II. Renal Function

Denielle Genesis B. Camato

II. RENAL FUNCTION ANALYSIS OF URINALYSIS AND BODY FLUIDS | REVIEWER

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RENAL BLOOD FLOW

!RENAL!ARTERY!

Each kidney is supplied with blood by a single renal artery that arises on its respective side of the aorta before dividing into fine segmented arteries that enters the HILUS within the kidney. Each segmented artery branches into several lobular arteries. The lobular arteries further subdivides into interlobular arteries which branched off into AFFERENT ARTERIOLE (blood enters); blood flows INTO the GLOMERULI (filter) through the afferent arteriole. Blood flows OUT of the GLOMERULUS through the EFFERENT ARTERIOLE (blood exits).

RENAL&VEIN&

URETHER&

URINE&FORMATION&

1. FILTRATION- of the blood by the glomerulus to form the ultra filtrate of the urine

2. TUBULAR REABSORPTION- of electrolytes and nutrients needed to make the consistency of the internal environments

3. EXCRETION of waste materials ----------------------------------------------------------------------------- FILTRATION -occurs as blood flows into the glomerulus from its afferent arteriole & plasma moves to the glomerular capillaries into the BOWMANS CAPSULE. From the glomerulus, the filtrate moves into the tubular segments of the nephron; here through TUBULAR REABSORPTION electrolytes and nutrients move from the filtrate back into the blood stream. Tubular secretion substances move from the peritubular capillaries into the urine filtrate. The filtrate concentrate passes into the collecting tubules then find its way to the renal pelvis where it is directed to the ureter, to the bladder, then to the urethra for elimination (EXCRETION).! URINE.

NEPHRON'

TUBULAR REABSORPTION & TUBULAR SECRETION REABSORPTION- is the movement of substances out of the tubules across the surrounding interstitial fluid into the blood of the capillaries. SECRETION- occurs in small amounts in the nephron; process whereby substances moved form the blood through the interstitial fluid into the tubule. ACTIVE TRANSPORT- responsible for the reabsorption of GLUCOSE, AMINO ACIDS and SALTS in the PROXIMAL CONVOULTED TUBULES and the reabsorption of CHLORIDE in the ascending loop of henle and SODIUM in the distal convoluted tubule. PASSIVE TRANSPORT- movement of molecules across a membrane as a result of differences in their concentration or electrical potential on opposite sides of the membrane. UREA and SODIUM; Proximal convoluted tubules and ascending loop of henle, ascending loop of henle.

!!

1! 2!

3! 4!

Most!component!of!the!blood!except!blood!cells!&!proteins!are!filtered!into!the!pores!of!the!glomerulus!before!reaching!the!Bowmans!capsule.!Glomerular!filtrates!contents.!

Waste!products.!Small!amounts!are!ok!but!harmful!in!large!doses.!

Next!desDnaDon!of!the!filtrate;!Twisted!or!‘coiled’!

Lines!the!proximal!convoluted!tubules!

5" 6"

7" 8"

65%"of"SODIUM"are"reabsorbed;"NaCl"or"‘table"salt’;"salty"outside"the"tubule.."

65%"water"leaves"by"OSMOSIS;"65%"potassium"is"reabsorbed"as"well"as"90%"bicarbonate"ions"which"are"impt"in"maintaining"the"pH"of"the"blood"(7.35M7.45)"

Glucose"&"Amino"acids"100&"reabsorbed"to"be"used"in"respiraTon"&"making"proteins;"not"all"UREA"(Passive'Transport)'"leaves"as"about"50%"is"reabsorbed."SECRETION?"Ammonia"&"drugs"are"secreted"into"the"tubules""

Ac1ve'transport'&'Passive'transport'

Ac1ve'transport'

LOOP'OF'HENLE;'"DescendingM"filtrates"travels"down"AscendingM"filtrate"travels"up"

Renal physiology Nephron

q 1 to 1.5 million functional units of the kidney Two types of Nephrons:

1) Cortical nephrons r 85% of nephrons; r Situated at the cortex of the kidney

2) Juxtamedullary nephrons

r longer Henle’s loops and extends deep into the medulla of the kidney

4 Essential Renal Functions:

r Renal blood flow r Glomerular filtration r Tubular reabsorption r Tubular secretion



2

13#14#

15# 16#

!in$order$to$prevent$cells$from$being$damaged$

Distal#convoluted#tubules#

!place$wherein$ini6al$adjustments$are$made$in$the$filtrate.$Under$the$influence$of$hormone$ALDOSTERONE…$

!Na$is$reabsorbed$followed$closely$by$Cl;$while$POTASSIUM,$all$hydrogen$ions$are$secreted$in$the$tubules.$Almost$all$remaining$bicarbonate$is$reabsorbed;$although$DCT$is$normally#impermeable#to#water:#small$amounts$maybe$reabsorbed$too..$

Collec<ng#ducts;#where$final$adjustments$takes$place#

!NaCl$is$reabsorbed$in$addi6on$to$Urea;$although$some6mes$Urea$can$RE!enter$the$tubules$at$the$loop$of$henle$(urea$recycling)$ $$$$$$UREA$

NaCl$

9"10"

11" 12"

&thin"line"of"the"loop"is"lined"

with"squamous"epithelial"

cells"

&region"wherein"it"is"highly"salty;"

WHY?"Because"sodium"is"acAvely"

pumped"out"

&descending"loop"is"permeable"to"h20;"but"has"very"low"permeability"to"

Na"&"urea;"so"as"filtrate"travels"down"

water"leaves"b/c"of"salty"

environment.."

Pumped"

out!"

..and"H20"cannot"follow"

because"ascending"loop"

is"(impermeable(to"water;"hence"the"

intersAAal"fluid"

becomes"salty"

..by"the"Ame"filtrate"reaches"the"end"of"

loop"its"highly"concentrated"because"of"

significant"amount"of"water"that"has"

leL."

&however"in"the"ascending"loop"water"

that"leaves"cannot"escape"the"

"filtrate."

&leaves"passively"

the"ascending"

loop"&"is"

pumped"out"

acAvely"of"the"

ascending"loop;"

&filter"

then"is"

diluted"

&in"total"25%"of"NaCl"is"

reabsorbed"in"the"LOOP"

of"HENLE"

17# 18#

19# 20#

!regulates*water*in*the*body.*Acts*to*retain*levels*of*water*in*the*body*by*reabsorp9on*

###DEHYDRATED#

“water*channels”*in*the*epithelium*allowing*H20*to*be*reabsorbed*

#####OVERHYDRATED##

***Medulla*is*SALTY*so*if*the*water*is*given*permission*to*leave..*It*WILL!*!*

!lack*of*ADH*means*collec9ng*duct*is*less*impermeable*to*H20*so*excess*water*can*passed*out*into*the*URINE!**

!in*general*URINE*contains*H20,*urea,*NaCl,*potassium*and*crea9nine..*

GLOMERULAR)FILTRATION)

RENAL&CORPUSCLE.))essen2al)for)the)filtra2on)of)blood)in)the)nephrons)of)the)kidney)

)

GLOMERULUS.)basically)a)network)of)the)capillaries;)“capillary)tuF”.)Located)within)the)BOWMAN’S)CAPSULE.)

Although)the))glomerulus)serves)as)a)nonselec2ve)filter)of)

plasma)substances)with)molecular)weights)of)less)than)

70,000,)several)factors)influence)the)actual)filtra2on)process.)

)

FACTORS:)

•  Structure)of)the)capillary)walls)&)Bowmans)capsule)

•  Hydrosta2c)and)Onco2c)pressures)•  Renin.Angiostenin.Aldosterone)system))

)

)

1" 2"

3" 4"

&essen*al"for"the"filtra*on"of"blood"in"the"nephrons"within"the"kidney"

&network"of"capillaries"“capillary"tu=”"

&components"of"the"blood"are"filtered"out;"“glomerular*filtrate”*

&fluid"that"enters"the"capsule"

&most"capillaries"have"an"‘arterial"end’"and"a"‘venous"end’""•  Afferent1"where"

blood"flows"FROM;"enters"

•  Efferent1"blood"flows"THROUGH;"exits"

5" 6"

7"8"

&where"filtra/on"occurs"

&kitchen"strainer;"water"and"other"small"par/cles"are"able"to"passed"through."In"glomerulus"molecules"<1.8"nm"(water,"sodium,"inulin,"glucose)"are"freely"filtered"out"while"those"that"are">3.6"are"not"filtered"(red"blood"cells,"haemoglobin..)"

Zoomed&in)sec,on)of)barrier)3)LAYERS)•  Capillary)wall)membrane)! Fenestra(ons&"pores;"lets"everything"through"except"for"blood"cells"

•  Basement)Membrane&"prevents"filtra/on"of"large"proteins"

•  Visceral)Epithelium)of))Bowmans)Capsule&"has"podocytes."Pedicels&"finger&like"projec/ons;"so"close"to"each"other"has"narrow""Slits"between"them;"allows"small"molecules"to"pass"through"

&barrier"is"charge&selec/ve;"difficult"for"nega/ve"molecules"to"pass"through"hence"albumin"is"not"filtered"despite"being"in"the"size"range.""""

9" 10"

11" 12"

&depends"on"a"balance"that"favours"the"filtra8on"and"those"that"opposed"it"

&refers"to"the"force"a"fluid"exerts"on"the"walls"of"its"compartments;"eg:"water"pushing"inside"the"water"balloon"but"fluid"can"be"pushed"out."

&pressure"exerted"by"plasma"protein"on"walls"in"which"they"are"contained;"sponge&like"effect"encouraging"fluid"to"be"drawn&in"hence"""""‘pulling’"

&major&driving&force&for&filtra2on;&forces&fluid&out&of&capillary&

&opposes"the"hydrosta8c"force"of"the"capillary""

&of"BOWMAN’S"Capsule"

13#14#

15# 16#

'#We#tend#to#ignore#onco2c#pressure#of#the#bowmans#capsule#as#only#2ny#amounts#of#protein#are#usually#present#in#the#glomerular#filtrate#

NFP$#equals#the#pressure#favouring#filtra2on:###•  minus&the#pressures#

opposing#filtra2on#(eg:%hydrosta.c%pressure%of%the%glomerulus)%%

•  minus#hydrosta2c#pressure#of#the#bowmans#capsule##

•  minus&the#pressure#of#the#glomerular#onco2c#protein#which#is#equals#to…#

610%mmHg%of%mercury..%

'there#are#many#nephrons#hence#there#are#many#‘renal#corpuscles’#in#the#kidney.###GFR'#refers#to#the#total#amount#of#the#filtrate#all#formed#by#the#renal#corpuscle#in#both#kidneys#per#minute# 'can#be#used#to#assessed#as#a#clue#

whether#an#individual#has#renal#impairment.#

GFR#accounts#for..#

##And&permeability&of&&glomeruli!&#

•  The#standard#test#used#to#measure#the#filtering#capacity#of#the#glomeruli#is#the#clearance+test.+As#its#name#implies,#a#clearance#test#measures#the#rate#at#which#the#kidneys#are#able#to#remove#(to#clear)#a#filterable#substance#from#the#blood.##



3

17#18#

19# 20#

GFR=#product#of#surface#area#and#permeability#mul*plied-by#NFP.##

.filtra*on-coefficient-mul=plied#by#NFP-

##

The#GFR#is#reported#in#mL/min;#therefore,#determining#the#number#of#milliliters#of#plasma#from#which#the#clearance#substance#(crea=nine)#is#completely#removed#during#1#min#is#necessary#

Kpermeability#of#surface#area#of#glomeruli#tends#to#be#greater#b/c#of#fenestra=ons#and..#

21# 22#

23#

Example:#if#we#constrict#the#afferent#arteriole;##the#hydrosta;c#pressure#of#the#blood#will#decrease#due#to#the#reduc;on#of#blood;#as#this#pressure#is#associated#with#NFP,#this#will#also#decrease#so#as#GFR..#

Glomerulus#&#bowmans#capsule#is#highly#specialized#in#filtra;on#of#blood#and..#

GFR#is#a#good#indicator#as#to#how#well#the#kidney’s#are#working..#

KEY$NOTES:$•  When# interpre;ng# the# results# of# a# crea;nine# clearance# test,# the# GFR# is#determined#not# only# by# the# number# of# func;oning# nephrons# but# also# by# the#func;onal#capacity#of#these#nephrons.#

•  Currently,# rou;ne# laboratory#measurements# of#GFR# employ# crea;nine# as# the#test# substance.# Crea;nine,# a# waste# product# of# muscle# metabolism# that# is#normally# found# at# a# rela;vely# constant# level# in# the# blood,# provides# the#laboratory#with#an#endogenous#procedure#for#evalua;ng#glomerular#func;on.#

•  Therefore,# although# the# crea;nine# clearance# is# a# frequently# requested#laboratory# procedure,# its# value# does# not# lie# in# the# detec;on# of# early# renal#disease.# Instead,# it# is# used# to# determine# the# extent# of# nephron# damage# in#known# cases# of# renal# disease,# to# monitor# the# effec;veness# of# treatment#designed#to#prevent#further#nephron#damage,#and#to#determine#the#feasibility#of#administering#medica;ons,#which#can#build#up#to#dangerous#blood# levels# if#the#GFR#is#markedly#reduced.#

LOOP OF HENLE.MP4

Source: https://www.youtube.com/watch?v=8UVlXX-9x7Q https://www.youtube.com/watch?v=9A2dAyWyK6o https://www.youtube.com/watch?v=cYyJF_aSC6o

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II. Renal Function