CHAPTER © 2011 The McGraw-Hill Companies, Inc. All rights reserved. 26 The Urinary System

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Learning Outcomes 26.1Describe the structure, location, and functions of the kidney. 26.2Define the term nephron and describe its structure. 26.3Explain how nephrons filter blood and form urine. 26.4List substances normally found in urine.

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Learning Outcomes (cont.) 26.5Describe the locations, structures, and functions of the ureters, bladder, and urethra. 26.6Explain how urination is controlled. 26.7Describe the causes, signs and symptoms, and treatments of various diseases and disorders of the urinary system.

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Introduction System functions to remove waste products from the blood Main functional units of the kidneys are the nephrons Nephrons filter the blood and form the urine Kidneys Ureters Bladder Urethra

© 2011 The McGraw-Hill Companies, Inc. All rights reserved The Kidneys Functions 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 pressure Description The kidneys are bean-shaped organs that lie behind the peritoneal cavity (retroperitoneal) on either side of the vertebral column.

© 2011 The McGraw-Hill Companies, Inc. All rights reserved The Kidneys (cont.) Renal sinus – concave depression of the surface of the kidney Hilum – point of entry for the renal artery, renal vein, and ureter Renal pelvis – expansion of the ureter that further divides into calyces Kidney

© 2011 The McGraw-Hill Companies, Inc. All rights reserved The Kidneys (cont.) Renal cortex – outermost portion of the kidney that covers the pyramids and dips down between them Renal medulla – middle portion that also divides into renal pyramids Renal column – portion of the cortex between pyramids Kidney

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© 2011 The McGraw-Hill Companies, Inc. All rights reserved Nephrons Removes waste products from the blood Each kidney contains about 1 million nephrons Made of a renal corpuscle and a renal tubule Renal 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 tubule Renal Tubules Glomerulus

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© 2011 The McGraw-Hill Companies, Inc. All rights reserved Nephrons (cont.) Veins of the Kidney Afferent Arteriole Glomerulus Efferent Arteriole Peritubular Capillaries  Afferent arterioles deliver blood to the glomeruli  Efferent arterioles carry blood from the glomeruli to peritubular capillaries

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Apply Your Knowledge What 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!

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Urine Formation Glomerular Filtration –First process occurs in renal corpuscles –Fluid part of the blood is forced from glomerulus into Bowman’s capsule Becomes glomerular filtrate Glomerulus

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Urine Formation (cont.) Factors affecting glomerular filtration –Filtration pressure – amount of pressure that forces filtrate from the glomerulus into Bowman’s capsule Determined by blood pressure –Rate of filtration – sympathetic nervous system control Constriction of afferent arterioles decreases filtration pressure

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Tubular Reabsorption Second process in urine formation Glomerular filtrate  proximal convoluted tubule –Nutrients, water, and ions pass through the walls of the renal tubule into the peritubular capillaries Water reabsorption depends on hormones –Antidiuretic hormone (ADH) –Aldosterone –Both increase water reabsorption, which decreases urine production Tubular Reabsorption

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Tubular Secretion Third process of urine formation Substances move from blood in the peritubular capillaries into the renal tubules Secreted substances –Drugs –Hydrogen ions –Waste products Tubular Secretion

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Tubular ReabsorptionTubular Secretion Previous

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Urine Formation (cont.) Urine composition –Mostly water –Urea and uric acid Formed by the breakdown of proteins and nucleic acids –Trace amounts of amino acids and various ions Secretion of waste products helps maintain the acid-base balance

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Apply Your Knowledge Match 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 tubule C C B A A B ANSWER: Nice Job!

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Ureters Long muscular tubes Carry urine to the bladder –Peristalsis – rhythmic muscular contraction of ureters Ureters

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Urinary Bladder Expandable muscular organ –Stores up to 600 ml urine on average Detrusor muscle – smooth muscle in wall of bladder Trigone – triangle on internal floor of bladder formed by urethra and ureters Micturation –Process of urination –Stretching of bladder triggers process Approximately 150cc of urine Bladder

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© 2011 The McGraw-Hill Companies, Inc. All rights reserved Impulses to contract urethra; inhibit micturition impulse until ready to urinate Urination –External urethral sphincter relaxes –Micturition reflex – impulses from pons and hypothalamus –Detrusor muscle contracts –Urine expelled Bladder distends Stretch receptors Spinal cord Parasympathetic nerves stimulate detrusor muscle Brain stem and cerebral cortex

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Urethra Tube that moves urine from the bladder to the outside world Shorter in females – patient education –Urinate when urge occurs –Drink adequate clear fluids –Wipe front to back –Urinate after intercourse Urethra

© 2011 The McGraw-Hill Companies, Inc. All rights reserved True 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 Knowledge F F T F T trigone males ureters T ANSWER:

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Diseases and Disorders of the Urinary System Disease/DisorderDescription Acute renal failureSudden loss of kidney function; may be reversible with treatment Chronic renal failureKidneys slowly lose ability to function; not reversible CystitisUrinary bladder infection; more common in females GlomerulonephritisInflammation of the glomeruli of the kidney; one cause of chronic renal failure IncontinenceInability to control urination

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Diseases and Disorders of the Urinary System Disease/DisorderDescription Polycystic kidney disease Enlargement of kidneys because of the presence of many cysts within them; slow, progressive disease PyelonephritisComplicated urinary tract infection; starts with a bladder infection and spreads to both kidneys; can be acute or chronic Renal calculiKidney stones; can become lodged in ducts within kidneys or ureters

© 2011 The McGraw-Hill Companies, Inc. All rights reserved Apply Your Knowledge Matching: ___ Complicated urinary tract infectionA. Pyelonephritis ___ Inability to control urinationB. Glomerulonephritis ___ Kidney stonesC. Incontinence ___ Slow loss of kidney functionD. Chronic renal failure ___ Bladder infectionE. Renal calculi ___ Inflammation of the glomeruliF. Cystitis ___ Kidney enlargement due to cystsG. Acute renal failure ___ Sudden loss of kidney functionH. Polycystic kidney disease H G F E D C B A ANSWER: G O O D J O B !

© 2011 The McGraw-Hill Companies, Inc. All rights reserved In Summary 26.1The retroperitoneal kidneys are composed of the outer renal cortex and inner renal medulla. Their function is to remove metabolic waste from the body 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.

© 2011 The McGraw-Hill Companies, Inc. All rights reserved In Summary (cont.) 26.3 The nephrons filter blood and form urine through three processes: glomerular filtration, tubular reabsorption, and tubular secretion Some of the components of urine include water, urea, uric acid, trace amounts of amino acids, and various ions 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.

© 2011 The McGraw-Hill Companies, Inc. All rights reserved In Summary (cont.) 26.6Urination 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. 26.7The 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.

© 2011 The McGraw-Hill Companies, Inc. All rights reserved End of Chapter 26 This too shall pass—just like a kidney stone. ~H. Madson