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Chapter 26Chapter 26The Urinary SystemThe Urinary System

Kidneys, ureters, urinary Kidneys, ureters, urinary bladder & urethrabladder & urethra

Urine flows from each Urine flows from each kidney, down its ureter kidney, down its ureter to the bladder and to the to the bladder and to the outside via the urethraoutside via the urethra

Filter the blood and Filter the blood and return most of water and return most of water and solutes to the solutes to the bloodstreambloodstream

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Overview of Kidney Overview of Kidney FunctionsFunctions

Regulation of blood ionic compositionRegulation of blood ionic composition Na+, K+, Ca+2, Cl- and phosphate ionsNa+, K+, Ca+2, Cl- and phosphate ions

Regulation of blood pH, osmolarity & Regulation of blood pH, osmolarity & glucoseglucose

Regulation of blood volumeRegulation of blood volume conserving or eliminating waterconserving or eliminating water

Regulation of blood pressureRegulation of blood pressure secreting the enzyme reninsecreting the enzyme renin adjusting renal resistanceadjusting renal resistance

Release of erythropoietin & calcitriolRelease of erythropoietin & calcitriol Excretion of wastes & foreign substancesExcretion of wastes & foreign substances

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External Anatomy of KidneyExternal Anatomy of Kidney Paired kidney-bean-Paired kidney-bean-

shaped organshaped organ 4-5 in long, 2-3 in wide,4-5 in long, 2-3 in wide,

1 in thick1 in thick Found just above the waist Found just above the waist

between the peritoneum & between the peritoneum & posterior wall of abdomenposterior wall of abdomen retroperitoneal along with retroperitoneal along with

adrenal glands & uretersadrenal glands & ureters Protected by 11th & 12th Protected by 11th & 12th

ribs with right kidney ribs with right kidney lowerlower

External Anatomy of KidneyExternal Anatomy of Kidney

Blood vessels & ureter enter hilus of kidneyBlood vessels & ureter enter hilus of kidney Renal capsule = transparent membrane maintains organ Renal capsule = transparent membrane maintains organ

shapeshape Adipose capsule that helps protect from trauma Adipose capsule that helps protect from trauma Renal fascia = dense, irregular connective tissue that holds Renal fascia = dense, irregular connective tissue that holds

against back body wallagainst back body wall

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Internal Anatomy of the Internal Anatomy of the KidneysKidneys

Parenchyma of kidneyParenchyma of kidney renal cortex = superficial layer of kidneyrenal cortex = superficial layer of kidney renal medullarenal medulla

inner portion consisting of 8-18 cone-shaped inner portion consisting of 8-18 cone-shaped renal pyramids separated by renal columnsrenal pyramids separated by renal columns

renal papilla point toward center of kidneyrenal papilla point toward center of kidney

Drainage system fills renal sinus cavityDrainage system fills renal sinus cavity cuplike structure (minor calyces) collect cuplike structure (minor calyces) collect

urine from the papillary ducts of the urine from the papillary ducts of the papillapapilla

minor & major calyces empty into the minor & major calyces empty into the renal pelvis which empties into the ureterrenal pelvis which empties into the ureter

Internal Anatomy of KidneyInternal Anatomy of Kidney

What is the difference between renal hilus & renal sinus?What is the difference between renal hilus & renal sinus? Outline a major calyx & the border between cortex & medulla.Outline a major calyx & the border between cortex & medulla.

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Blood & Nerve Supply of Blood & Nerve Supply of KidneyKidney

Abundantly supplied with blood vesselsAbundantly supplied with blood vessels receive 25% of resting cardiac output via receive 25% of resting cardiac output via

renal arteriesrenal arteries Functions of different capillary bedsFunctions of different capillary beds

glomerular capillaries where filtration of glomerular capillaries where filtration of blood occursblood occurs

vasoconstriction & vasodilation of afferent & vasoconstriction & vasodilation of afferent & efferent arterioles produce large changes in efferent arterioles produce large changes in renal filtrationrenal filtration

peritubular capillaries that carry away peritubular capillaries that carry away reabsorbed substances from filtratereabsorbed substances from filtrate

Sympathetic vasomotor nerves regulate Sympathetic vasomotor nerves regulate blood flow & renal resistance by blood flow & renal resistance by altering arteriolesaltering arterioles

Blood Vessels around the Blood Vessels around the NephronNephron

Glomerular capillaries are formed Glomerular capillaries are formed between the afferent & efferent arteriolesbetween the afferent & efferent arterioles

Efferent arterioles give rise to the Efferent arterioles give rise to the peritubular capillaries and vasa rectaperitubular capillaries and vasa recta

Blood Supply to the Blood Supply to the NephronNephron

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The NephronThe Nephron Kidney has over 1 million nephrons composed of Kidney has over 1 million nephrons composed of

a corpuscle and tubulea corpuscle and tubule Renal corpuscle = site of plasma filtrationRenal corpuscle = site of plasma filtration

glomerulus is capillaries where filtration occursglomerulus is capillaries where filtration occurs glomerular (Bowman’s) capsule is double-walled glomerular (Bowman’s) capsule is double-walled

epithelial cup that collects filtrateepithelial cup that collects filtrate Renal tubuleRenal tubule

proximal convoluted tubuleproximal convoluted tubule loop of Henle dips down into medullaloop of Henle dips down into medulla distal convoluted tubuledistal convoluted tubule

Collecting ducts and papillary ducts drain urine to Collecting ducts and papillary ducts drain urine to the renal pelvis and ureterthe renal pelvis and ureter

Cortical NephronCortical Nephron

80-85% of nephrons are cortical nephrons80-85% of nephrons are cortical nephrons Renal corpuscles are in outer cortex and loops Renal corpuscles are in outer cortex and loops

of Henle lie mainly in cortexof Henle lie mainly in cortex

Juxtamedullary NephronJuxtamedullary Nephron

15-20% of nephrons are juxtamedullary nephrons15-20% of nephrons are juxtamedullary nephrons Renal corpuscles close to medulla and long loops of Henle extend Renal corpuscles close to medulla and long loops of Henle extend

into deepest medulla enabling excretion of dilute or concentrated into deepest medulla enabling excretion of dilute or concentrated urineurine

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Histology of the Nephron & Collecting Histology of the Nephron & Collecting DuctDuct

Single layer of Single layer of epithelial cells epithelial cells forms walls of forms walls of entire tubeentire tube

Distinctive features Distinctive features due to function of due to function of each regioneach region microvillimicrovilli cuboidal versus cuboidal versus

simplesimple hormone receptorshormone receptors

Structure of Renal Structure of Renal CorpuscleCorpuscle

Bowman’s capsule surrounds capsular spaceBowman’s capsule surrounds capsular space podocytes cover capillaries to form visceral layerpodocytes cover capillaries to form visceral layer simple squamous cells form parietal layer of capsulesimple squamous cells form parietal layer of capsule

Glomerular capillaries arise from afferent arteriole & Glomerular capillaries arise from afferent arteriole & form a ball before emptying into efferent arterioleform a ball before emptying into efferent arteriole

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Juxtaglomerular ApparatusJuxtaglomerular Apparatus

Structure where afferent arteriole makes Structure where afferent arteriole makes contact with ascending limb of loop of Henlecontact with ascending limb of loop of Henle macula densa is thickened part of ascending limbmacula densa is thickened part of ascending limb juxtaglomerular cells are modified muscle cells in juxtaglomerular cells are modified muscle cells in

arteriolearteriole

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Number of NephronsNumber of Nephrons Remains constant from birthRemains constant from birth

any increase in size of kidney is size increase of any increase in size of kidney is size increase of individual nephronsindividual nephrons

If injured, no replacement occursIf injured, no replacement occurs Dysfunction is not evident until function Dysfunction is not evident until function

declines by 25% of normal (other nephrons declines by 25% of normal (other nephrons handle the extra work)handle the extra work)

Removal of one kidney causes enlargement Removal of one kidney causes enlargement of the remaining until it can filter at 80% of of the remaining until it can filter at 80% of normal rate of 2 kidneysnormal rate of 2 kidneys

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Overview of Renal Overview of Renal PhysiologyPhysiology

Nephrons and collecting ducts perform 3 Nephrons and collecting ducts perform 3 basic processesbasic processes glomerular filtrationglomerular filtration

a portion of the blood plasma is filtered into the a portion of the blood plasma is filtered into the kidneykidney

tubular reabsorptiontubular reabsorption water & useful substances are reabsorbed into the water & useful substances are reabsorbed into the

bloodblood tubular secretiontubular secretion

wastes are removed from the blood & secreted into wastes are removed from the blood & secreted into urineurine

Rate of excretion of any substance is its Rate of excretion of any substance is its rate of filtration, plus its rate of secretion, rate of filtration, plus its rate of secretion, minus its rate of reabsorptionminus its rate of reabsorption

Overview of Renal PhysiologyOverview of Renal Physiology

Glomerular filtration of plasmaGlomerular filtration of plasma Tubular reabsorptionTubular reabsorption Tubular secretionTubular secretion

Glomerular FiltrationGlomerular Filtration Blood pressure produces glomerular filtrateBlood pressure produces glomerular filtrate Filtration fraction is 20% of plasmaFiltration fraction is 20% of plasma 48 Gallons/day48 Gallons/day

filtrate reabsorbedfiltrate reabsorbedto 1-2 qt. urineto 1-2 qt. urine

Filtering capacityFiltering capacityenhanced by:enhanced by: thinness of membrane & large surface area of thinness of membrane & large surface area of

glomerular capillariesglomerular capillaries glomerular capillary BP is high due to small glomerular capillary BP is high due to small

size of efferent arteriolesize of efferent arteriole

Filtration MembraneFiltration Membrane

#1 Stops all cells and platelets#1 Stops all cells and platelets #2 Stops large plasma proteins#2 Stops large plasma proteins #3 Stops medium-sized proteins, not small ones#3 Stops medium-sized proteins, not small ones

Glomerular Filtration RateGlomerular Filtration Rate Amount of filtrate formed in all renal Amount of filtrate formed in all renal

corpuscles of both kidneys / minutecorpuscles of both kidneys / minute average adult male rate is 125 mL/minaverage adult male rate is 125 mL/min

Homeostasis requires GFR that is constantHomeostasis requires GFR that is constant too high & useful substances are lost due to the too high & useful substances are lost due to the

speed of fluid passage through nephronspeed of fluid passage through nephron too low and sufficient waste products may not be too low and sufficient waste products may not be

removed from the bodyremoved from the body Changes in net filtration pressure affects GFRChanges in net filtration pressure affects GFR

filtration stops if GBHP drops to 45mm Hgfiltration stops if GBHP drops to 45mm Hg functions normally with mean arterial pressures 80-functions normally with mean arterial pressures 80-

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Renal Autoregulation of GFRRenal Autoregulation of GFR Mechanisms that maintain a constant GFR Mechanisms that maintain a constant GFR despite changes in arterial BPdespite changes in arterial BP myogenic mechanismmyogenic mechanism

systemic increases in BP, stretch the afferent systemic increases in BP, stretch the afferent arteriolearteriole

smooth muscle contraction reduces the diameter of smooth muscle contraction reduces the diameter of the arteriole returning the GFR to its previous level the arteriole returning the GFR to its previous level in secondsin seconds

tubuloglomerular feedbacktubuloglomerular feedback elevated systemic BP raises the GFR so that fluid elevated systemic BP raises the GFR so that fluid

flows too rapidly through the renal tubule & Na+, flows too rapidly through the renal tubule & Na+, Cl- and water are not reabsorbedCl- and water are not reabsorbed

macula densa detects that difference & releases a macula densa detects that difference & releases a vasoconstrictor from the juxtaglomerular apparatusvasoconstrictor from the juxtaglomerular apparatus

afferent arterioles constrict & reduce GFRafferent arterioles constrict & reduce GFR

Neural Regulation of GFRNeural Regulation of GFR Blood vessels of the kidney are supplied by Blood vessels of the kidney are supplied by

sympathetic fibers that cause vasoconstriction of sympathetic fibers that cause vasoconstriction of afferent arteriolesafferent arterioles

At rest, renal BV are maximally dilated because At rest, renal BV are maximally dilated because sympathetic activity is minimalsympathetic activity is minimal renal autoregulation prevailsrenal autoregulation prevails

With moderate sympathetic stimulation, both With moderate sympathetic stimulation, both afferent & efferent arterioles constrict equallyafferent & efferent arterioles constrict equally decreasing GFR equallydecreasing GFR equally

With extreme sympathetic stimulation (exercise With extreme sympathetic stimulation (exercise or hemorrhage), vasoconstriction of afferent or hemorrhage), vasoconstriction of afferent arterioles reduces GFRarterioles reduces GFR lowers urine output & permits blood flow to other lowers urine output & permits blood flow to other

tissuestissues

Tubular Reabsorption & Tubular Reabsorption & SecretionSecretion

Normal GFR is so high that volume of filtrate Normal GFR is so high that volume of filtrate in capsular space in half an hour is greater in capsular space in half an hour is greater than the total plasma volumethan the total plasma volume

Nephron must reabsorb 99% of the filtrateNephron must reabsorb 99% of the filtrate PCT with their microvilli do most of work with rest PCT with their microvilli do most of work with rest

of nephron doing just the fine-tuning of nephron doing just the fine-tuning solutes reabsorbed by active & passive processessolutes reabsorbed by active & passive processes water follows by osmosiswater follows by osmosis small proteins by pinocytosissmall proteins by pinocytosis

Important function of nephron is tubular Important function of nephron is tubular secretionsecretion transfer of materials from blood into tubular fluidtransfer of materials from blood into tubular fluid

helps control blood pH because of secretion of H+helps control blood pH because of secretion of H+ helps eliminate certain substances (NH4+, creatinine, helps eliminate certain substances (NH4+, creatinine,

K+)K+)

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Transport MechanismsTransport Mechanisms Water is only reabsorbed by osmosisWater is only reabsorbed by osmosis

obligatory water reabsorption occurs obligatory water reabsorption occurs when water is “obliged” to follow the when water is “obliged” to follow the solutes being reabsorbedsolutes being reabsorbed

facultative water reabsorption occurs in facultative water reabsorption occurs in collecting duct under the control of collecting duct under the control of antidiuretic hormoneantidiuretic hormone

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GlucosuriaGlucosuria

Common cause is diabetes mellitis Common cause is diabetes mellitis because insulin activity is deficient because insulin activity is deficient and blood sugar is too highand blood sugar is too high

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Reabsorption in the Loop of Reabsorption in the Loop of HenleHenle

Tubular fluidTubular fluid PCT reabsorbed 65% of the filtered water so PCT reabsorbed 65% of the filtered water so

chemical composition of tubular fluid in the chemical composition of tubular fluid in the loop of Henle is quite different from plasmaloop of Henle is quite different from plasma

since many nutrients were reabsorbed as since many nutrients were reabsorbed as well, osmolarity of tubular fluid is close to that well, osmolarity of tubular fluid is close to that of bloodof blood

Sets the stage for independent regulation Sets the stage for independent regulation of both volume & osmolarity of body fluidsof both volume & osmolarity of body fluids

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Symporters in the Loop of Symporters in the Loop of HenleHenle

Thick limb of loop of Thick limb of loop of Henle has Na+ K- Henle has Na+ K- Cl- symporters that Cl- symporters that reabsorb these ionsreabsorb these ions

K+ leaks through K+ leaks through K+ channels back K+ channels back into the tubular fluid into the tubular fluid leaving the leaving the interstitial fluid and interstitial fluid and blood with a blood with a negative chargenegative charge

Cations passively Cations passively move to the vasa move to the vasa recta recta

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Reabsorption & Secretion in Reabsorption & Secretion in the Collecting Ductthe Collecting Duct

By end of DCT, 95% of solutes & water By end of DCT, 95% of solutes & water have been reabsorbed and returned to have been reabsorbed and returned to the bloodstreamthe bloodstream

Cells in the collecting duct make the Cells in the collecting duct make the final adjustmentsfinal adjustments principal cells reabsorb Na+ and secrete principal cells reabsorb Na+ and secrete

K+K+ intercalated cells reabsorb K+ & intercalated cells reabsorb K+ &

bicarbonate ions and secrete H+bicarbonate ions and secrete H+

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Actions of the Principal CellsActions of the Principal Cells Na+ enters principal cellsNa+ enters principal cellsthrough leakage channelsthrough leakage channels

Na+ pumps keep theNa+ pumps keep theconcentration of Na+ inconcentration of Na+ inthe cytosol lowthe cytosol low

Cells secrete variableCells secrete variableamounts of K+, to adjustamounts of K+, to adjustfor dietary changes in K+for dietary changes in K+intakeintake down concentration gradient due to Na+/K+ down concentration gradient due to Na+/K+

pump pump Aldosterone increases Na+ and water Aldosterone increases Na+ and water

reabsorption & K+ secretion by principal cells reabsorption & K+ secretion by principal cells by stimulating the synthesis of new pumps by stimulating the synthesis of new pumps and channels.and channels.

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Secretion of H+ and Secretion of H+ and Absorption of Bicarbonate by Absorption of Bicarbonate by

Intercalated CellsIntercalated Cells Proton pumps (H+ATPases) Proton pumps (H+ATPases)

secrete H+ into tubular fluidsecrete H+ into tubular fluid can secrete against a can secrete against a

concentration gradient so urine concentration gradient so urine can be 1000 times more acidic can be 1000 times more acidic than bloodthan blood

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Hormonal RegulationHormonal Regulation Hormones that affect Na+, Cl- & Hormones that affect Na+, Cl- &

water reabsorption and K+ secretion water reabsorption and K+ secretion in the tubulesin the tubules angiotensin II and aldosteroneangiotensin II and aldosterone

decreases GFR by vasoconstricting afferent decreases GFR by vasoconstricting afferent arteriolearteriole

enhances absorption of Na+enhances absorption of Na+ promotes aldosterone production which promotes aldosterone production which

causes principal cells to reabsorb more Na+ causes principal cells to reabsorb more Na+ and Cl- and less waterand Cl- and less water

increases blood volume by increasing water increases blood volume by increasing water reabsorptionreabsorption

Antidiuretic HormoneAntidiuretic Hormone Increases water Increases water permeability of principal permeability of principal cellscells

When osmolarity of When osmolarity of plasma & interstitial fluid plasma & interstitial fluid decreases, more ADH is decreases, more ADH is secreted secreted

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Production of Dilute or Production of Dilute or Concentrated UrineConcentrated Urine

Homeostasis of body fluids despite Homeostasis of body fluids despite variable fluid intakevariable fluid intake

Kidneys regulate water loss in urineKidneys regulate water loss in urine ADH controls whether dilute or ADH controls whether dilute or

concentrated urine is formedconcentrated urine is formed if lacking, urine contains high ratio of if lacking, urine contains high ratio of

water to soluteswater to solutes

Formation of Dilute UrineFormation of Dilute Urine Dilute = having fewer Dilute = having fewer

solutes than plasmasolutes than plasma diabetes insipidusdiabetes insipidus

Filtrate and blood have Filtrate and blood have equal osmolarity in PCTequal osmolarity in PCT

Principal cells do not Principal cells do not reabsorb water if ADH is reabsorb water if ADH is lowlow

Formation of Concentrated Formation of Concentrated UrineUrine Compensation for low water intake or heavy Compensation for low water intake or heavy

perspirationperspiration Urine can be up to 4 times greater osmolarity Urine can be up to 4 times greater osmolarity

than plasmathan plasma Cells in the collecting ducts reabsorb more Cells in the collecting ducts reabsorb more

water & urea when ADH is increasedwater & urea when ADH is increased

SummarSummaryy

H2O Reabsorption H2O Reabsorption PCT---65%PCT---65% loop---15%loop---15% DCT----10-15%DCT----10-15% collecting duct--- collecting duct---

5-10% with ADH5-10% with ADH Dilute urine has not Dilute urine has not

had enough water had enough water removed, although removed, although sufficient ions have sufficient ions have been reabsorbed.been reabsorbed.

Reabsorption within Loop of Reabsorption within Loop of HenleHenle

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DiureticsDiuretics

Substances that slow renal Substances that slow renal reabsorption of water & cause reabsorption of water & cause diuresis (increased urine flow rate)diuresis (increased urine flow rate) caffeine which inhibits Na+ caffeine which inhibits Na+

reabsorptionreabsorption alcohol which inhibits secretion of ADHalcohol which inhibits secretion of ADH prescription medicines can act on the prescription medicines can act on the

PCT, loop of Henle or DCTPCT, loop of Henle or DCT

Evaluation of Kidney Evaluation of Kidney FunctionFunction UrinalysisUrinalysis

analysis of the volume and properties of urineanalysis of the volume and properties of urine normal urine is protein free, but includes filtered & normal urine is protein free, but includes filtered &

secreted electrolytessecreted electrolytes urea, creatinine, uric acid, urobilinogen, fatty acids, urea, creatinine, uric acid, urobilinogen, fatty acids,

enzymes & hormonesenzymes & hormones

Blood testsBlood tests blood urea nitrogen test (BUN) measures urea in blood urea nitrogen test (BUN) measures urea in

bloodblood rises steeply if GFR decreases severelyrises steeply if GFR decreases severely

plasma creatinine--from skeletal muscle plasma creatinine--from skeletal muscle breakdownbreakdown

renal plasma clearance of substance from the renal plasma clearance of substance from the blood in ml/minute (important in drug dosages)blood in ml/minute (important in drug dosages)

Dialysis TherapyDialysis Therapy

Kidney function is so impaired the Kidney function is so impaired the blood must be cleansed artificiallyblood must be cleansed artificially separation of large solutes from smaller separation of large solutes from smaller

ones by a selectively permeable ones by a selectively permeable membranemembrane

Artificial kidney machine performs Artificial kidney machine performs hemodialysishemodialysis directly filters blood because blood flows directly filters blood because blood flows

through tubing surrounded by dialysis through tubing surrounded by dialysis solutionsolution

cleansed blood flows back into the bodycleansed blood flows back into the body

Anatomy of UretersAnatomy of Ureters 10 to 12 in long10 to 12 in long Varies in diameter from 1-10 Varies in diameter from 1-10

mmmm Extends from renal pelvis to Extends from renal pelvis to

bladderbladder RetroperitonealRetroperitoneal Enters posterior wall of bladderEnters posterior wall of bladder Physiological valve onlyPhysiological valve only

bladder wall compresses arterial bladder wall compresses arterial opening as it expands during opening as it expands during fillingfilling

flow results from peristalsis, flow results from peristalsis, gravity & hydrostatic pressuregravity & hydrostatic pressure

Histology of UretersHistology of Ureters

3 layers in wall3 layers in wall mucosa is transitional epithelium & lamina mucosa is transitional epithelium & lamina

propriapropria since organ must inflate & deflatesince organ must inflate & deflate mucus prevents the cells from being contacted by mucus prevents the cells from being contacted by

urineurine muscularismuscularis

inner longitudinal & outer circular smooth muscle inner longitudinal & outer circular smooth muscle layerlayer

distal 1/3 has additional longitudinal layerdistal 1/3 has additional longitudinal layer peristalsis contributes to urine flowperistalsis contributes to urine flow

Location of Urinary BladderLocation of Urinary Bladder

Posterior to pubic symphysisPosterior to pubic symphysis In females is anterior to vagina & inferior to uterusIn females is anterior to vagina & inferior to uterus In males lies anterior to rectumIn males lies anterior to rectum

Anatomy of Urinary Anatomy of Urinary BladderBladder

Hollow, distensible muscular organ with capacity of 700 Hollow, distensible muscular organ with capacity of 700 - 800 mL- 800 mL

Trigone is smooth flat area bordered by 2 ureteral Trigone is smooth flat area bordered by 2 ureteral openings and one urethral openingopenings and one urethral opening

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Histology of Urinary Histology of Urinary BladderBladder

3 layers in wall3 layers in wall mucosa is transitional epithelium & lamina propriamucosa is transitional epithelium & lamina propria

since organ must inflate & deflatesince organ must inflate & deflate mucus prevents the cells from being contacted by urinemucus prevents the cells from being contacted by urine

muscularis (known as detrusor muscle)muscularis (known as detrusor muscle) 3 layers of smooth muscle 3 layers of smooth muscle

inner longitudinal, middle circular & outer longitudinalinner longitudinal, middle circular & outer longitudinal circular smooth muscle fibers form internal urethral circular smooth muscle fibers form internal urethral

sphinctersphincter circular skeletal muscle forms external urethral circular skeletal muscle forms external urethral

sphinctersphincter adventitia layer of loose connective tissue adventitia layer of loose connective tissue

anchors in placeanchors in place superior surface has serosal layer (visceral peritoneum)superior surface has serosal layer (visceral peritoneum)

Micturition ReflexMicturition Reflex Micturition or urination (voiding)Micturition or urination (voiding) Stretch receptors signal spinal cord and brainStretch receptors signal spinal cord and brain

when volume exceeds 200-400 mLwhen volume exceeds 200-400 mL Impulses sent to micturition center in sacral spinal Impulses sent to micturition center in sacral spinal

cord (S2 and S3) & reflex is triggeredcord (S2 and S3) & reflex is triggered parasympathetic fibers cause detrusor muscle to parasympathetic fibers cause detrusor muscle to

contract, external & internal sphincter muscles to relaxcontract, external & internal sphincter muscles to relax Filling causes a sensation of fullness that initiates Filling causes a sensation of fullness that initiates

a desire to urinate before the reflex actually a desire to urinate before the reflex actually occursoccurs conscious control of external sphincterconscious control of external sphincter cerebral cortex can initiate micturition or delay its cerebral cortex can initiate micturition or delay its

occurrence for a limited period of timeoccurrence for a limited period of time

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Anatomy of the UrethraAnatomy of the Urethra FemalesFemales length of 1.5 in., orifice between clitoris & length of 1.5 in., orifice between clitoris &

vaginavagina histologyhistology

transitional changing to nonkeratinized stratified transitional changing to nonkeratinized stratified squamous epithelium, lamina propria with elastic squamous epithelium, lamina propria with elastic fibers & circular smooth musclefibers & circular smooth muscle

MalesMales tube passes through prostate, UG diaphragm & tube passes through prostate, UG diaphragm &

penispenis 3 regions of urethra3 regions of urethra

prostatic urethra, membranous urethra & spongy prostatic urethra, membranous urethra & spongy urethraurethra

circular smooth muscle forms internal urethral circular smooth muscle forms internal urethral sphincter & UG diaphragm forms external urethral sphincter & UG diaphragm forms external urethral sphinctersphincter

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Urinary IncontinenceUrinary Incontinence Lack of voluntary control over micturitionLack of voluntary control over micturition

normal in 2 or 3 year olds because neurons to normal in 2 or 3 year olds because neurons to sphincter muscle is not developedsphincter muscle is not developed

Stress incontinence in adultsStress incontinence in adults caused by increases in abdominal pressure that caused by increases in abdominal pressure that

result in leaking of urine from the bladderresult in leaking of urine from the bladder coughing, sneezing, laughing, exercising, walkingcoughing, sneezing, laughing, exercising, walking

injury to the nerves, loss of bladder flexibility, injury to the nerves, loss of bladder flexibility, or damage to the sphincteror damage to the sphincter

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Aging and the Urinary Aging and the Urinary SystemSystem Anatomical changesAnatomical changes

kidneys shrink in size from 260 g to 200 gkidneys shrink in size from 260 g to 200 g Functional changesFunctional changes

lowered blood flow & filter less blood (50%) lowered blood flow & filter less blood (50%) diminished sensation of thirst increases diminished sensation of thirst increases

susceptibility to dehydrationsusceptibility to dehydration Diseases common with ageDiseases common with age

acute and chronic inflammations & canaliculiacute and chronic inflammations & canaliculi infections, nocturia, polyuria, dysuria, infections, nocturia, polyuria, dysuria,

retention or incontinence and hematuriaretention or incontinence and hematuria Cancer of prostate is common in elderly Cancer of prostate is common in elderly

menmen

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Disorders of Urinary Disorders of Urinary SystemSystem

Renal calculiRenal calculi Urinary tract infectionsUrinary tract infections Glomerular diseaseGlomerular disease Renal failureRenal failure Polycystic kidney diseasePolycystic kidney disease