RENAL PHYSIOLOGY.ppt

Renal Physiology, Nephron, Glomerular Filtration, Formation of Urine, Concentration of Urine, Diuretics

1. By
Dr. Faraza Javaid

2. INTRODUCTION
Excretionistheprocessbywhichtheunwanted
substances and metabolic wastes are
eliminatedfromthebody.
1.Digestivesystemexcretesfoodresiduesin
theformoffeces.Somebacteriaandtoxic
substancesalsoareexcretedthroughfeces
2.Lungsremovecarbondioxideandwatervapor
3.Skinexcreteswater,saltsandsomewastes.
Italsoremovesheatfromthebody
4.Liverexcretesmanysubstances likebile
pigments,heavymetals,drugs,toxins,bacteria,
etc.throughbile.

3. FUNCTIONS OF KIDNEY
Excretion of Waste Products
Maintenance of Water Balance
Maintenance of Electrolyte Balance
Maintenance of Acid–Base Balance
Hemopoietic Function
Regulation of Blood Calcium Level

4. KIDNEY
Two kidneys inallmammals located
retroperitoneallyattheleveloflowerribs
Protectedbythe11
th
and12
th
ribsfromthe
injury
Leftoneisabitontheanteriorsideas
comparedtotheright
Outerdarkerregioniscortex,Innerlighter
regionisthemedullawithCalyces(majorand
minor),Renalpyramids,Renalpelvisand
Bloodvessels

6. NEPHRONS
Nephronisthestructuralandfunctional
unitofthekidney
2,400,000nephronscollectivelyinboth
kidneys
Basicallycomposedof:
Renalcorpuscle(inwhishfluidisfiltered)
Alongtubule(convertsthefiltrateinto
urineonitswaytotherenalpelvis)

7. TYPES OF NEPHRON
1.Corticalnephronsorsuperficialnephrons:
Nephronshavingthecorpusclesinoutercortex
ofthekidneyneartheperiphery.Inhuman
kidneys,85%nephronsarecorticalnephrons.
2.Juxtamedullary nephrons:Nephronshaving
thecorpusclesininnercortexnearmedullaor
corticomedullaryjunction.

8. STRUCTURE OF NEPHRON
Bowman’s Capsule
Proximal convoluted
tubule
Loop of Henle
(descending limb and
ascending limb)
Distal convoluted
tubule
Collecting tubule
Collecting duct

10. RENAL CORPUSCLE
Glomerulus
Glomerulus isatuftofcapillariesenclosedby
Bowman capsule.Itconsists ofglomerular
capillariesinterposedbetweenafferentarterioleon
oneendandefferentarterioleontheotherend.
Thus,thevascularsystemintheglomerulusis
purelyarterial.
Bowman Capsule
Bowman capsuleisacapsularstructure,which
enclosestheglomerulus.Itisformedbytwolayers:
i.Innerviscerallayer,ii.Outerparietallayer.
FunctionalanatomyofBowman capsuleresembles
afunnelwithfilterpaper.

11. TUBULAR PORTION OF NEPHRON
PROXIMAL CONVOLUTED TUBULE
Proximalconvolutedtubuleisthecoiledportion
arisingfromBowman capsule.Itissituatedinthe
cortex.Itiscontinuedasdescendinglimbofloopof
Henle.Lengthofproximalconvolutedtubuleis14
mmandthediameteris55μ.
LOOPOFHENLE
LoopofHenleconsistsof:
i.Descendinglimb
ii.Hairpinbend
iii.Ascendinglimb.

12. DescendingLimb
DescendinglimbofloopofHenleismadeupoftwo
segments:
Thick descending segment isthe direct
continuationoftheproximalconvolutedtubule.It
descendsdownintomedulla.Ithasalengthof6
mmandadiameterof55μ.
Thickdescending segment iscontinuedasthin
descendingsegment.Itiscontinuedashairpinbend
oftheloop.
HairpinBend
Hairpinbendformedbyflattenedepithelialcells
withoutbrushborderanditiscontinuedasthe
ascendinglimbofloopofHenle.

13. AscendingLimb
AscendinglimborsegmentofHenleloophastwo
parts:
Thinascending segment iscontinuedasthick
ascendingsegment.
Thickascendingsegmentisabout9mmlongwitha
diameterof30μ.Theterminalportionofthick
ascending segment, whichrunsbetween the
afferentandefferentarteriolesofthesame
nephronsformsthemaculadensa.Maculadensais
thepartofjuxtaglomerular apparatus.Thick
ascending segment ascendstothecortexand
continuesasdistalconvolutedtubule.

14. Length and the extent of the loop of Henle vary
in different nephrons:
In cortical nephrons, it is short and the hairpin
bend penetrates only up to outer medulla.
In juxtamedullary nephrons , this is long and the
hairpin bend extends deep into the inner
medulla.

15. DISTALCONVOLUTED TUBULE
Distalconvolutedtubuleisthecontinuationof
thickascendingsegmentandoccupiesthecortex
ofkidney.Itiscontinuedascollectingduct.The
lengthofthedistalconvolutedtubuleis14.5to15
mm.Ithasadiameterof22to50μ.
COLLECTING DUCT
Collectingductisformedbytwotypesof
epithelialcells:1.PrincipalorPcells,2.
IntercalatedorIcells.Distalconvolutedtubule
continuesastheinitialorarchedcollectingduct,
whichisincortex.Thelowerpartofthe
collectingductliesinmedulla.Seventoteninitial
collectingductsunitetoformthestraight
collectingduct,whichpassesthroughmedulla.

16. Renal Circulation

17. Peritubular
Veins

19. REGULATION OF RENAL BLOOD
FLOW
RenalAutoregulation
Renalautoregulationisimportanttomaintain
theglomerularfiltrationrate(GFR).Bloodflow
tokidneysremainsnormalevenwhenthe
mean arterialbloodpressurevarywidely
between60mmHgand180mmHg.Thishelps
tomaintainnormalGFR.
Two mechanisms areinvolvedinrenal
autoregulation:
1.Myogenicresponse
2.Tubulo-glomerularfeedback

20. Regulationofbloodpressure by renin-angiotensin

21. SECRETION OF HORMONES
Juxtaglomerular apparatus secretes two
hormones:
1. Renin
2. Prostaglandin

22. 1. Renin
Juxtaglomerular cellssecreterenin.Reninisa
peptidewith340amino acids.Alongwith
angiotensins,reninformstherenin-angiotensin
system,whichisahormonesystemthatplaysan
importantroleinthemaintenance ofblood
pressure.
Stimulantsforreninsecretion
Secretionofreninisstimulatedbyfourfactors:
i.Fallinarterialbloodpressure
ii.ReductionintheECFvolume
iii.Increasedsympatheticactivity
iv.Decreased loadofsodiumandchloridein
maculadensa.

23. Actions of Angiotensins
AngiotensinIisphysiologicallyinactiveand
servesonlyastheprecursorofangiotensinII.
AngiotensinIIisthemostactiveform.Its
actionsare:
Angiotensin IIincreases arterialblood
pressurebydirectlyactingontheblood
vesselsandcausingvasoconstriction.Itisa
potentconstrictorofarterioles.
Itincreasesbloodpressureindirectlyby
increasingthereleaseofnoradrenalinefrom
postganglionic sympathetic fibers.
Noradrenalineisageneralvasoconstrictor.

26. INTRODUCTION
Urineformation isabloodcleansing
function.Kidneysexcretetheunwanted
substancesalongwithwaterfromtheblood
asurine.Normalurinaryoutputis1L/dayto
1.5L/day.
A.Glomerularfiltration
B.Tubularreabsorption
C.Tubularsecretion

29. GLOMERULAR FILTRATION
Glomerularfiltrationistheprocessby
whichthebloodisfilteredwhilepassing
throughtheglomerular capillariesby
filtrationmembrane.
Itisthefirstprocessofurineformation.
Thestructureoffiltrationmembrane is
wellsuitedforfiltration.

30. Filtration Membrane
Filtration membrane is formed by three
layers:
1. Glomerular capillary membrane
(Single layer, Pores/Fenestre/Filtration pore)
2. Basement membrane
(Basement membrane separates the
endotheliumofglomerularcapillaryandlayer
ofBowman capsule)
3. Visceral layer of Bowman capsule
(Single layer, Podocytes, Slit pores)

31. Ultrafiltration
Glomerular filtration is called
ultrafiltrationbecauseeventheminute
particlesarefiltered.
But,theplasmaproteinsarenotfiltered
duetotheirlargemolecularsize.The
proteinmoleculesarelargerthantheslit
porespresentintheendothelium of
capillaries.
Thus,theglomerularfiltratecontainsall
thesubstancespresentinplasmaexcept
theplasmaproteins.

32. GLOMERULAR FILTRATION RATE
Glomerularfiltrationrate(GFR)isdefinedas
thetotalquantityoffiltrateformedinallthe
nephronsofboththekidneysinthegiven
unitoftime.
NormalGFRis125mL/minuteorabout180
L/day.

33. FILTRATION FRACTION
Filtrationfractionisthefraction(portion)ofthe
renalplasma,whichbecomesthefiltrate.Itis
theratiobetween renalplasmaflowand
glomerularfiltrationrate.Itisexpressedin
percentage.

34. PRESSURES DETERMINING
FILTRATION
Pressures,whichdeterminetheGFRare:
1.Glomerularcapillarypressure
2.Colloidalosmoticpressureinthe
glomeruli
3.HydrostaticpressureintheBowman
capsule

35. Net Filtration Pressure
Netfiltrationpressureisthebalancebetween
pressure favoringfiltrationandpressures
opposingfiltration.Itisotherwiseknownas
effectivefiltrationpressure oressential
filtrationpressure.

36. Starling Hypothesis
Starlinghypothesisstatesthatthenet
filtrationthroughcapillarymembrane is
proportionaltohydrostaticpressure
differenceacrossthemembrane minus
oncoticpressuredifference.

37. FACTORS REGULATING GFR
1. Renal Blood Flow
2. Tubulo-glomerular Feedback
3. Glomerular Capillary Pressure
4. Colloidal Osmotic Pressure
5. Hydrostatic Pressure in Bowman Capsule
6. Constriction of Afferent Arteriole
7. Constriction of Efferent Arteriole
8. Systemic Arterial Pressure
9. Sympathetic Stimulation
10. Surface Area of Capillary Membrane
11. Permeability of Capillary Membrane
12. Hormonal and Other Factors

39. INTRODUCTION
Tubularreabsorptionistheprocessby
whichwaterandothersubstancesare
transportedfromrenaltubulesbackto
theblood.
Largequantityofwater(morethan
99%), electrolytes and other
substances arereabsorbed bythe
tubularepithelialcells.

40. ROUTES OF REABSORPTION
Reabsorptionofsubstancesfromtubular
lumenintotheperitubularcapillary
occursbytworoutes:
1.Transcelluarroute
2.Paracellularroute

42. SITE OF REABSORPTION
1.SubstancesReabsorbedfromProximalConvoluted
Tubule
Substances reabsorbedfromproximalconvoluted
tubuleareglucose,aminoacids,sodium,potassium,
calcium,bicarbonates,chlorides,phosphates,urea,
uricacidandwater.
2.SubstancesReabsorbedfromLoopofHenle
Substances reabsorbed fromloopofHenleare
sodiumandchloride.
3.Substances Reabsorbed fromDistalConvoluted
Tubule
Sodium, calcium,bicarbonate andwaterare
reabsorbedfromdistalconvolutedtubule.

43. REGULATION OF TUBULAR
REABSORPTION
Tubular reabsorption is regulated by
three factors:
1. Glomerulo-tubular balance
2. Hormonal factors
3. Nervous factors

46. INTRODUCTION
Tubularsecretionistheprocessbywhichthe
substances aretransportedfrombloodinto
renaltubules.Itisalsocalledtubularexcretion.
Such substances are:
1. Paraaminohippuric acid (PAH)
2. Diodrast
3. 5-hydroxyindoleacetic acid (5HIAA)
4. Amino derivatives
5. Penicillin

47. SUMMARY OF URINE FORMATION
1.Glomerularfiltration
Plasma isfilteredinglomeruliandthe
substancesreachtherenaltubulesalongwith
waterasfiltrate.
2.TubularReabsorption
The99%offiltrateisreabsorbedindifferent
segmentsofrenaltubules.
3.TubularSecretion
Somesubstancesaretransportedfromblood
intotherenaltubule.

49. INTRODUCTION
Everyday180Lofglomerularfiltrateisformed
withlargequantityofwater.Osmolarityof
glomerularfiltrateissameasthatofplasma
anditis300mOsm/L.But,normallyurineis
concentratedanditsosmolarityisfourtimes
morethanthatofplasma,i.e.1,200mOsm/L.
Osmolarityofurinedependsupontwofactors:
1.Watercontentinthebody
2.Antidiuretichormone(ADH)

50. FORMATION OF DILUTE URINE
When,watercontentinthebodyincreases,
kidneyexcretesdiluteurine.
Thisisachieved byinhibitionofADH
secretionfromposteriorpituitary.
Sowaterreabsorptionfromrenaltubulesdoes
nottakeplaceleadingtoexcretionoflarge
amountofwater.Thismakestheurinedilute.

51. FORMATION OF CONCENTRATED
URINE
Whenthewatercontentinbodydecreases,
kidney retains water and excretes
concentrated urine. Formation of
concentratedurineisnotassimpleasthat
ofdiluteurine.
Itinvolvestwoprocesses:
1.Development andmaintenance of
medullary gradient bycountercurrent
system
2.SecretionofADH

52. MEDULLARY GRADIENT
Divisions of Countercurrent System
Countercurrent system has two
divisions:
1.Countercurrent multiplierformedby
loopofHenle
2.Countercurrentexchangerformedby
vasarecta

53. ADH

54. ROLE OF ADH
Finalconcentrationofurineisachievedby
theactionofADH.
Normally,thedistalconvolutedtubuleand
collectingductarenotpermeable to
water.
ButthepresenceofADHmakesthem
permeable, resulting in water
reabsorption.
WaterreabsorptioninducedbyADHis
calledfacultativereabsorptionofwater

55. SUMMARY OF URINE
CONCENTRATION
1.BOWMAN CAPSULE
GlomerularfiltratecollectedattheBowman
capsuleisisotonictoplasma.Thisisbecauseit
containsallthesubstancesofplasmaexcept
proteins.
OsmolarityofthefiltrateatBowman capsuleis
300mOsm/L.

56. 2.PROXIMAL CONVOLUTED TUBULE
When thefiltrateflowsthroughproximal
convolutedtubule,thereisactivereabsorption
ofsodiumandchloridefollowedbyobligatory
reabsorptionofwater.

57. 3.THICKDESCENDING SEGMENT
Waterisreabsorbed fromtubuleintoouter
medullaryinterstitiumbymeansofosmosis.It
isduetotheincreasedosmolarityinthe
medullaryinterstitium,i.e.outsidethethick
descendingtubule.
Theosmolarityofthefluidinsidethissegment
isbetween450and600mOsm/L.Thatmeans
thefluidisslightlyhypertonictoplasma.

58. 4.THINDESCENDING SEGMENT OF
HENLELOOP
Intheshortloopsofcorticalnephrons,the
osmolarityoffluidatthehairpinbendofloop
becomes600mOsm/L.And,inthelongloopsof
juxtamedullarynephrons,atthehairpinbend,
theosmolarityis1,200mOsm/L.Thusinthis
segmentthefluidishypertonictoplasma.

59. 5.THIN ASCENDING SEGMENT OF
HENLELOOP
Whenthethinascendingsegmentoftheloop
ascendsupwardsthroughthemedullaryregion,
osmolarity decreases gradually.Due to
concentration gradient, sodium chloride
diffusesoutoftubularfluidandosmolarity
decreasesto400mOsm/L.Thefluidinthis
segmentisslightlyhypertonictoplasma.

60. 6.THICKASCENDING SEGMENT
Thissegment isimpermeable towater.But
thereisactivereabsorptionofsodiumand
chloridefromthis.Reabsorption ofsodium
decreasestheosmolarityoftubularfluidtoa
greaterextent.Theosmolarityisbetween150
and200mOsm/L.Thefluidinsidebecomes
hypotonictoplasma.

61. 7.DISTALCONVOLUTED TUBULE AND
COLLECTING DUCT
Inthepresence ofADH,distalconvoluted
tubuleandcollectingductbecomepermeable
towaterresultinginwaterreabsorptionand
finalconcentrationofurine.Itisfoundthatin
thecollectingduct,Principal(P)cellsare
responsible for ADH induced water
reabsorption.Reabsorptionoflargequantityof
waterincreases theosmolarity to1,200
mOsm/L.Theurinebecomes hypertonicto
plasma.

63. INTRODUCTION
Micturitionisaprocessbywhichurineis
voidedfromtheurinarybladder.Itisareflex
process.However,ingrownupchildrenand
adults,itcanbecontrolledvoluntarilytosome
extent.

64. URINARY BLADDER & URETHRA
Urinarybladderisatriangularholloworgan
locatedinlowerabdomen.Itconsistsofabody
andneck.Wallofthebladderisformedby
smoothmuscle.Itconsistsofthreeill-defined
layersofmusclefiberscalleddetrusormuscle,
viz.theinnerlongitudinallayer,middlecircular
layerandouterlongitudinallayer.Bladderis
openedinurethrafromwhereurineisexcreted
outfromthebody.

65. URETHRAL SPHINCTERS
Therearetwourethralsphinctersin
urinarytract:
1.Internalurethralsphincter
2.Externalurethralsphincter.

66. NERVE SUPPLY TO URINARY
BLADDER AND SPHINCTERS

67. MICTURITION REFLEX

70. PROPERTIES OF URINE
Volume : 1,000 to 1,500 mL/day
Reaction : Slightly acidic with pH of 4.5 to 6
Specific gravity : 1.010 to 1.025
Osmolarity : 1,200 mOsm/L
Color : Normally, straw colored
Odor : Fresh urine has light aromatic odor.

71. COMPOSITION OF URINE

72. EXAMINATION OF URINE –URINEANALYSIS
Urine analysis is done by:
i. Physical examination
ii. Microscopic examination
iii. Chemical analysis

74. INTRODUCTION
Renalfailurereferstofailureofexcretoryfunctions
ofkidney.Itisusually,characterizedbydecreasein
glomerular filtrationrate(GFR).SoGFR is
consideredasthebestindexofrenalfailure.Renal
failureisalways accompanied by other
complicationssuchas:
1.Deficiencyofcalcitriol(activatedvitaminD)
resultinginreductionofcalciumabsorptionfrom
intestineandhypocalcemia
2.Deficiencyoferythropoietinresultinginanemia
3.Disturbancesinacidbasebalance.

75. ACUTE RENAL FAILURE
Acuterenalfailureistheabruptorsudden
stoppageofrenalfunctions.
Itisoftenreversiblewithinfewdaystofew
weeks.
Acuterenalfailuremayresultinsuddenlife-
threateningreactionsinthebodywiththe
needforemergencytreatment.

76. CAUSES
1. Acute nephritis
2. Damage of renal tissues by poisons like lead,
mercury
3.Renalischemia,whichdevelopsduring
circulatoryshock
4. Acute tubular necrosis
5. Severe transfusion reactions
6.Sudden fallinbloodpressure during
hemorrhage,diarrhea,severeburnsandcholera
7.Blockageofureterduetotheformationof
calculi(renalstone)ortumor.

77. FEATURES
1.Oliguria(decreasedurinaryoutput)
2.Anuria(cessationofurineformation)inseverecases
3.Proteinuria(appearanceofproteinsinurine)including
albuminuria(excretionofalbumininurine)
4.Hematuria(presenceofbloodinurine)
5.Edemaduetoincreasedvolumeofextracellularfluid
(ECF)causedbyretentionofsodiumandwater
6.Hypertensionwithinfewdaysbecauseofincreased
ECFvolume
7.Acidosisduetotheretentionofmetabolicend
products
8.Comaduetosevereacidosis(ifthepatientisnot
treatedintime)resultingindeathwithin10to14days.

78. CHRONIC RENAL FAILURE
CAUSES
1. Chronic nephritis
2. Polycystic kidney disease
3. Renal calculi (kidney stones)
4. Urethral constriction
5. Hypertension
6. Atherosclerosis
7. Tuberculosis
8. Slow poisoning by drugs or metals.

80. INTRODUCTION
Diuretics ordiureticagents arethe
substances which enhance theurine
formationandoutput.
Thesesubstancesincreasetheexcretionof
water,sodiumandchloridethroughurine.
Diureticagentsincreasetheurineformation,
byinfluencinganyoftheprocessesinvolved
inurineformation.
Diureticsarecommonlycalled‘waterpills’.

81. GENERAL USES OF DIURETICS
1. Hypertension
2. Congestive cardiac failure
3. Edema

82. Adverse Effects of Diuretics
1. Dehydration
2. Electrolyte imbalance
3. Potassium deficiency
4. Headache
5. Dizziness
6. Renal damage
7. Cardiac arrhythmia
8. Heart palpitations

83. TYPES OF DIURETICS
1. Osmotic diuretics (Mannitol)
2. Diuretics which inhibit active reabsorption of
electrolytes
Loop, (Thick ascending loop of henle)
Thiazide, (Proximal part of DCT)
K sparing diuretics, (Distal part of DCT)

84. 3.Diureticswhichinhibitactionofaldosterone
(AldosteroneAntagonist)
4.Diureticswhichinhibitactivityofcarbonic
anhydrase(Acetazolamide)
5.Diureticswhichincreaseglomerularfiltration
rate(XanthineDerivative)
6. Diuretics which inhibit secretion of ADH
7. Diuretics which inhibit ADH receptors

86. OSMOTIC DIURETICS
Examples:
i. Urea
ii. Mannitol
iii. Sucrose
iv. Glucose

87. DIURETICS WHICH INHIBIT ACTIVE
REABSORPTION OF ELECTROLYTES
Loop Diuretics
i. Furosemide
ii. Torasemide
iii. Bumetanide
Thiazide Diuretics
i. Chlorothiazide
ii. Metolazone
iii. Chlortalidone
K Sparing Diuretics
i. Triamterene
ii. Amiloride

88. DIURETICS WHICH INHIBIT
ACTION OF ALDOSTERONE
These substances arealsocalledthe
potassium retainingdiureticsoraldosterone
antagonists.
Examples
i.Spironolactone
ii.Eperenone

89. DIURETICS WHICH INHIBIT ACTIVITY
OF CARBONIC ANHYDRASE
Acetazolamide isacarbonic anhydrase
inhibitor.
DIURETICS WHICH INCREASE
GLOMERULAR FILTRATIONRATE
i. Caffeine
ii. Theophylline

90. DIURETICS WHICH INHIBITSECRETION OF
ANTIDIURETIC HORMONE
i.Water
ii.Ethanol

92. DIALYSIS
Dialysisistheproceduretoremovewaste
materialsandtoxicsubstances andto
restorenormalvolumeandcompositionof
bodyfluidinsevererenalfailure.
Itisalsocalledhemodialysis.

93. ARTIFICIAL KIDNEY
Artificialkidneyisthemachinethatisusedto
carryoutdialysisduringrenalfailure.Itisused
totreatthepatientssufferingfrom:
1.Acuterenalfailure
2.Chronicorpermanentrenalfailure.

94. DIALYSATE
Theconcentrationofvarioussubstancesin
thedialysateisadjustedinaccordance with
theneedsofthepatient’sbody.
Thefluiddoesnotcontainurea,urate,sulfate,
phosphate orcreatinine,sothat,these
substances movefromthebloodtothe
dialysate.
Thefluidhaslowconcentrationofsodium,
potassium andchlorideionsthaninthe
uremicblood.Buttheconcentration of
glucose,bicarbonateandcalciumionsismore
inthedialysatethanintheuremicblood.

95. TYPES OF DIALYSIS
1.Hemodialysis
2.Peritoneal Dialysis

96. HEMODIALYSIS
Withhaemodialysis,thebloodisdrawn
andcleanedoutsideofthebody.
Amachinecalledadialyzerinconnected
throughaportinanarteryandveinina
person’sarm.
Themachinedrawsthebloodout,cleans
andbalancesitscomponents insidethe
machine,andcyclesitbackintothebody
itcamefrom.

97. Forthismethodofdialysis,thepatientto
besittingstillorlyingdownthroughout
theentireprocedure3-5timesaweek.
Afterdialysis,patientsoftenfeeltiredand
havelowbloodpressure.

98. PERITONEAL DIALYSIS
Peritonealdialysisisatypeofdialysisthat
occursinsidethebody.Morespecifically,
insidetheabdomen.
Afteracatheterisplacedintotheliningofthe
abdominal wall(alsoknown asthe
peritoneum)bloodcanbefilteredinternally.
Thepatientfillstheaccesspointwithafluid
calleddialysatefilter.Thedialysatefilterfluid
thencleans and balances theblood
components throughtheinternalabdominal
wallsandoncecomplete,drainsintoabag.

101. INTRODUCTION
Skinisthelargestorganofthebody.The
averagethicknessoftheskinisabout1
to2mm.
Skinismadeupoftwolayers:
I.Outerepidermis
II.Innerdermis.

102. EPIDERMIS
Epidermisistheouterlayerofskin.It
isformedbystratifiedepithelium.
Importantfeatureofepidermisisthat,
itdoesnothavebloodvessels.

103. Layers of Epidermis
Epidermis is formed by five layers:
1.Stratum corneum/ Horney Layer
(composed ofcorneocytes;i.e.deadcells,
andcontainkeratin,phospholipid and
glycogen)
2. Stratum lucidum
(flattened epithelial cells with
homogeneous translucentzone)

104. 3. Stratum granulosum
(Thinlayerofflattenedrhomboid cells.
Cytoplasmcontainsgranulesofaproteincalled
keratohyalin)
4. Stratum spinosum/ Prickle cell layer
(Spinelike protoplasmic projections)
5. Stratum germinativum
(Thicklayermadeupofpolygonalcells.New
cellsareconstantlyformedbymitoticdivision.
Thestemcells,whichgiverisetonewcells,
areknown askeratinocytes.Melanocytes
(presentb/wkeratinocyte)producethepigment
calledmelanin)

105. DERMIS
Dermisistheinnerlayeroftheskin.Itisa
connectivetissuelayer,madeupofdenseand
stoutcollagen fibers,fibroblasts and
histiocytes.Collagen fiberscontainthe
enzymecollagenase,whichisresponsiblefor
woundhealing.
Dermisismadeupoftwolayers:
1.Superficialpapillarylayer
2.Deeperreticularlayer

106. SUPERFICIAL PAPILLARYLAYER
Itcontainsbloodvessels,lymphaticsandnerve
fibers.Thislayeralsohassomepigment
containingcellsknownaschromatophores.
RETICULAR LAYER
Thesefibersarefoundaroundthehairbulbs,
sweatglandsandsebaceous glands.The
reticularlayeralsocontainsmastcells,nerve
endings,lymphatics,epidermal appendages
andfibroblasts.

107. COLOR OF SKIN
Colorofskindepends upon two
importantfactors:
1.Pigmentationofskin
2.Hemoglobinintheblood

108. PIGMENTATION OF SKIN
Cellsoftheskincontainabrownpigment
calledmelanin,whichisresponsibleforthe
coloroftheskin.Itissynthesized by
melanocytes.
Skinbecomes darkwhenmelanincontent
increases.Itisproteininnatureanditis
synthesizedfromtheaminoacidtyrosinevia
dihydroxyphenylalanine (DOPA).
Deficiencyofmelaninleadstoalbinism
(hypopigmentary congenitaldisorder).

109. HEMOGLOBIN IN THE BLOOD
Amountandnatureofhemoglobinthat
circulatesinthecutaneous blood
vesselsplayanimportantroleinthe
colorationoftheskin.

110. FUNCTIONS OF SKIN
PROTECTIVE FUNCTION
SENSORY FUNCTION
STORAGE FUNCTION
SYNTHETIC FUNCTION
REGULATION OF BODY TEMPERATURE
REGULATION OF WATER AND ELECTROLYTE
BALANCE
EXCRETORY FUNCTION
ABSORPTIVE FUNCTION
SECRETORY FUNCTION

111. GLANDS OF SKIN
1.SEBACEOUS GLANDS
Sebaceousglandsareovoidorsphericalinshape
andaresituatedatthesideofthehairfollicle.
Sebaceous glandssecreteanoilysubstance
calledsebum.developfromhairfollicles(Dermis
layer).
SebumcontainsFreefattyacids,Triglycerides,
Squalene,Sterols,Waxes,Paraffin.
Freefattyacidcontentofthesebum has
antibacterialandantifungalactions.Lipidnature
ofsebumkeepstheskinsmoothandoily.Lipidsof
thesebumpreventheatlossfromthebody.Itis
particularlyusefulincoldclimate.

112. 2. SWEAT GLANDS
Sweat glands are of two types:
1. Eccrine glands
2. Apocrine glands

114. BODY TEMPERATURE
Bodytemperaturecanbemeasuredbyplacing
theclinicalthermometer indifferentpartsof
thebodysuchas:
1.Mouth(oraltemperature)
2.Axilla(axillarytemperature)
3.Rectum(rectaltemperature)
4.Overtheskin(surfacetemperature)

115. VARIATIONS OF BODY
TEMPERATURE
Physiological Variations
1. Age
2. Gender
3. Diurnal variation
4. After meals
5. Exercise
6. Sleep
Pathological Variations
Hyperthermia/ Fever

118. HYPERTHERMIA
Elevationofbodytemperatureabovetheset
pointiscalledhyperthermia,feverorpyrexia.
Fever is classified into three categories:
1. Low-grade fever: When the body temperature
rises to 38°C to 39°C, (100.4°F to 102.2°F)
2. Moderate-grade fever:When the temperature
rises to 39°C to 40°C (102.2°F to 104°F)
3. High-grade fever: When the temperature rise
above 40°C to 42°C (104°F to 107.6°F).
4. Hyperpyrexiais the rise in body temperature
beyond 42°C (107.6°F).

119. Causes of Fever
1.Infection
2.Hyperthyroidism
3.Brain lesions
4.Diabetes insipidus

120. Signs and Symptoms
1. Headache
2. Sweating
3. Shivering
4. Muscle pain
5. Dehydration
6. Loss of appetite
7. General weakness.
Hyperpyrexia may result in:
1. Confusion
2. Hallucinations
3. Irritability
4. Convulsions.

121. HYPOTHERMIA
Decreaseinbodytemperaturebelow35°C(95°F)is
calledhypothermia.Whenthetemperature drops
below31°C(87.8°F),itbecomesfatal.
Hypothermiaisclassifiedintothreecategories:
1.Mildhypothermia:Whenthebodytemperature
fallsto35°Cto33°C(95°Fto91.4°F)
2.Moderatehypothermia:When thebody
temperaturefallsto33°Cto31°C(91.4°Fto87.8°F)
3.Severehypothermia:Whenthebodytemperature
fallsbelow31°C(87.8°F).

122. Causes of Hypothermia
1. Exposure to cold temperatures
2. Immersion in cold water
3. Drug abuse
4. Hypothyroidism
5. Hypopituitarism
6. Lesion in hypothalamus
7. Hemorrhage in certain parts of the
brainstem, particularly pons.