Urinary System Organs PDF

Copyright © 2010 Pearson Education, Inc.  Urinary System Organs Kidneys are major excretory organs Urinary bladder is the temporary storage reservoir for urine Ureters transport urine from the kidneys to the bladder Urethra transports urine out of the bo...

Copyright © 2010 Pearson Education, Inc.  Urinary System Organs Kidneys are major excretory organs Urinary bladder is the temporary storage reservoir for urine Ureters transport urine from the kidneys to the bladder Urethra transports urine out of the body Copyright © 2010 Pearson Education, Inc.  Hepatic veins (cut) Esophagus (cut) Inferior vena cava Renal artery Adrenal gland Renal hilum Aorta Renal vein Kidney Iliac crest Loading… Ureter Rectum (cut) Uterus (part of female Urinary reproductive bladder system) Urethra Copyright © 2010 Pearson Education, Inc.  Kidney Functions Removal of toxins, metabolic wastes, and excess ions from the blood Regulation of blood volume, chemical composition, and pH Copyright © 2010 Pearson Education, Inc.  Kidney Functions Gluconeogenesis during prolonged fasting Endocrine functions Renin: regulation of blood pressure and kidney function Loading… Erythropoietin: regulation of RBC production Activation of vitamin D Copyright © 2010 Pearson Education, Inc.  Nephrons Structural and functional units that form urine ~1 million per kidney Two main parts 1. Glomerulus: a tuft of capillaries 2. Renal tubule: begins as cup-shaped glomerular (Bowman’s) capsule surrounding the glomerulus Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc.  Figure 18.2 Anatomy of a kidney. Renal cortex Renal medulla Renal pyramid Renal artery Renal papilla Renal pelvis Renal vein Minor calyx Renal medulla Renal cortex Minor calyx Major calyx Bowman's capsule Ureter Blood vessels Nephron Collecting duct Copyright © 2010 Pearson Education, Inc.  Afferent arteriole Glomerular capillaries Efferent Cortica arteriole l radiate Glomerular artery capsule Rest of renal tubule containing filtrate Peritubula r Three major capillary renal processes: Glomerular filtration To cortical radiate vein Tubular reabsorption Tubular secretion Urine Copyright © 2010 Pearson Education, Inc.  Figure 18.5 The juxtaglomerular apparatus. Bowman's capsule Juxtaglomerular Glomerular capillary Efferent arteriole apparatus Lumen of Proximal Bowman's Distal tubule tubule capsule Afferent arteriole Efferent arteriole Distal tubule Macula densa Direction of Loop of blood flow Henle Afferent arteriole Granular cells (juxtaglomerular cells) Copyright © 2010 Pearson Education, Inc.  Efferent Glomerular arteriole capsule Glomerulu s Afferent arteriole Foot Parietal layer processes of Podocyte cell of podocytes body (visceral glomerular capsule Capsula layer) r Red blood space cell Proximal Efferent arteriole tubule cell Juxtaglomerular apparatus Loading… Macula densa cells of the ascending limb Lumens of of loop of Henle glomerular Extraglomerular capillaries mesangial cells Endothelial Granular cells cell of glomerular Afferent capillary Mesangial cells arteriole between capillaries Juxtaglomerular Renal apparatus corpuscle Copyright © 2010 Pearson Education, Inc.  Filtration Membrane Allows passage of water and solutes smaller than most plasma proteins Fenestrations prevent filtration of blood cells Negatively charged basement membrane repels large anions such as plasma proteins Slit diaphragms also help to repel macromolecules Copyright © 2010 Pearson Education, Inc.  Filtration Membrane Glomerular mesangial cells Engulf and degrade macromolecules Can contract to change the total surface area available for filtration Copyright © 2010 Pearson Education, Inc.  Glomerular Filtration Passive mechanical process driven by hydrostatic pressure The glomerulus is a very efficient filter because Its filtration membrane is very permeable and it has a large surface area Glomerular blood pressure is higher (55 mm Hg) than other capillaries Molecules >5 nm are not filtered (e.g., plasma proteins) and function to maintain colloid osmotic pressure of the blood Copyright © 2010 Pearson Education, Inc.  Filtration membrane Capillary endothelium Capillar Basement membrane y Foot processes of podocyte of glomerular capsule Filtration slit Slit diaphragm Plasm Filtrate a in capsular Fenestratio space Foot n processes (pore) of podocyte (c) Three parts of the filtration membrane Copyright © 2010 Pearson Education, Inc.  Afferent arteriol Glomerula e r capsule Glomerular (blood) hydrostatic 10 pressure mm (HPg =colloid 55 mmosmotic Hg) Hg Blood pressure Net (Opg = 30hydrostatic mm Hg) filtration Capsular pressur pressure e (HPc = 15 mm Hg) Copyright © 2010 Pearson Education, Inc.  Renal Tubule Glomerular capsule Parietal layer: simple squamous epithelium Visceral layer: branching epithelial podocytes Extensions terminate in foot processes that cling to basement membrane Filtration slits allow filtrate to pass into the capsular space Copyright © 2010 Pearson Education, Inc.  Glomerular Filtration Rate (GFR) Volume of filtrate formed per minute by the kidneys (120–125 ml/min) Governed by (and directly proportional to) Total surface area available for filtration Filtration membrane permeability NFP Copyright © 2010 Pearson Education, Inc.  Regulation of Glomerular Filtration GFR is tightly controlled by two types of mechanisms Intrinsic controls (renal autoregulation) Act locally within the kidney Extrinsic controls Nervous and endocrine mechanisms that maintain blood pressure, but affect kidney function Copyright © 2010 Pearson Education, Inc.  Intrinsic Controls Maintains a nearly constant GFR when MAP is in the range of 80–180 mm Hg Two types of renal autoregulation Myogenic mechanism (Chapter 19) Tubuloglomerular feedback mechanism, which senses changes in the juxtaglomerular apparatus Copyright © 2010 Pearson Education, Inc.  Intrinsic Controls: Myogenic Mechanism BP constriction of afferent arterioles Helps maintain normal GFR Protects glomeruli from damaging high BP BP dilation of afferent arterioles Helps maintain normal GFR Copyright © 2010 Pearson Education, Inc.  Intrinsic Controls: Tubuloglomerular Feedback Mechanism Flow-dependent mechanism directed by the macula densa cells If GFR increases, filtrate flow rate increases in the tubule Filtrate NaCl concentration will be high because of insufficient time for reabsorption Copyright © 2010 Pearson Education, Inc.  Intrinsic Controls: Tubuloglomerular Feedback Mechanism Macula densa cells of the JGA respond to NaCl by releasing a vasoconstricting chemical that acts on the afferent arteriole GFR The opposite occurs if GFR decreases. Copyright © 2010 Pearson Education, Inc.  Extrinsic Controls: Sympathetic Nervous System Under normal conditions at rest Renal blood vessels are dilated Renal autoregulation mechanisms prevail Copyright © 2010 Pearson Education, Inc.  Extrinsic Controls: Sympathetic Nervous System Under extreme stress Norepinephrine is released by the sympathetic nervous system Epinephrine is released by the adrenal medulla Both cause constriction of afferent arterioles, inhibiting filtration and triggering the release of renin Copyright © 2010 Pearson Education, Inc.  Extrinsic Controls: Renin-Angiotensin Mechanism Triggered when the granular cells of the JGA release renin angiotensinogen (a plasma globulin) renin angiotensin I angiotensin converting enzyme (ACE) angiotensin II Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc.  Effects of Angiotensin II 1. Constricts arteriolar smooth muscle, causing MAP to rise 2. Stimulates the reabsorption of Na+ Acts directly on the renal tubules Triggers adrenal cortex to release aldosterone 3. Stimulates the hypothalamus to release ADH and activates the thirst center Copyright © 2010 Pearson Education, Inc.  Effects of Angiotensin II 1. Constricts efferent arterioles, decreasing peritubular capillary hydrostatic pressure and increasing fluid reabsorption 2. Causes glomerular mesangial cells to Loading… contract, decreasing the surface area available for filtration Copyright © 2010 Pearson Education, Inc.  Extrinsic Controls: Renin-Angiotensin Mechanism Triggers for renin release by granular cells Reduced stretch of granular cells (MAP below 80 mm Hg) Stimulation of the granular cells by activated macula densa cells Direct stimulation of granular cells via 1- adrenergic receptors by renal nerves Copyright © 2010 Pearson Education, Inc.  SYSTEMIC BLOOD PRESSURE (– Blood pressure in Granular cells of ) in Baroreceptors GF afferent arterioles; GFR R juxtaglomerular blood vessels of apparatus of systemic circulation kidney Releas Stretch of smooth Filtrate flow and e (+ muscle in walls of NaCl in ascending (+ Reni (+ ) ) ) Sympathetic afferent arterioles limb of Henle’s loop n nervous system Catalyzes cascade Targets resulting in conversion Vasodilation of afferent Angiotensinoge Angiotensin II arterioles n (+ (+ (+ Macula densa cells ) Adrenal Systemic ) ) of JG apparatus cortex arterioles Releases of kidney Aldosteron Vasoconstriction; Release of e peripheral resistance Targets vasoactive chemical inhibited Kidney Vasodilation of tubules afferent arterioles Na+ (+) Stimulate reabsorption; (– sInhibit water follows ) Increas s Decreas e GFR Blood volume e Systemic blood pressure Myogenic mechanism Tubuloglomerular Hormonal (renin-angiotensin) mechanism of Neural controls of autoregulation autoregulation mechanism Intrinsic mechanisms directly regulate GFR despite Extrinsic mechanisms indirectly regulate GFR moderate changes in blood pressure (between 80 by maintaining systemic blood pressure, which and 180 mm Hg mean arterial pressure). drives filtration in the kidneys. Copyright © 2010 Pearson Education, Inc.  Other Factors Affecting GRF Prostaglandin E2 Vasodilator that counteracts vasoconstriction by norepinephrine and angiotensin II Prevents renal damage when peripheral resistance is increased Copyright © 2010 Pearson Education, Inc.  Other Factors Affecting GRF Intrarenal angiotensin II Reinforces the effects of hormonal angiotensin II Adenosine A vasoconstrictor of renal vasculature Copyright © 2010 Pearson Education, Inc.  Tubular Reabsorption A selective transepithelial process All organic nutrients are reabsorbed Water and ion reabsorption are hormonally regulated Includes active and passive process Two routes Transcellular Paracellular Copyright © 2010 Pearson Education, Inc.  Tubular Reabsorption Paracellular route Between cells Limited to water movement and reabsorption of Ca2+, Mg2+, K+, and some Na+ in the PCT where tight junctions are leaky Copyright © 2010 Pearson Education, Inc.  Tubular Reabsorption Transcellular route Luminal membranes of tubule cells Cytosol of tubule cells Basolateral membranes of tubule cells Endothelium of peritubular capillaries Copyright © 2010 Pearson Education, Inc.  Movement via the 3 Transport across the basolateral The paracellular route transcellular route involves: involves: membrane. (Often involves the lateral intercellular spaces because Movement through 1 Transport across the membrane transporters transport ions leaky tight junctions, luminal membrane. into these spaces.) particularly in the PCT. 2 Diffusion through the 4 Movement through the interstitial cytosol. fluid and into the capillary. Tight Lateral intercellular junction space Filtrate Tubule Interstitia in cell l Peri- tubule fluid Capillary tubular lumen endothelia capillar l y cell Paracellula H2O r 1 2 3 4 Luminal Transcellula membran r e 1 Transcellula 3 4 r 2 Solutes 3 4 Active Paracellula transport Basolateral r membrane Passive s transport Copyright © 2010 Pearson Education, Inc.  Sodium Reabsorption Na+ (most abundant cation in filtrate) Primary active transport out of the tubule cell by Na+-K+ ATPase in the basolateral membrane Na+ passes in through the luminal membrane by secondary active transport or facilitated diffusion mechanisms Copyright © 2010 Pearson Education, Inc.  Sodium Reabsorption Low hydrostatic pressure and high osmotic pressure in the peritubular capillaries Promotes bulk flow of water and solutes (including Na+) Copyright © 2010 Pearson Education, Inc.  Reabsorption of Nutrients, Water, and Ions Na+ reabsorption provides the energy and the means for reabsorbing most other substances Organic nutrients are reabsorbed by secondary active transport Transport maximum (Tm) reflects the number of carriers in the renal tubules available When the carriers are saturated, excess of that substance is excreted Copyright © 2010 Pearson Education, Inc.  Reabsorption of Nutrients, Water, and Ions Water is reabsorbed by osmosis (obligatory water reabsorption), aided by water-filled pores called aquaporins Cations and fat-soluble substances follow by diffusion Copyright © 2010 Pearson Education, Inc.  1 At the basolateral membrane, Na+ is pumped into the interstitial space by the Na+-K+ ATPase. Active Na+ transport Nucleu creates concentration gradients Filtrate Interstitia Peri- s that drive: in tubule Tubule l tubular 2 “Downhill” Na+ entry at the lumen cell fluid capillar luminal membrane. y 3 Reabsorption of organic Na 2 nutrients and certain ions by + 3Na 3Na cotransport at the luminal + 1 + Glucose membrane. 2K 2K Amino 3 4 Reabsorption of water by + + acids osmosis. Water reabsorption K Some increases the concentration of + ions the solutes that are left 4 Vitamins behind. These solutes can H2 then be reabsorbed as O 5 they move down their Lipid-soluble concentration gradients: substances 5 Lipid-soluble 6 Cl–, Ca2+, Cl substances diffuse by the K+ Paracellula – transcellular route. Tight and other r 6 Cl– (and other anions), junction ions, urea K+, and urea diffuse by the Primary active transport Transport protein route Secondary active transport Ion channel or aquaporin paracellular route. Passive transport (diffusion) Copyright © 2010 Pearson Education, Inc.  Reabsorptive Capabilities of Renal Tubules and Collecting Ducts PCT Site of most reabsorption 65% of Na+ and water All nutrients Ions Small proteins Copyright © 2010 Pearson Education, Inc.  Reabsorptive Capabilities of Renal Tubules and Collecting Ducts Loop of Henle Descending limb: H2O Ascending limb: Na+, K+, Cl Copyright © 2010 Pearson Education, Inc.  Reabsorptive Capabilities of Renal Tubules and Collecting Ducts DCT and collecting duct Reabsorption is hormonally regulated Ca2+ (PTH) Water (ADH) Na+ (aldosterone and ANP) Copyright © 2010 Pearson Education, Inc.  Reabsorptive Capabilities of Renal Tubules and Collecting Ducts Mechanism of aldosterone Targets collecting ducts (principal cells) and distal DCT Promotes synthesis of luminal Na+ and K+ channels Promotes synthesis of basolateral Na+-K+ ATPases Copyright © 2010 Pearson Education, Inc.  Tubular Secretion Reabsorption in reverse K+, H+, NH4+, creatinine, and organic acids move from peritubular capillaries or tubule cells into filtrate Disposes of substances that are bound to plasma proteins Copyright © 2010 Pearson Education, Inc.  Tubular Secretion Eliminates undesirable substances that have been passively reabsorbed (e.g., urea and uric acid) Rids the body of excess K+ Controls blood pH by altering amounts of H+ or HCO3– in urine Copyright © 2010 Pearson Education, Inc.  Regulation of Urine Concentration and Volume Osmolality Number of solute particles in 1 kg of H2O Reflects ability to cause osmosis Copyright © 2010 Pearson Education, Inc.  Regulation of Urine Concentration and Volume Osmolality of body fluids Expressed in milliosmols (mOsm) The kidneys maintain osmolality of plasma at ~300 mOsm, using countercurrent mechanisms Copyright © 2010 Pearson Education, Inc.  Countercurrent Mechanism Occurs when fluid flows in opposite directions in two adjacent segments of the same tube Filtrate flow in the loop of Henle (countercurrent multiplier) Blood flow in the vasa recta (countercurrent exchanger) Copyright © 2010 Pearson Education, Inc.  Countercurrent Mechanism Role of countercurrent mechanisms Establish and maintain an osmotic gradient (300 mOsm to 1200 mOsm) from renal cortex through the medulla Allow the kidneys to vary urine concentration Copyright © 2010 Pearson Education, Inc.  Cortex Medulla Copyright © 2010 Pearson Education, Inc.  Countercurrent Multiplier: Loop of Henle Descending limb Freely permeable to H2O, which passes out of the filtrate into the hyperosmotic medullary interstitial fluid Filtrate osmolality increases to ~1200 mOsm Copyright © 2010 Pearson Education, Inc.  Countercurrent Multiplier: Loop of Henle Ascending limb Impermeable to H2O Selectively permeable to solutes Na+ and Cl– are passively reabsorbed in the thin segment, actively reabsorbed in the thick segment Filtrate osmolality decreases to 100 mOsm Copyright © 2010 Pearson Education, Inc.  Osmolality of interstitial fluid (mOsm) Filtrate entering the loop of Henle is H2 NaC Corte Active transport isosmotic to both O I x Passive transport blood plasma and H2 NaC Water cortical interstitial O I impermeable fluid. H2 NaC O I The descending limb: H2 NaC Outer Permeable to H2O O I medull Impermeable to NaCl H2 a As filtrate flows, it O NaC becomes increasingly I H2 concentrated as H2O O leaves the tubule by H2 osmosis. The filtrate O Inner osmolality increases from 300 to 1200 mOsm. medull Loop of Henle a The ascending limb: (a) Countercurrent multiplier. Impermeable to H2O The long loops of Henle of the Permeable to NaCl juxtamedullary nephrons Filtrate becomes increasingly dilute as NaCl leaves, eventually becoming create the medullary hypo-osmotic to blood at 100 mOsm in the cortex. NaCl leaving the osmotic gradient. ascending limb increases the osmolality of the medullary interstitial fluid. Copyright © 2010 Pearson Education, Inc.  Video 1 Copyright © 2010 Pearson Education, Inc.  Urea Recycling Urea moves between the collecting ducts and the loop of Henle Secreted into filtrate by facilitated diffusion in the ascending thin segment Reabsorbed by facilitated diffusion in the collecting ducts deep in the medulla Contributes to the high osmolality in the medulla Copyright © 2010 Pearson Education, Inc.  Countercurrent Exchanger: Vasa Recta The vasa recta Maintain the osmotic gradient Deliver blood to the medullary tissues Protect the medullary osmotic gradient by preventing rapid removal of salt, and by removing reabsorbed H2O Copyright © 2010 Pearson Education, Inc.  Figure 18.6b Blood supply to the kidneys. Efferent arteriole Glomerulus Peritubular capillaries Afferent arteriole Interlobular artery Cortex Arcuate artery Medulla Arcuate vein Interlobular vein Vasa recta Copyright © 2010 Pearson Education, Inc.  Osmolality Blood from Passive transport of interstitial efferent fluid To vein (mOsm) arteriole NaC NaC Corte I I x H2O H2O NaC NaC I I H2O H2O Outer medull a NaC NaC I I H2O H2O NaC NaC I I Inner H2O H2O medull a Vasa recta The vasa recta: (b) Countercurrent exchanger. Highly permeable to H2O and solute The vasa recta preserve the Nearly isosmotic to interstitial fluid due to sluggish blood flow medullary gradient while Blood becomes more concentrated as it descends deeper into removing reabsorbed water the medulla and less concentrated as it approaches the cortex. and solutes. Copyright © 2010 Pearson Education, Inc.  Formation of Dilute Urine Filtrate is diluted in the ascending loop of Henle In the absence of ADH, dilute filtrate continues into the renal pelvis as dilute urine Na+ and other ions may be selectively removed in the DCT and collecting duct, decreasing osmolality to as low as 50 mOsm Copyright © 2010 Pearson Education, Inc.  Active transport Passive transport Collecting duct Descending limb DC of loop of Henle T Corte x NaC I H2 NaC O Outer I medull a NaC I H2 Ure O a Inner medull a Large volume (a) Absence of ADH of dilute urine Copyright © 2010 Pearson Education, Inc.  Formation of Concentrated Urine Depends on the medullary osmotic gradient and ADH ADH triggers reabsorption of H2O in the collecting ducts Facultative water reabsorption occurs in the presence of ADH so that 99% of H2O in filtrate is reabsorbed Copyright © 2010 Pearson Education, Inc.  Active transport Passive transport Collecting duct H2 Descending O limb of loop of Henle H2 DC O T Corte x H2 NaC O I H2 O H2 NaC O Outer I medull H2 a NaC Ure O I a H2 H2 O Ure O Inner a H2 medull O a Small volume of (b) Maximal ADH concentrated urine Copyright © 2010 Pearson Education, Inc.  Diuretics Chemicals that enhance the urinary output Osmotic diuretics: substances not reabsorbed, (e.g., high glucose in a diabetic patient) ADH inhibitors such as alcohol Substances that inhibit Na+ reabsorption and obligatory H2O reabsorption such as caffeine and many drugs Copyright © 2010 Pearson Education, Inc.  Milliosmol Na+ (65%) H2O (65%) and s Corte x Glucose many ions Amino (e.g. (a) (d) acids Cl– and K+) 30 0 (e) Outer (b) medull a (c) 60 0 Some drugs H+, HCO3 NH4 – Inner + medull Blood pH regulation a (a) Proximal convoluted tubule: 1200 65% of filtrate volume reabsorbed Na+, glucose, amino acids, and other nutrients actively transported; H2O and many ions follow passively H+ and NH4+ secretion and HCO3– reabsorption to Active transport maintain blood pH (see Chapter 26) (primary or Passive Some drugs are secreted secondary) transport Copyright © 2010 Pearson Education, Inc.  Milliosmol Corte s x (d) (a) 30 0 (e) Outer H2 medull a (b) O (c) 60 0 (b) Descending limb of loop Inner of Henle medull a Freely permeable to H2O 1200 Not permeable to NaCl Filtrate becomes increasingly Active concentrated as H2O leaves by transport (primary or osmosis Passive secondary) transport Copyright © 2010 Pearson Education, Inc.  Milliosmol Corte s x Na (d) Cl + (a) K – 30 0 + (e) Outer (b) Ure medull a a Na (c) 60 C +l 0 – Inner (c) Ascending limb of loop of Henle medull a Impermeable to H2O 1200 Permeable to NaCl Filtrate becomes Active increasingly dilute as salt is transport (primary or reabsorbed Passive secondary) transport Copyright © 2010 Pearson Education, Inc.  Milliosmol Na+; aldosterone- s Corte x regulated (d) Ca2+; PTH-regulated (a) 30 Cl–; follows Na+ 0 (e) Outer (b) medull a (c) 60 0 Inner medull a (d) Distal convoluted tubule 1200 Na+ reabsorption regulated by aldosterone Ca2+ reabsortion regulated by Active transport parathyroid hormone (PTH) (primary or Cl– cotransported with Na+ Passive secondary) transport Copyright © 2010 Pearson Education, Inc.  Milliosmol Corte s H2O x regulated (a) (d) by ADH 30 Regulated 0 by Urea; (e) aldosterone: Na increase Outer (b) +K medull d a Blood pH + by ADH (c) 60 regulation 0 H + HCO3 Inner medull – a NH4 1200 + (e) Collecting duct H2O reabsorption through aquaporins regulated by ADH Na+ reabsorption and K+ secretion regulated by aldosterone Active transport H+ and HCO3– reabsorption or secretion (primary or secondary) to maintain blood pH (see Chapter 26) Passive transport Urea reabsorption Copyright © 2010 Pearson Education, Inc. increased by ADH Copyright © 2010 Pearson Education, Inc.  Renal Clearance Volume of plasma cleared of a particular substance in a given time Renal clearance tests are used to Determine GFR Detect glomerular damage Follow the progress of renal disease Copyright © 2010 Pearson Education, Inc.  Renal Clearance RC = UV/P RC = renal clearance rate (ml/min) U = concentration (mg/ml) of the substance in urine V = flow rate of urine formation (ml/min) P = concentration of the same substance in plasma Copyright © 2010 Pearson Education, Inc.  Renal Clearance For any substance freely filtered and neither reabsorbed nor secreted by the kidneys (e.g., insulin), RC = GFR = 125 ml/min If RC < 125 ml/min, the substance is reabsorbed If RC = 0, the substance is completely reabsorbed If RC > 125 ml/min, the substance is secreted (most drug metabolites) Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc.  Abnormal Urinary Constituents Table 25.2 Abnormal Urinary Constituents Substance Name of Condition Possible Causes Glucose Glycosuria Diabetes mellitus Proteins Proteinuria, Nonpathological: excessive physical exertion, pregnancy albuminuria Pathological (over 150 mg/day): glomerulonephritis, severe hypertension, heart failure, often an initial sign of renal disease Ketone bodies Ketonuria Excessive formation and accumulation of ketone bodies, as in starvation and untreated diabetes mellitus Hemoglobin Hemoglobinuria Various: transfusion reaction, hemolytic anemia, severe burns, etc. Bile pigments Bilirubinuria Liver disease (hepatitis, cirrhosis) or obstruction of bile ducts from liver or gallbladder Erythrocytes Hematuria Bleeding urinary tract (due to trauma, kidney stones, infection, or cancer) Leukocytes (pus) Pyuria Urinary tract infection Copyright © 2010 Pearson Education, Inc.  Physical Characteristics of Urine Color and transparency Clear, pale to deep yellow (due to urochrome) Drugs, vitamin supplements, and diet can alter the color Cloudy urine may indicate a urinary tract infection Copyright © 2010 Pearson Education, Inc.  Physical Characteristics of Urine Odor Slightly aromatic when fresh Develops ammonia odor upon standing May be altered by some drugs and vegetables Copyright © 2010 Pearson Education, Inc.  Physical Characteristics of Urine pH Slightly acidic (~pH 6, with a range of 4.5 to 8.0) Diet, prolonged vomiting, or urinary tract infections may alter pH Specific gravity 1.001 to 1.035, dependent on solute concentration Copyright © 2010 Pearson Education, Inc.  Chemical Composition of Urine 95% water and 5% solutes Nitrogenous wastes: urea, uric acid, and creatinine Other normal solutes Na+, K+, PO43–, and SO42–, Ca2+, Mg2+ and HCO3– Abnormally high concentrations of any constituent may indicate pathology Copyright © 2010 Pearson Education, Inc.  Ureters Convey urine from kidneys to bladder Retroperitoneal Enter the base of the bladder through the posterior wall As bladder pressure increases, distal ends of the ureters close, preventing backflow of urine Copyright © 2010 Pearson Education, Inc.  Ureters Three layers of wall of ureter 1. Lining of transitional epithelium 2. Smooth muscle muscularis Contracts in response to stretch 3. Loading… Outer adventitia of fibrous connective tissue Copyright © 2010 Pearson Education, Inc.  Renal Calculi Kidney stones form in renal pelvis Crystallized calcium, magnesium, or uric acid salts Larger stones block ureter, cause pressure and pain in kidneys May be due to chronic bacterial infection, urine retention, Ca2+ in blood, pH of urine Copyright © 2010 Pearson Education, Inc.  Urinary Bladder Muscular sac for temporary storage of urine Retroperitoneal, on pelvic floor posterior to pubic symphysis Males—prostate gland surrounds the neck inferiorly Females—anterior to the vagina and uterus Copyright © 2010 Pearson Education, Inc.  Urinary Bladder Layers of the bladder wall 1. Transitional epithelial mucosa 2. Thick detrusor muscle (three layers of smooth muscle) 3. Fibrous adventitia (peritoneum on superior surface only) Copyright © 2010 Pearson Education, Inc.  Urinary Bladder Collapses when empty; rugae appear Expands and rises superiorly during filling without significant rise in internal pressure Copyright © 2010 Pearson Education, Inc.  Urethra Muscular tube Lining epithelium Mostly pseudostratified columnar epithelium, except Transitional epithelium near bladder Stratified squamous epithelium near external urethral orifice Copyright © 2010 Pearson Education, Inc.  Urethra Sphincters Internal urethral sphincter Involuntary (smooth muscle) at bladder-urethra junction Contracts to open External urethral sphincter Voluntary (skeletal) muscle surrounding the urethra as it passes through the pelvic floor Copyright © 2010 Pearson Education, Inc.  Micturition Urination or voiding Three simultaneous events 1. Contraction of detrusor muscle by ANS 2. Opening of internal urethral sphincter by ANS 3. Opening of external urethral sphincter by somatic nervous system Copyright © 2010 Pearson Education, Inc.  Micturition Pontine control centers mature between ages 2 and 3 1. Pontine storage center inhibits micturition: Inhibits parasympathetic pathways Excites sympathetic and somatic efferent pathways 2. Pontine micturition center promotes micturition: Excites parasympathetic pathways Inhibits sympathetic and somatic efferent pathways Copyright © 2010 Pearson Education, Inc. Figure 25.23 Control of Micturition Copyright © 2016 Pearson Education, Inc. All Rights Reserved Video 2 Copyright © 2016 Pearson Education, Inc. All Rights Reserved  Exit Ticket 1. 2. 3. What topic if any did you have difficulty understanding? Copyright © 2010 Pearson Education, Inc.