The Urinary System

1. 26 The Urinary System

2. Learning Outcomes 26.1 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.

3. Learning 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.

4. 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 Urinary System Organs Kidneys Ureters Bladder Urethra

5. Functions Remove metabolic waste products from the blood Secrete the hormone erythropoietin, which stimulates bone marrow to produce red blood cells Secrete the hormonerenin,which helps regulate blood pressure The Kidneys Description The kidneys are bean-shaped organs that lie behind the peritoneal cavity (retroperitoneal) on either side of the vertebral column.

6. Kidney 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

7. Kidney 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

8. Renal Corpuscles • Composed of a group of capillaries called a glomerulus • Glomerulusis surrounded by Bowman’s capsule • Blood filtration occurs in corpuscle Glomerulus Renal Tubules • Extend from the Bowman’s • capsule of a nephron • Consist of three parts: • Proximal convoluted tubule • Loop of Henle • Distal convoluted tubule Nephrons • Removes waste products from the blood • Each kidney contains about 1 million nephrons • Made of a renal corpuscle and a renal tubule

9. Afferent Arteriole Glomerulus Efferent Arteriole Peritubular Capillaries Nephrons (cont.) Blood Flow Through Nephron • Afferent arterioles deliver blood to the glomeruli • Efferent arteriolescarry blood from the glomeruli to peritubular capillaries Veins of the Kidney

10. 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!

11. Glomerulus 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

12. 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

13. Tubular Reabsorption 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

14. 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 Tubular Secretion

15. Urine Formation (cont.) • Urine composition • Mostly water • Ureaand 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

16. ANSWER: B 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 A C A Nice Job! B

17. Bladder 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

18. Previous

19. Brain stemandcerebralcortex Impulses to contract urethra; inhibit micturition impulse until ready to urinate Spinal cord Parasympathetic nerves stimulate detrusor muscle Stretch receptors Bladderdistends Urination • External urethral sphincter relaxes • Micturition reflex – impulses from pons and hypothalamus • Detrusor muscle contracts • Urine expelled

20. Urethra 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

21. trigone ureters males Apply Your Knowledge Impressive! ANSWER: 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. T F T F F T

22. Diseases and Disorders of the Urinary System

23. Diseases and Disorders of the Urinary System

24. Apply Your Knowledge Matching: ___ 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 disease ANSWER: GOOD JOB! A C E D F B H G

25. In Summary 26.1 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. 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. In Summary (cont.)

27. In 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.

28. End of Chapter 26 This too shall pass—just like a kidney stone. ~H. Madson