach kidney contains about 1 million nephronsMade of a renal corpuscle and a renal tubuleRenal Corpuscles Composed of a group of capillaries  called a glomerulus Glomerulus is surrounded by  Bowman’s capsule Blood filtration occurs in corpuscle Extend from the Bowman’s capsule of a nephron Consist of three parts: Proximal convoluted tubule Loop of Henle Distal convoluted tubuleRenal TubulesGlomerulus 26-10Previous26-11Nephrons (cont.)Blood Flow Through NephronVeins of the KidneyAfferent ArterioleGlomerulusEfferent ArteriolePeritubular Capillaries Afferent arterioles deliver blood to the glomeruli Efferent arterioles carry blood from the glomeruli to peritubular capillaries26-12Apply Your KnowledgeWhat are the functions of the kidney?ANSWER: The kidney removes metabolic waste products from the blood, secretes erythropoietin to help regulate RBC production, and secretes renin to help regulate the BP.Correct!26-13Urine FormationGlomerular FiltrationFirst process occurs in renal corpusclesFluid part of the blood is forced from glomerulus into Bowman’s capsuleBecomes glomerular filtrate Glomerulus 26-14Urine Formation (cont.)Factors affecting glomerular filtrationFiltration pressure – amount of pressure that forces filtrate from the glomerulus into Bowman’s capsuleDetermined by blood pressureRate of filtration – sympathetic nervous system controlConstriction of afferent arterioles decreases filtration pressure26-15Tubular ReabsorptionSecond process in urine formationGlomerular filtrate  proximal convoluted tubuleNutrients, water, and ions pass through the walls of the renal tubule into the peritubular capillariesWater reabsorption depends on hormonesAntidiuretic hormone (ADH)AldosteroneBoth increase water reabsorption, which decreases urine productionTubular Reabsorption26-16Tubular Secretion Third process of urine formationSubstances move from blood in the peritubular capillaries into the renal tubulesSecreted substancesDrugsHydrogen ionsWaste productsTubular Secretion26-17Tubular ReabsorptionTubular SecretionPrevious26-18Urine Formation (cont.)Urine compositionMostly waterUrea and uric acidFormed by the breakdown of proteins and nucleic acidsTrace amounts of amino acids and various ionsSecretion of waste products helps maintain the acid-base balance26-19Apply Your KnowledgeMatch the following:___ Second process in urine formation A. Glomerular filtration___ Substances move from blood into renal tubules B. Tubular reabsorption___ Depends on filtration pressure C. Tubular secretion___ Third process of urine formation___ First process of urine formation___ Filtrate flows into the proximal convoluted tubuleCCBAABANSWER:Nice Job!26-20UretersLong muscular tubes Carry urine to the bladderPeristalsis – rhythmic muscular contraction of uretersUreters26-21Urinary BladderExpandable muscular organ Stores up to 600 ml urine on averageDetrusor muscle – smooth muscle in wall of bladderTrigone – triangle on internal floor of bladder formed by urethra and uretersMicturationProcess of urinationStretching of bladder triggers processApproximately 150cc of urineBladder26-22Previous26-23Impulses to contract urethra; inhibit micturition impulse until ready to urinateUrinationExternal urethral sphincter relaxesMicturition reflex – impulses from pons and hypothalamusDetrusor muscle contractsUrine expelledBladderdistendsStretch receptorsSpinal cordParasympathetic nerves stimulate detrusor muscleBrain stemandcerebralcortex26-24UrethraTube that moves urine from the bladder to the outside worldShorter in females – patient educationUrinate when urge occursDrink adequate clear fluidsWipe front to backUrinate after intercourseUrethra26-25True or False:___ Ureters move urine by peristalsis.___ The detrusor is formed by the openings of the ureters and urethra.___ The process of micturition is triggered when the bladder contains about 150 ml urine.___ The urethra move urine from the kidney to the bladder.___ The urethra is longer in females.___ Contraction of the detrusor muscle pushes urine from the bladder.Apply Your KnowledgeFFTFTtrigonemalesuretersTANSWER:Impressive!26-26Diseases and Disorders of the Urinary SystemDisease/DisorderDescriptionAcute renal failureSudden loss of kidney function; may be reversible with treatmentChronic renal failureKidneys slowly lose ability to function; not reversibleCystitisUrinary bladder infection; more common in femalesGlomerulonephritisInflammation of the glomeruli of the kidney; one cause of chronic renal failureIncontinenceInability to control urination26-27Diseases and Disorders of the Urinary SystemDisease/DisorderDescriptionPolycystic kidney diseaseEnlargement of kidneys because of the presence of many cysts within them; slow, progressive diseasePyelonephritisComplicated urinary tract infection; starts with a bladder infection and spreads to both kidneys; can be acute or chronicRenal calculiKidney stones; can become lodged in ducts within kidneys or ureters26-28Apply Your KnowledgeMatching:___ Complicated urinary tract infection A. Pyelonephritis___ Inability to control urination B. Glomerulonephritis___ Kidney stones C. Incontinence___ Slow loss of kidney function D. Chronic renal failure___ Bladder infection E. Renal calculi___ Inflammation of the glomeruli F. Cystitis___ Kidney enlargement due to cysts G. Acute renal failure___ Sudden loss of kidney function H. Polycystic kidney diseaseHGFEDCBAANSWER:GOOD JOB!26-29In Summary26.1 The retroperitoneal kidneys are composed of the outer renal cortex and inner renal medulla. Their function is to remove metabolic waste from the body.26.2 A nephron is a single kidney cell. It is composed of a renal corpuscle containing the glomerulus and Bowman’s capsule and the three sections of the renal tubule: proximal convoluted tubule, loop of Henle, and distal convoluted tubule. 26-30In Summary (cont.)26.3 The nephrons filter blood and form urine through three processes: glomerular filtration, tubular reabsorption, and tubular secretion.26.4 Some of the components of urine include water, urea, uric acid, trace amounts of amino acids, and various ions.26.5 The two ureters are long tubes extending from each renal pelvis that bring urine to the bladder for storage. The urethra is the muscular tube extending from the bladder that allows urine to be expelled from the body.26-31In Summary (cont.)26.6 Urination is controlled by a variety of factors including bladder distention, parasympathetic nerve stimulation, brain impulses affecting urethral sphincters, and contractions of the detrusor muscles of the bladder.26.7 The diseases and disorders of the urinary system include infections of the bladder and kidneys, bladder control, and the different types of renal (kidney) failure and disease. These are discussed in more detail in the Pathophysiology section of this chapter. 26-32End of Chapter 26This too shall pass—just like a kidney stone.~H. Madson