Filter ~180 liters of blood plasma daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine1- Regulate volume and chemical composition of the bloodblood2- Maintain the proper balance between water and salts ( Osmolality ) .salts ( Osmolality ) .3- Maintain the proper acid base balance .4- Maintain the proper plasma concentration of 4- Maintain the proper plasma concentration of glucose by gluconeogenesis5- play an important role to maintain the normal blood 5- play an important role to maintain the normal blood pressure

Urinary and Plasma Concentrations of Urinary and Plasma Concentrations of Some Physiologically Important Substances emphasizes the manner by which the kidneys emphasizes the manner by which the kidneys

conserve important electrolytes and metabolites while wastes are eliminated in the urinewhile wastes are eliminated in the urine

U/P ratioUrine(U)Plasma(P)Sbstances U/P ratioUrine(U)Plasma(P)Sbstances

00100Glucose (mg/dL) 00100Glucose (mg/dL)

0.690140Na+ (mEq/L)

6090015Urea (mg/dL)

1501501Creatinine (mg/dL)

The balancebetween intake and output is maintained in maintained in large part by the kidneys: the kidneys: Effect of 10-

fold increase in fold increase in sodium intake

on urinary on urinary sodium

excretion and excretion and extracellular fluid volume.

Production of rennin to help regulate blood pressure Production of erythropoietin to stimulate RBC Production of erythropoietin to stimulate RBC productionActivation of vitamin D3 (calcitriol) Activation of vitamin D3 (calcitriol)

25 OH- Cholecalciferol 1,25 DOH- Cholecalciferol

Pa ra cr in e s ecret ion of p ros ta gla n d in s , k in in s , Trom boxa n A2 ,En doth elin , n it r ic k in in s , Trom boxa n A2 ,En doth elin , n it r ic oxide ( NO ), Aden os in e & Urod ila t in lea d in g m a in ly to m odu la t ion of ren a l b lood flowm a in ly to m odu la t ion of ren a l b lood flow

Afferent nerves involveAfferent nerves involvein renal pain sensation, uretero-renal & renorenal reflexes renorenal reflexes

Efferent nerves: parasympathetic cholinergic n. from Vague sympathetic postganglionic from S.M.G. & renal plexussympathetic postganglionic from S.M.G. & renal plexusMostly noradrenergic ( some NANC ) to interlobular A. afferent a. & some in efferent a. Acting on to interlobular A. afferent a. & some in efferent a. Acting on

1 & in less extent on 2 postsynaptic .To juxtaglomerular apparatus (JGA ) via 11To PT, Thick AL, DT &CD via or

Renal blood flow(RBF), it s regional distributionRenal blood flow(RBF), it s regional distribution

Approximately one-fourth (1200 Approximately one-fourth (1200 ml) of systemic cardiac output(CO) flows through the

Cortex

Outer

output(CO) flows through the kidneys/minute Renal Fraction =RBF/CO 100 Outer

MedullaRenal Fraction =RBF/CO 100

Overall RBF= 3.5 ml/g tissue/min

Inner Medulla

tissue/minIn cortex 5 ml/g tissue/minIn outer medulla 2.5 ml/g In outer medulla 2.5 ml/g tissue/minIn inner medulla 0.6 ml/g For comparison blood flow

for the Brain is 0.5 ml/g tissue/min

In inner medulla 0.6 ml/g tissue/min

RBF depends on the total renal vascular resistance:

Per Cent of Total Pressure in Vessel Per Cent of Total Renal Vascular

Resistance

Pressure in Vessel (mm Hg)

Vessel

ResistanceEnd Beginning

~0~100100Renal artery

~1685~100Interlobar, arcuate, and interlobular arteries

~266085Afferent arteriole

~15960Glomerular capillaries

~431859Efferent arteriole

~10818Peritubular capillaries ~10818Peritubular capillaries

~448Interlobar, interlobular, and arcuate veins arcuate veins

~0~44Renal vein

Renal vasoconstriction - RBFEpinephrine & NorepinephrineEpinephrine & NorepinephrineAngiotensin II-produced by JGA (affects E.a. more than A.a.)EndothelinEndothelinAdenosineADHT.A -constricts A.a.T.A2 -constricts A.a.

Renal vasodilatation - RBF Prostaglandins - PgE and PgI ( BF in cortex but in Prostaglandins - PgE2 and PgI2 ( BF in cortex but in medulla )Ach Ach NO Dopamine Glucocorticoids - dilates A.a.Glucocorticoids - dilates A.a.High protein diet

Urine formation and adjustment and adjustment of blood composition composition involves 4 major processes processes

1. Glomerular filtrationfiltration

2. Tubular reabsorptionreabsorption

3. TubularSecretionSecretion

4. Excretion

fi ltration occurs at FiltrationMembrane Membrane

Glomerular Filtration Rate (GFR) =The total amount of filtrate formedThe total amount of filtrate formedper minute by 2 kidneys

~125 ml/min which is 15-20% of RPF

fi ltration fraction = the fi ltration fraction = the portion of p lasm a th at is fi lte re d/m in fi lte re d/m in = ( GFR/RP F ) x 100 = (125/700 ) x 100 = 17.3%(125/700 ) x 100 = 17.3%

Factors affecting the filterability of differentfilterability of differentparticles

Filterability of negativelyFilterability of negativelyCharged particles innormal & abnormal normal & abnormal conditions

Filtrate in Bowman s spaceFiltrate in Bowman s spaceFiltration barrierGlomerular capillary plasma

-

+

++

+ -

-

++-

--

NegativelyCharged proteins

+

+

++

+

+ -+

+ +

+- -proteins +

+

++

+

- ++

++-

- -

-

-- +

+-

-

-

--

-- +

--

GFR = Kf NFP=(A D /T) NFPNFP

A=Total surface area available for filtrationfiltrationD=Filtration membrane permeabilityT=Filtration membrane thickness NFP =Net filtration pressureNFP =Net filtration pressure

= PGC ( GC +PT)=

60 - ( 32 + 18 )=10 mmHg

Effect of changes in A & E arteriolar resistance on GFR & RBF on GFR & RBF

f

Contraction via IP3leads Relaxation via Contraction via IP3leads to in G.S.A.

1. E & NE

Relaxation via

cAMP or cGMP leads to1. E & NE

2. Ag II3. ADH

leads toin G.S.A.

3. ADH4. P.D.G.F.5. P.A.F.

in G.S.A.1. ANP2. Dopamine

5. P.A.F.6. PG F27. T A

2. Dopamine 3. PG. E24. NO

7. T A28. Leukoterians C & D9. Histamine

4. NO5. Urodilatin

9. Histamine10. Endothelins

P =Hydrostatic PGC =Hydrostatic pressure in Glomerular capillaryGlomerular capillaryPT = Hydrostatic PT = Hydrostatic pressure in Bowman's capsule

A BC

Bowman's capsule

GC = Colloid Osmotic Pressure in

Intra Glomerular Equilibration point

Osmotic Pressure in Glomerular capillaryP = Net Ultra PUF = Net Ultra filtration Pressure

Increase in the rate plasma colloid osmotic pressure rises along the glomerular capillary pressure rises along the glomerular capillary

depends on the ltration fraction

GFR = Kf NFP=(A D /T) NFPNFP

A=Total surface area available for filtrationfiltrationD=Filtration membrane permeabilityT=Filtration membrane thickness NFP =Net filtration pressureNFP =Net filtration pressure

= PGC ( GC +PT)=

60 - ( 32 + 18 )=10 mmHg

f

Contraction via IP3leads Relaxation via Contraction via IP3leads to in G.S.A.

1. E & NE

Relaxation via

cAMP or cGMP leads to1. E & NE

2. Ag II3. ADH

leads toin G.S.A.

3. ADH4. P.D.G.F.5. P.A.F.

in G.S.A.1. ANP2. Dopamine

5. P.A.F.6. PG F27. T A

2. Dopamine 3. PG. E24. NO

7. T A28. Leukoterians C & D9. Histamine

4. NO5. Urodilatin

9. Histamine10. Endothelins

Effect of changes in A & E arteriolar resistance on GFR & RBF on GFR & RBF

P =Hydrostatic PGC =Hydrostatic pressure in Glomerular capillaryGlomerular capillaryPT = Hydrostatic PT = Hydrostatic pressure in Bowman's capsule

A BC

Bowman's capsule

GC = Colloid Osmotic Pressure in

Intra Glomerular Equilibration point

Osmotic Pressure in Glomerular capillaryP = Net Ultra PUF = Net Ultra filtration Pressure

Increases in the ltration fraction increase the rate at which the plasma colloid osmotic rate at which the plasma colloid osmotic

pressure rises along the glomerular capillary

Tow types of mechanisms control Tow types of mechanisms control the RPF & GFR

A-Extrinsic mechanisms 1- Neural control 1- Neural control 2- Hormonal control

rennin -Angiotensin systemsystem

B-Intrinsic mechanisms ( Renal auto regulation )

1-Tubuloglomerular 1-Tubuloglomerular Feedback

2- Myogenic Mechanism

Extrinsic mechanisms

BPGFRNaCL intake by M.D. cells

mechanisms involved in GFR

Neural Control

Hormonal Control GFR

regulation

Control

Ag II

Constriction of Efferent arterioles In kidneys

GFR

Stimulators E & NEProstaglandins Prostaglandins

Inhibitors Increased NaCL reabsorption across Macula DensaDensaIncreased afferent arteriolar pressureAngiotensin II VasopressinVasopressin

Myogenic MechanismTubuloglomerular Feedback

or RBP or GFR

or Fluid Delivery To JGAA) Na Cl intake by MD

T-A2 , paracrine secretion of T-A2 , ATP or Adenosine

Afferent Arteriole constriction Afferent Arteriole constriction

RBF & GFRB) Na Cl intake by MD paracrine B) Na Cl intake by MD paracrine

secretion of NO Afferent Arteriole Dilation RBF & GFRDilation RBF & GFR

GFR P + TGFR PX+T -TGFR PX + TS

=UX VU+TS -TR=UX VU

GFR PX -TR=UX VU

GFR PX=VU UX

TR

TSTS

TX = VariableUX VU = Variable

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