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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