Forma&on of Concentrated Urine · •Concentrated urine has a deeper yellow color •Drugs,...

Chapter 25: Urinary System

Forma&onofConcentratedUrine• An#diure#chormone(ADH)inhibitsdiuresis

• DCTandcollec#ngductbecomepermeabletowater

• Thisequalizestheosmolarityofthefiltrateandtheinters##alfluid

• Risesfrom300mOsmto1200mOsmasurinemovethroughmedulla

• InthepresenceofADH,99%ofthewaterinfiltrateisreabsorbed

Forma&onofConcentratedUrine

• ADH‐dependentwaterreabsorp#on

• Calledfaculta#vewaterreabsorp#on

• ADHisthesignaltoproduceconcentratedurine

• Thekidneys’abilitytoresponddependsuponthehighmedullaryosmo#cgradient

• Ifbloodplasmarisesabove300mOsm

• ADHwillbereleasedtodilute

Chapter 25: Urinary System

Forma&onofDiluteandConcentratedUrine

Figure 25.15a, b

RenalClearance

• Thevolumeofplasmathatisclearedofapar#cularsubstanceinoneminute

• Inulin

• Standardforcomparisonwhichiscompletelyremoved(completerenalclearance)

• Plantpolysaccharide

• Renalclearancetestsareusedto:

• DeterminetheGFR

• Detectglomerulardamage

• Followtheprogressofdiagnosedrenaldisease

Chapter 25: Urinary System

RenalClearance

RC=UV/P

RC=renalclearancerate

U=concentra#on(mg/ml)ofthesubstanceinurine

V=flowrateofurineforma#on(ml/min)

P=concentra#onofthesamesubstanceinplasma

• Iflessthaninulin‐somecleared,par#allyreabsorbed

• Ifzero‐nonecleared,allreabsorbed

• Ifgreaterthaninulin‐allcleared,nonereabsorbed

PhysicalCharacteris&csofUrine• Colorandtransparency

• Clear,paletodeepyellow(amber‐duetourochrome)

• Concentratedurinehasadeeperyellowcolor

• Drugs,vitaminsupplements,anddietcanchangethecolorofurine

• Cloudyurinemayindicateinfec#onoftheurinarytract

• OrbacteriaifleYstanding

Chapter 25: Urinary System

PhysicalCharacteris&csofUrine• Odor

• Freshurineisslightlyaroma#c

• Standingurinedevelopsanammoniaodor

• NH4⇒NH3

• Somedrugsandvegetables(asparagus)altertheusualodor

• 40‐50%ofpopula#onmakeasparaguspee!

• Singleautosomaldominantgeneproductcatalyzesasparagustothioesters

• Smaller%unabletosmellit!

• Fruity/sweet

• Diabetesmellitus

PhysicalCharacteris&csofUrine

• pH

• Slightlyacidic(pH6)witharangeof4.5to8.0

• DietcanalterpH

• Moreprotein=moreacidic

• Morevegetables=morealkaline

• Specificgravity

• Rangesfrom1.001to1.035

• Isdependentonsoluteconcentra#on

Chapter 25: Urinary System

ChemicalComposi&onofUrine

• Urineis95%waterand5%solutes

• Urea‐Deamina#onofproteins

• Uricacid‐Catabolismofnucleicacids

• Crea#nine‐Metaboliteofcrea#nefrommuscle#ssue

• Othernormalsolutesinclude:

• Sodium,potassium,phosphate,andsulfateions

• Calcium,magnesium,andbicarbonateions

• Abnormallyhighconcentra#onsofanyurinarycons#tuentsmayindicatepathology

Ureters

• Slendertubesthatconveyurinefromthekidneystothebladder

• Moveretroperitonealatpelviccavity

• Uretersenterthebaseofthebladderthroughtheposteriorwall

• Preventsbackflowofurineintotheureters

Chapter 25: Urinary System

Ureters• Uretershaveatrilayeredwall

• Transi#onalepithelialmucosa

• Smoothmusclemuscularis

• Innerlongitudinal,outercircular

• Peristal#ccontrac#ons

• Fibrousconnec#ve#ssueadven##a

• Uretersac#velypropelurinetothebladderviaresponsetosmoothmusclestretch

UrinaryBladder

• Smooth,collapsible,muscularsac

• Temporarilystoresurine

• Retroperitonealonthepelvicfloor

• Posteriortothepubicsymphysis

• Trigone–triangularareaoutlinedbytheopeningsfortheuretersandtheurethra

• Clinicallyimportantbecauseinfec#onstendtopersistinthisregion

Chapter 25: Urinary System

UrinaryBladder

• Thebladderwallhasthreelayers

• Transi#onalepithelialmucosa

• Triplemuscularlayer‐detrusormuscle

• Innerandouterlongitudinal

• Middlecircular

• Afibrousadven##a

• Thebladderisdistensibleandcollapseswhenempty

• Asurineaccumulates,thebladderexpandswithoutsignificantriseininternalpressure

UrinaryBladder

Figure 25.18a, b

Chapter 25: Urinary System

Urethra

• Thinwalledmusculartube

• Drainsurinefromthebladder

• Mucosa

• Transi#onalepitheliumnearbladder

• Pseudostra#fiedcolumnarinmiddleregion

• Stra#fiedsquamousnearexit

Urethra• Sphincterskeeptheurethraclosedwhenurineisnotbeingpassed

• Internalurethralsphincter–involuntarysphincteratthebladder‐urethrajunc#on

• Smoothmuscle

• Externalurethralsphincter–voluntarysphincter

• Surroundsurethraasitpassesthroughtheurogenitaldiaphragm

• Skeletalmuscleofpelvicfloor

• Levatoranimuscle–voluntaryurethralsphincter

Chapter 25: Urinary System

Urethra• Femaleurethrais#ghtlyboundtotheanteriorvaginalwall

• Posteriortopubicsymphysis

• 1.5”long

• Externalopeninganteriortothevaginalopeningandposteriortotheclitoris

• Maleurethra(~8”)hasthreenamedregions

• Prosta#curethra–runswithintheprostategland

• Membranousurethra–runsthroughtheurogenitaldiaphragm

• Spongy(penile)urethra–passesthroughthepenisandopensviatheexternalurethralorifice

• Conduc#onofurineandsemen

Urethra

Figure 25.18a. b

Chapter 25: Urinary System

Micturi&on(VoidingorUrina&on)• Theactofemptyingthebladder

• Distension⇒stretch/mechanoreceptors⇒reflexarc⇒sacralspinalcord⇒brain⇒inhibitoryors#mulatoryresponse

• S#mulatory

• Efferentparasympathe#cpelvicnervestocontractdetrusormuscleandrelaxinternalurethralsphincter⇒urinemovespastIUS⇒externalurethralsphinctervoluntarilyrelaxed⇒urina#on

• Inhibitory

• Efferentsympathe#cnervesrelaxdetrusormuscle⇒contractIUS⇒stopsurine⇒EUSremainsclosed⇒nourina#on

Micturi&on(VoidingorUrina&on)

Figure 25.20a, b

Chapter 25: Urinary System

Micturi&on(VoidingorUrina&on)

• Incon#nence

• Lackofvoluntarycontroloverurina#on

• Normalininfants

• Olderchildrenoradults

• Ususuallyduetoemo#onalornervoussystemproblems

• Retension

• Inabilitytovoidurine

• Duetoobstruc#oninurethraorbladder

• UTI’s,prosta##s,prostatecancer