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The Urinary System Chapter 15 Urinary System Well, I guess you don’t have kidney stones after all. Moment of Zen KIDNEY kidneys Organs of the Urinary System ureters urinary bladder urethra 7 8 Urinary System Organs 9 Figure 25.1a 10 Functions of the Urinary System Elimination of waste products Nitrogenous wastes Toxins Drugs Functions of the Urinary System Regulate aspects of homeostasis Water balance Electrolytes Acid-base balance in the blood Blood pressure Red blood cell production Activation of vitamin D nephron renal artery renal vein Kidney Anatomy Organs of the Urinary system Kidneys Ureters Urinary bladder Urethra Figure 15.1a Location of the Kidneys Against the dorsal body wall At the level of T12 to L3 The right kidney is slightly lower than the left Attached to ureters, renal blood vessels, and nerves at renal hilus Atop each kidney is an adrenal gland Coverings of the Kidneys Renal capsule Surrounds each kidney Adipose capsule Surrounds the kidney Provides protection to the kidney Helps keep the kidney in its correct location Kidney Anatomy renal pelvis ureter renal pyramids renal cortex renal capsule renal medulla Regions of the Kidney Renal cortex – outer region Renal medulla – inside the cortex Renal pelvis – inner collecting tube Figure 15.2b Kidney Structures Medullary pyramids – triangular regions of tissue in the medulla Renal columns – extensions of cortexlike material inward Calyces – cup-shaped structures that funnel urine towards the renal pelvis Blood Flow in the Kidneys Figure 15.2c Nephrons The structural and functional units of the kidneys Responsible for forming urine Main structures of the nephrons Glomerulus Renal tubule Types of Nephrons Cortical nephrons Located entirely in the cortex Includes most nephrons Figure 15.3a Types of Nephrons Juxtamedullary nephrons Found at the boundary of the cortex and medulla Figure 15.3a Nephrons are connected to renal artery/vein and ureter. 26 Nephron Glomerulus A specialized capillary bed Attached to arterioles on both sides (maintains high pressure) Large afferent arteriole Narrow efferent arteriole Figure 15.3c Glomerulus Capillaries are covered with podocytes from the renal tubule The glomerulus sits within a glomerular capsule (the first part of the renal tubule) Figure 15.3c 30 31 Renal Tubule Glomerular (Bowman’s) capsule Proximal convoluted tubule Loop of Henle Distal convoluted tubule Figure 15.3b Peritubular Capillaries Arise from efferent arteriole of the glomerulus Normal, low pressure capillaries Attached to a venule Cling close to the renal tubule Reabsorb (reclaim) some substances from collecting tubes Urine Formation Processes Filtration Reabsorption Secretion Figure 15.4 blood filtration General Functioning of the Kidney tubular reabsorption and secretion urine “refreshed” blood Filtration Nonselective passive process Water and solutes smaller than proteins are forced through capillary walls Blood cells cannot pass out to the capillaries Filtrate is collected in the glomerular capsule and leaves via the renal tubule Reabsorption The peritubular capillaries reabsorb several materials Some water Glucose Amino acids Ions Some reabsorption is passive, most is active Most reabsorption occurs in the proximal convoluted tubule Materials Not Reabsorbed Nitrogenous waste products Urea Uric acid Creatinine Excess water Secretion – Reabsorption in Reverse Some materials move from the peritubular capillaries into the renal tubules Hydrogen and potassium ions Creatinine Materials left in the renal tubule move toward the ureter Formation of Urine Figure 15.5 Characteristics of Urine Used for Medical Diagnosis Colored somewhat yellow due to the pigment urochrome (from the destruction of hemoglobin) and solutes Sterile Slightly aromatic Normal pH of around 6 Specific gravity of 1.001 to 1.035 Ureters Slender tubes attaching the kidney to the bladder Continuous with the renal pelvis Enter the posterior aspect of the bladder Runs behind the peritoneum Peristalsis aids gravity in urine transport 43 15 The Urinary System PART A PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY EIGHTH EDITION ELAINE N. MARIEB Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Urinary Bladder Smooth, collapsible, muscular sac Temporarily stores urine Figure 15.6 Urinary Bladder Trigone – three openings Two from the ureters One to the urethrea Figure 15.6 Urinary Bladder Wall Three layers of smooth muscle (detrusor muscle) Mucosa made of transitional epithelium Walls are thick and folded in an empty bladder Bladder can expand significantly without increasing internal pressure Urethra Thin-walled tube that carries urine from the bladder to the outside of the body by peristalsis Release of urine is controlled by two sphincters Internal urethral sphincter (involuntary) External urethral sphincter (voluntary) Urethra Gender Differences Length Females – 3–4 cm (1 inch) Males – 20 cm (8 inches) Location Females – along wall of the vagina Males – through the prostate and penis Urethra Gender Differences Function Females – only carries urine Males – carries urine and is a passageway for sperm cells Micturition (Voiding) Both sphincter muscles must open to allow voiding The internal urethral sphincter is relaxed after stretching of the bladder Activation is from an impulse sent to the spinal cord and then back via the pelvic splanchnic nerves The external urethral sphincter must be voluntarily relaxed efferent arteriole afferent arteriole Glomerular Filtration Bowman’s capsule Filters blood; proteins can’t pass through glomerulus Urinary Bladder ureters external sphincters internal sphincters urethra 55 Maintaining Water Balance Normal amount of water in the human body Young adult females – 50% Young adult males – 60% Babies – 75% Old age – 45% Water is necessary for many body functions and levels must be maintained Maintaining Water Balance Water intake must equal water output Sources for water intake Ingested foods and fluids Water produced from metabolic processes Sources for water output Vaporization out of the lungs Lost in perspiration Leaves the body in the feces Urine production Maintaining Water Balance Dilute urine is produced if water intake is excessive Less urine (concentrated) is produced if large amounts of water are lost Proper concentrations of various electrolytes must be present Distribution of Body Fluid Intracellular fluid (inside cells) Extracellular fluid (outside cells) Interstitial fluid Blood plasma Figure 15.8 The Link Between Water and Salt Changes in electrolyte balance causes water to move from one compartment to another Alters blood volume and blood pressure Can impair the activity of cells Regulation of Water and Electrolyte Reabsorption Regulation is primarily by hormones Antidiuretic hormone (ADH) prevents excessive water loss in urine Aldosterone regulates sodium ion content of extracellular fluid Triggered by the rennin-angiotensin mechanism Cells in the kidneys and hypothalamus are active monitors Maintaining Water and Electrolyte Balance Figure 15.10 Maintaining Acid-Base Balance in Blood Blood pH must remain between 7.35 and 7.45 to maintain homeostasis Alkalosis – pH above 7.45 Acidosis – pH below 7.35 Most ions originate as byproducts of cellular metabolism Maintaining Acid-Base Balance in Blood Most acid-base balance is maintained by the kidneys Other acid-base controlling systems Blood buffers Respiration Blood Buffers Molecules react to prevent dramatic changes in hydrogen ion (H+) concentrations Bind to H+ when pH drops Release H+ when pH rises Three major chemical buffer systems Bicarbonate buffer system Phosphate buffer system Protein buffer system The Bicarbonate Buffer System Mixture of carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3) Bicarbonate ions (HCO3–) react with strong acids to change them to weak acids Carbonic acid dissociates in the presence of a strong base to form a weak base and water Respiratory System Controls of Acid-Base Balance Carbon dioxide in the blood is converted to bicarbonate ion and transported in the plasma Increases in hydrogen ion concentration produces more carbonic acid Respiratory System Controls of Acid-Base Balance Excess hydrogen ion can be blown off with the release of carbon dioxide from the lungs Respiratory rate can rise and fall depending on changing blood pH Renal Mechanisms of Acid-Base Balance Excrete bicarbonate ions if needed Conserve or generate new bicarbonate ions if needed Urine pH varies from 4.5 to 8.0 Developmental Aspects of the Urinary System Functional kidneys are developed by the third month Urinary system of a newborn Bladder is small Urine cannot be concentrated Developmental Aspects of the Urinary System Control of the voluntary urethral sphincter does not start until age 18 months Urinary infections are the only common problems before old age Aging and the Urinary System There is a progressive decline in urinary function The bladder shrinks with aging Urinary retention is common in males Urinalysis Ancient Greeks & Roman physicians routinely studied urine when diagnosing patients Today a urinalysis is done to check for microorganism content, as well as chemical and physical properties Physical characteristics routinely checked: color, turbidity, pH & specific gravity Urinalysis Healthy urine is sterile bacteria can enter sample from 1) incorrect sample collection or 2) infection Infection can also be caused by fungus or protozoans Electrolytes in urine have clinical implications – Ca2+, Cl-,K+, Na+ 77 78 Three congenital abnormalities results Renal agenesis: failure of one or both kidneys to develop Duplications of urinary tract Bilateral: rare, associated with other congenital anomalies, incompatible with life Unilateral: common, asymptomatic; other kidney enlarges to compensate Complete duplication: formation of extra ureter and renal pelvis Incomplete duplication: only upper part of excretory system is duplicated Malposition: one or both kidneys, associated with fusion of kidneys; horseshoe kidney; fusion of upper pole Common congenital abnormalities of kidneys and urinary tract Glomerulonephritis Inflammation of the glomeruli caused by antigenantibody reaction within the glomeruli Immune-complex glomerulonephritis Usually follows a beta-streptococcal infection Circulating antigen and antibody complexes are filtered by glomeruli and incite inflammation Leukocytes release lysosomal enzymes that cause injury to the glomeruli Occurs in SLE; immune complexes trapped in glomeruli Occurs in IgA nephropathy Anti-glomerular basement membrane (anti-GBM) glomerulonephritis: autoantibodies attack glomerular basement membrane Normal glomerulus Immune complex glomerulonephritis Anti-GBM glomerulonephritis Nephrotic Syndrome (1 of 2) Marked loss of protein in the urine Urinary excretion of protein > protein production Protein level in blood falls Causes edema due to low plasma osmotic pressure Clinical manifestations Marked leg edema Ascites Nephrotic Syndrome (2 of 2) Prognosis In children: minimal glomerular change, complete recovery In adults: a manifestation of severe progressive renal disease May result from Glomerulonephritis Diabetes (causing glomerular changes) Systemic lupus erythematosus, SLE Other kidney diseases Arteriolar Nephrosclerosis Complication of severe hypertension Renal arterioles undergo thickening from carrying blood at a much higher pressure than normal Glomeruli and tubules undergo secondary degenerative changes causing narrowing of lumen and reduction in blood flow Reduced glomerular filtration Kidneys shrink May die of renal insufficiency Diabetic Nephropathy Complication of long-standing diabetes Nodular and diffuse thickening of glomerular basement membranes (glomerulosclerosis), usually with coexisting nephrosclerosis Manifestations Progressive impairment of renal function Protein loss may lead to nephrotic syndrome No specific treatment can arrest progression of disease Progressive impairment of renal function may lead to renal failure Diffuse glomerulosclerosis Nodular glomerulosclerosis Gout Nephropathy Pathogenesis Elevated blood uric acid levels lead to ↑uric acid in tubular filtrate Urate may precipitate in Henle’s loops and collecting tubules Tubular obstruction causes damage Manifestations Impaired renal function May lead to renal failure Common in poorly-controlled gout Urate nephropathy showing multiple depressed scars Section of kidney revealing white urate deposits within renal pyramid and large urate deposit near tip of pyramid Urinary Tract Infections (1 of 2) Very common; maybe acute or chronic Most infections are caused by gram-negative bacteria Organisms contaminate perianal and genital areas and ascend urethra Conditions protective against infection Free urine flow Large urine volume Complete bladder emptying Acid urine: most bacteria grow poorly in an acidic environment Urinary Tract Infections (2 of 2) Predisposing factors Any condition that impairs free drainage of urine Stagnation of urine favors bacterial growth Injury to mucosa by kidney stone disrupts protective epithelium allowing bacteria to invade deeper tissue Introduction of catheter or instruments into bladder may carry bacteria Cystitis Affects only the bladder More common in women than men; shorter female urethra, and, in young sexually active women, sexual intercourse promotes transfer of bacteria from urethra to bladder Common in older men, because enlarged prostate interferes with complete bladder emptying Clinical manifestations Burning pain on urination Desire to urinate frequently Urine contains many bacteria and leukocytes Responds well to antibiotics May spread upward into renal pelvis and kidneys Pyelonephritis Involvement of upper urinary tract from Ascending infection from the bladder (ascending pyelonephritis) Carried to the kidneys from the bloodstream (hematogenous pyelonephritis) Clinical manifestations: similar with an acute infection Localized pain and tenderness over affected kidney Responds well to antibiotics Cystitis and pyelonephritis are frequently associated Some cases become chronic and lead to kidney failure Vesicoureteral Reflux Urine normally prevented from flowing back into the ureters during urination Failure of mechanisms allows bladder urine to reflux into ureter during voiding Predisposes to urinary tract infection Predisposes to pyelonephritis Vesicoureteral reflux Urinary Calculi (1 of 3) Stones may form anywhere in the urinary tract Predisposing factors High concentration of salts in urine saturates urine causing salts to precipitate and form calculi Uric acid in gout Calcium salts in hyperparathyroidism Urinary tract infections reduce solubility of salts in urine; clusters of bacteria are sites where urinary salts may crystallize to form stone Urinary tract obstruction causes urine stagnation, promotes stasis and infection, further increasing stone formation Urinary Calculi (2 of 3) Staghorn calculus: urinary stones that increase in size to form large branching structures that adopt to the contour of the pelvis and calyces Small stones may pass through ureters causing renal colic Some become impacted in the ureter and need to be removed Manifestations Renal colic associated with passage of stone Obstruction of urinary tract causes hydronephrosishydroureter proximal to obstruction Urinary Calculi (3 of 3) Treatment Cystoscopy: snares and removes stones lodged in distal ureter Shock wave lithotripsy: stones lodged in proximal ureter are broken into fragments that are readily excreted Large staghorn calculus of kidney Urinary Obstruction Blockage of urine outflow leads to progressive dilatation of urinary tract proximal to obstruction, eventually causes compression atrophy of kidneys Manifestations Causes Hydroureter: dilatation of ureter Hydronephrosis: dilatation of pelvis and calyces Bilateral: obstruction of bladder neck by enlarged prostate or urethral stricture Unilateral: ureteral stricture, calculus, tumor Complications: stone formation; infections Diagnosis and treatment: pyelogram, CT san Possible locations and results of urinary tract obstruction Marked hydronephrosis and hydroureter Bisected hydronephrotic kidney Foreign Bodies in Urinary Tract Usually inserted by patient May injure bladder Predispose to infection Treatment Usually removed by cystoscopy Occasionally necessary to open bladder surgically X-ray film illustrating foreign body in bladder. Renal Tubular Injury Pathogenesis Impaired renal blood flow Tubular necrosis caused by toxic drugs or chemicals Clinical manifestation Acute renal failure: oliguria, anuria Tubular function gradually recovers Treated by dialysis until function returns Renal Cysts Solitary cysts common; not associated with impairment of renal function Multiple cysts Congenital polycystic kidney disease Most common cause of multiple cysts Mendelian dominant transmission Cysts enlarge and destroy renal tissue and function Onset of renal failure by late middle age Suspected by physical examination that reveals greatly enlarged kidneys Some form cysts in liver or cerebral aneurysm Renal Tumors Cortical tumors: arise from epithelium of renal tubules Adenomas: usually small and asymptomatic Carcinomas more common Hematuria often first manifestation Invades renal vein and metastasizes into bloodstream Treated by nephrectomy Transitional cell tumor: Arise from transitional epithelium lining urinary tract Most arise from bladder epithelium Hematuria: common first manifestation Low grade malignancy; good prognosis Nephroblastoma (Wilms Tumor) Uncommon; highly malignant; affects infants and children Diagnosis Urinalysis Urine culture and sensitivity tests Blood chemistry tests Clearance tests X-ray, ultrasound, cystoscopy Renal biopsy Treatment: nephrectomy; radiotherapy; chemotherapy Renal Failure (Uremia) (1 of 2) Retention of excessive byproducts of protein metabolism in the blood Acute renal failure Causes: tubular necrosis from impaired blood flow to kidneys or effects of toxic drugs Renal function usually returns Chronic renal failure From progressive, chronic kidney disease; > 50% from chronic glomerulonephritis Others include congenital polycystic kidney disease, nephrosclerosis, diabetic nephropathy Renal Failure (Uremia) (2 of 2) Clinical manifestations Weakness, loss of appetite, nausea, vomiting Anemia Toxic manifestations from retained waste products Edema: retention of salt and water Hypertension Treatment Hemodialysis Hypertension Hemodialysis Substitutes for the functions of the kidneys by removing waste products from patient’s blood Waste products in patient’s blood diffuse across a semipermeable membrane into a solution (dialysate) into the other side of the membrane Two types Extracorporeal dialysis (more common): patient’s circulation connected to an artificial kidney machine Peritoneal dialysis (less common): patient’s own peritoneum is used as the dialyzing membrane Function 1. Remove nitrogenous wastes 2. Maintain electrolyte, acid-base, and fluid balance of blood 3. Homeostatic organ 4. Acts as blood filter 5. Release hormones: calcitriol & erythropoietin Kidneys as Filters • Diuretic- loose water; coffee, alcohol • Antidiuretic- retain water; ADH • Aldosterone- sodium & water reabsorption, and K+ excretion • GFR= 180 liters (50 gal) of blood/day • 178-179 liters are reabsorbed back into blood • Excrete a protein free filtrate Maintaining Chemical Homeostasis The Urinary System The Urinary System Nitrogenous Wastes urea uric acid ammonia efferent arteriole afferent arteriole glomerulus artery peritubular capillaries loop of Henle vein Bowman’s capsule proximal convoluted tubule distal convoluted tubule collecting duct Each kidney contains over 1 million nephrons and thousands of collecting ducts Glomerulus DCT renal cortex PCT renal medulla Collecting duct Loop of Henle Composition of Glomerular Filtrate • Water • Small Soluble Organic Molecules • Mineral Ions Proximal Convoluted Tubule Reabsorbs: water, glucose, amino acids, and sodium. • • • • 65% of Na+ is reabsorbed 65% of H2O is reabsorbed 90% of filtered bicarbonate (HCO3-) 50% of Cl- and K+ Loop of Henle Creates a gradient of increasing sodium ion concentration towards the end of the loop within the interstitial fluid of the renal pyramid. • 25% Na+ is reabsorbed in the loop • 15% water is reabsorbed in the loop • 40% K is reabsorbed in the loop Distal Convoluted Tubule Under the influence of the hormone aldosterone, reabsorbs sodium and secretes potassium. Also regulates pH by secreting hydrogen ion when pH of the plasma is low. • only 10% of the filtered NaCl and 20% of water remains Collecting Duct Allows for the osmotic reabsorption of water. ADH (antidiuretic hormone)- makes collecting ducts more permeable to water-- produce concentrated urine Urine Water- 95% Nitrogenous waste: • urea • uric acid • creatinine Ions: • sodium • potassium • sulfate • phosphate From the original 1800 g NaCl, only 10 g appears in the urine Hormonal Control of Kidney Function Hormonal Control of Kidney Function high plasma solute concentration low blood volume heart receptors hypothalamus Hormonal Control of Kidney Function hypothalamus posterior pituitary antidiuretic hormone collecting ducts Hormonal Control of Kidney Function Hormonal Control of Kidney Function reduced blood pressure and glomerular filtrate juxtaglomerular apparatus renin Hormonal Control of Kidney Function angiotensinogen angiotensin I angiotensin II renin Hormonal Control of Kidney Function angiotensin II adrenal cortex aldosterone convoluted tubules Bladder 1. Mucosa (transitional epithelium) 2. Muscular layer (detrusor muscle): 3 layers of smooth muscle 3. Fibrous adventia Sphincter Muscles on Bladder Internal urethral sphincter: • Smooth muscle • Involuntary control • More superiorly located External Urethral sphincter: • Skeletal muscle • Voluntary control • Posteriorly located Diuresis (Micturition) When bladder fills with 200 ml of urine, stretch receptors transmit impulses to the CNS and produce a reflex contraction of the bladder (PNS) When is incontinence normal? Distension of the Urinary Bladder Urinalysis Why do doctors ask for a urine sample? characteristics: • smell- ammonia-like • pH- 4.5-8, ave 6.0 • specific gravity– more than 1.0; ~1.0011.003 • color- affected by what we eat: salty foods, vitamins Odor odor- normal is ammonia-like diabetes mellitus- smells fruity or acetone like due to elevated ketone levels diabetes insupidus- yucky asparagus--- pH- range 4.5-8 ave 6.0 vegetarian diet- urine is alkaline protein rich and wheat dieturine is acidic Color Color- pigment is urochrome Yellow color due to metabolic breakdown of hemoglobin (by bile or bile pigments) Beets or rhubarb- might give a urine pink or smoky color Vitamins- vitamin C- bright yellow Infection- cloudy Specific Gravity Water: s.g. = 1g/liter; Urine: s.g. ~ 1.001 to 1.030 Pyelonephritus- urine has high s.g.; form kidney stones Diabetes insipidus- urine has low s.g.; drinks excessive water; injury or tumor in pituitary Abnormal Constitutes of Urine Glucose- when present in urine condition called glycosuria (nonpathological) [glucose not normally found in urine] Indicative of: • Excessive carbohydrate intake • Stress • Diabetes mellitus Abnormal Constitutes of Urine Albumin-abnormal in urine; it’s a very large molecule, too large to pass through glomerular membrane > abnormal increase in permeability of membrane Albuminuria- nonpathological conditionsexcessive exertion, pregnancy, overabundant protein intake-- leads to physiologic albuminuria Pathological condition- kidney trauma due to blows, heavy metals, bacterial toxin Abnormal Constitutes of Urine Ketone bodies- normal in urine but in small amts Ketonuria- find during starvation, using fat stores Ketonuria is couples w/a finding of glycosuria-- which is usually diagnosed as diabetes mellitus RBC-hematuria HemoglobinHemoglobinuria- due to fragmentation or hemolysis of RBC; conditions: hemolytic anemia, transfusion reaction, burns or renal disease Abnormal Constitutes of Urine Bile pigmentsBilirubinuria (bile pigment in urine)- liver pathology such as hepatitis or cirrhosis WBCPyuria- urinary tract infection; indicates inflammation of urinary tract Casts- hardened cell fragments, cylindrical, flushed out of urinary tract WBC casts- pyelonephritus RBC casts- glomerulonephritus Fatty casts- renal damage INQUIRY 1. 2. 3. 4. 5. List several functions of the kidneys. What does the glomerulus do? What are several constitutes you should not find in urine? What is specific gravity? What two hormones effect fluid volume and sodium concentration in the urine? 6. Where are the pyramids located in the kidney? 7. What vessel directs blood into the glomerulus? 8. Where does most selective reabsorption occur in the nephron?