Kidney Kidney The kidney performs excretory & endocrinal functions The kidney performs excretory & endocrinal functions such as ;eliminate waste products from the body, regulate such as ;eliminate waste products from the body, regulate both erytheroposis, arterial blood pressure .are essential both erytheroposis, arterial blood pressure .are essential for homeostasis (regulation of body water content) .the for homeostasis (regulation of body water content) .the blood levels of both electrolyte and non electrolytes, and blood levels of both electrolyte and non electrolytes, and the acids base balance.the acids base balance.

Excretory functions of the kidney;Excretory functions of the kidney; thethe kidney clear the plasma from kidney clear the plasma from

unwanted substance which includes; Non unwanted substance which includes; Non essential substance ,end products of essential substance ,end products of metabolism as urea ,uric acids and metabolism as urea ,uric acids and

creatinin & bilirubin creatinin & bilirubin

Foreign substance as drugs ,toxins .Foreign substance as drugs ,toxins .Excess amount of essential Excess amount of essential

substance ;water, electrolyte (na ,k).substance ;water, electrolyte (na ,k).

Endocrine function of the kidneyEndocrine function of the kidneyThey secret rennin & erythropoietin, and form prostaglandins,1-25 They secret rennin & erythropoietin, and form prostaglandins,1-25 dihydroxycholecalciferoldihydroxycholecalciferol..

RenninRennin This is secreted by juxtaglomerular cells .It is glycoprotein's which is This is secreted by juxtaglomerular cells .It is glycoprotein's which is

acts on angiotensinogen ( which is synthesized by the liver ) acts on angiotensinogen ( which is synthesized by the liver ) leading to formation of leading to formation of angiotensin1angiotensin1 which is converted to which is converted to angiotensin11angiotensin11 which produce several effects :generalized which produce several effects :generalized

vasoconstriction , stimulation of aldosterone formationvasoconstriction , stimulation of aldosterone formation. . Rennin secretion is stimulated by renal ischemia ,in case of Rennin secretion is stimulated by renal ischemia ,in case of

hypotension., increased sympathetic activity and by certain hypotension., increased sympathetic activity and by certain prostaglandinsprostaglandins. .

ErythropoietinErythropoietin It is a glycoprotein ,secreted by endothelial cell of peritubular It is a glycoprotein ,secreted by endothelial cell of peritubular

capillaries in the renal cortexcapillaries in the renal cortex. . It is increase number of committed stem cell in the bone marrow that It is increase number of committed stem cell in the bone marrow that is converted into red cell precursor and subsequently into mature is converted into red cell precursor and subsequently into mature red blood cellsred blood cells. .

It is secretion is stimulated by hypoxia ,cobalt salts, androgens and is It is secretion is stimulated by hypoxia ,cobalt salts, androgens and is facilitate by adenosine catecholamine, and by alkalosis. That facilitate by adenosine catecholamine, and by alkalosis. That

develop at high altitudedevelop at high altitude

ProstaglandinProstaglandin Act on auto regulation of glomerular filtration rate Act on auto regulation of glomerular filtration rate

& renal blood flow and stimulate rennin secretion& renal blood flow and stimulate rennin secretion The kidney secretes two types of prostaglandins : The kidney secretes two types of prostaglandins :

PG 1& PG11PG 1& PG11..

1,251,25 DihydroxycholechalciferolDihydroxycholechalciferol ;;This is active form of vitamin DThis is active form of vitamin D

It is formation is facilitated by parathyroid It is formation is facilitated by parathyroid hormoneshormones

It is released into the blood stream where it It is released into the blood stream where it produce its effects in the intestine and boneproduce its effects in the intestine and bone. .

Renal circulationRenal circulation The kidney receive the arterial blood via the renal artery which arises directly The kidney receive the arterial blood via the renal artery which arises directly

from aorta it breaks into interlobar arteries in the medulla break into from aorta it breaks into interlobar arteries in the medulla break into interlobular which inter the cortex and then divide into interlobularinterlobular which inter the cortex and then divide into interlobular

Renal blood flowRenal blood flow Normally R.B F is about 1200ML/Minute, the flow is much greater in the Normally R.B F is about 1200ML/Minute, the flow is much greater in the

cortex ,only about 2% pass in the vasa recta resulting in a sluggish flow in cortex ,only about 2% pass in the vasa recta resulting in a sluggish flow in the renal medulla , which is important in the process on urine formationthe renal medulla , which is important in the process on urine formation. .

Control of R .B FControl of R .B F

R .B .FR .B .F Is Is directly proportionaldirectly proportional to to A.B PA.B P .↑RBF ↑ABP .↑RBF ↑ABP And inversely proportional to renal vascular resistance And inversely proportional to renal vascular resistance (R.V.R) which is determined by the diameter of (R.V.R) which is determined by the diameter of glomerular afferent & efferent arterioleglomerular afferent & efferent arteriole..Catecholamine'sCatecholamine's ,strong sympathetic stimulation cause ,strong sympathetic stimulation cause renal vasoconstriction specially the afferent arteriole renal vasoconstriction specially the afferent arteriole

lead to ↑RVR so leads to ↓R B Flead to ↑RVR so leads to ↓R B F . .Acetyl choline & other vasodilator Acetyl choline & other vasodilator drugsdrugs ,caffeine ,↑RBF leads to ↓RVR ,caffeine ,↑RBF leads to ↓RVR..ProstaglandinsProstaglandins ↑blood flow in the renal cortex & ↓in the ↑blood flow in the renal cortex & ↓in the renal medullarenal medulla. .

AngiotensinAngiotensin cause vasoconstriction particularly the cause vasoconstriction particularly the efferent arteriole leads to ↑RVR &↓RBFefferent arteriole leads to ↑RVR &↓RBF..

__Renal blood flowRenal blood flow The renal blood flow can be measure by either: 1- ElectromagneticThe renal blood flow can be measure by either: 1- Electromagnetic..

22 - -Determination of renal plasma flow 3-.Haematocriet valueDetermination of renal plasma flow 3-.Haematocriet value

Renal plasma clearanceRenal plasma clearance It is the amount of plasma in ml which is cleared off or removed from a It is the amount of plasma in ml which is cleared off or removed from a

certain substance per minutes by both kidneyscertain substance per minutes by both kidneys..c=uxv/pc=uxv/pC=Renal plasma clearanceC=Renal plasma clearance. . U=Urine concentration of the substance ⁄ mg ⁄mlU=Urine concentration of the substance ⁄ mg ⁄ml V = Volume of urine in ml/min which is determined by introducing V = Volume of urine in ml/min which is determined by introducing catheter into urinary bladdercatheter into urinary bladder. . P= plasma con of substance in mg/mlP= plasma con of substance in mg/ml This equation is called( Ficks principle ) methodsThis equation is called( Ficks principle ) methods . .

The clearance value in not the same depending upon what is happen The clearance value in not the same depending upon what is happen in the nepheronin the nepheron. .

Substance that are secreted by the renal tubules have high clearance Substance that are secreted by the renal tubules have high clearance value, while those reabsorbed have low clearance valuevalue, while those reabsorbed have low clearance value. .

If the substance is secreted from the tubules, the clearance value will If the substance is secreted from the tubules, the clearance value will be higher than inulin clearance , if the secretion is complete the be higher than inulin clearance , if the secretion is complete the clearance value equals 700ml/minclearance value equals 700ml/minIf clearance value more than 700 ml/ min this means that the If clearance value more than 700 ml/ min this means that the substance is synthesized by the tubulessubstance is synthesized by the tubules..

Inulin clearanceInulin clearanceIt is used to measure glomerular filteration rate (G.F.R)It is used to measure glomerular filteration rate (G.F.R)..

Inulin is a polymer of fructose with low molecular Inulin is a polymer of fructose with low molecular weight .it is neither reabsorbed nor secreted, but it is weight .it is neither reabsorbed nor secreted, but it is freely filtered , it is not toxic, it is freely permeable by freely filtered , it is not toxic, it is freely permeable by the glomeruli, it is not utilized by the tissue., it is not the glomeruli, it is not utilized by the tissue., it is not enter the red cellsenter the red cells. .

It is easily measure in plasma so its concentration in It is easily measure in plasma so its concentration in plasma = its concentration in filtratesplasma = its concentration in filtrates

Also the amount of inulin filtered /min = its amount Also the amount of inulin filtered /min = its amount excreted in urine/minexcreted in urine/min..

The inulin clearance is about 130 ml/minThe inulin clearance is about 130 ml/min

Significance ; measure G.F.RSignificance ; measure G.F.R . .

Determination of renal blood flowDetermination of renal blood flowIt is used by two substanceIt is used by two substance; ;

11--DiodrastDiodrast . .22--PAHA(para-amino-hipuric –acids )PAHA(para-amino-hipuric –acids )

When these substance are present in certain When these substance are present in certain concentration in plasma not more than 2mg/ml concentration in plasma not more than 2mg/ml

plasma they are completely removed by the plasma they are completely removed by the kidneykidney. .

Sample of renal venous bloodSample of renal venous blood can be obtained in can be obtained in man by introducing a cardiac catheter into cubital man by introducing a cardiac catheter into cubital

vein to the right atrium to inferior vena cava to vein to the right atrium to inferior vena cava to renal veinrenal vein..

Renal venous blood contain traces of PAHARenal venous blood contain traces of PAHA..Renal plasma flowRenal plasma flow= 14(con of PAHA in urine ) = 14(con of PAHA in urine )

/0.02(con of PAHA in plasma )=700ml/min/0.02(con of PAHA in plasma )=700ml/minRenal blood flowRenal blood flow = Renal plasma flow X 1/1-HV = Renal plasma flow X 1/1-HV

==700X1/1-0.55=700X1/1-0.55=1273ml/min1273ml/min..

Creatinine clearanceCreatinine clearance It is freely filtered in the glomeruli then partially secreted in It is freely filtered in the glomeruli then partially secreted in the proximal convoluted tubule ,and it is not reabsorbedthe proximal convoluted tubule ,and it is not reabsorbed. .

Because creatinine is partially secreted ,the excreted amount Because creatinine is partially secreted ,the excreted amount in urine uxv is more than filtrates , normally 140 ml/minin urine uxv is more than filtrates , normally 140 ml/min . .

TestTest::Creatinine clearance depend on the daily product of Creatinine clearance depend on the daily product of

creatinine (produce from muscle metabolism )which is creatinine (produce from muscle metabolism )which is constant and not affected by protein intakeconstant and not affected by protein intake. .

UrineUrine is collected over 24 hours for measure of urinary is collected over 24 hours for measure of urinary creatininecreatinine. .

Blood plasmaBlood plasma are taken through the day .average plasma is are taken through the day .average plasma is determined about 3 samples,one in the morning ,one determined about 3 samples,one in the morning ,one

afternoon ,one in the evening .because its varies during the afternoon ,one in the evening .because its varies during the day according to ms exercise .creatinine clearance is day according to ms exercise .creatinine clearance is

determineddetermined

ImportanceImportance;;With progressive renal failure decrease creatinine clearanceWith progressive renal failure decrease creatinine clearance . .

Urea clearanceUrea clearance IT is freely filtered in the glomeruli .then partially reabsorbed (back IT is freely filtered in the glomeruli .then partially reabsorbed (back

diffusion) In the tubules and it is not secreteddiffusion) In the tubules and it is not secreted Because urea is partially reabsorbed ,the excreted amoumt in the Because urea is partially reabsorbed ,the excreted amoumt in the urine is less than filtered .so its clearance value will be smaller urine is less than filtered .so its clearance value will be smaller

than inulin clearance .the amount of excreted urea depend upon than inulin clearance .the amount of excreted urea depend upon the rate of urine flow ,the greater the urine flow the less will be the the rate of urine flow ,the greater the urine flow the less will be the

back diffusion &the more will be the amount of urea excretedback diffusion &the more will be the amount of urea excreted. . If the volume of urine is 2ml or moreIf the volume of urine is 2ml or more ,the excretion of urea is maximal ,the excretion of urea is maximal

and the usual formula of plasma clearance test is used and the usual formula of plasma clearance test is used 75ml/min75ml/minIf the volume is 2 mlIf the volume is 2 ml the standard clearance formula is used .c=uxv/P the standard clearance formula is used .c=uxv/P

TestTest11 - -The subject evacuate his bladder ,then he drink a glass of waterThe subject evacuate his bladder ,then he drink a glass of water..

22 - -One hour later a blood sample is taken(, to measure p),Urine is One hour later a blood sample is taken(, to measure p),Urine is collected and he drink another glass of watercollected and he drink another glass of water..

33--After another hour, urine is again collected and average volume After another hour, urine is again collected and average volume /min & urea are calculated/min & urea are calculated. .

If v is 2ml or more maximal clearance is usedIf v is 2ml or more maximal clearance is used If v is less than 2 ml standard clearance formula is usedIf v is less than 2 ml standard clearance formula is used. .

C= uC= ux√v/p=54ml/minx√v/p=54ml/min