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Renal system. Renal system function of the kidney.

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Presentation on theme: "Renal system. Renal system function of the kidney."— Presentation transcript:

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2 Renal system

3 function of the kidney

4 function of the kidney :
Formation of urine . 1- Role in homeostasis: Primary function of kidneys is homeostasis such as : Excretion of waste products Urea,Uric acid,Creatinine andBilirubin Maintain water balance *conserving water when =decreased *Excreting water when = excess in the body Maintain electrolytes (Na) Especially sodium is in relation to water balance Maintain acid-base balance PH in the blood and body fluid maintained in normal range

5 function of the kidney :
2- Hemopoeitic function: secrete erythropoeitin for erythrocytes -secrete thrompopoeitin for thrombocytes 3-Endocrine function: erythropoeitin, thrompopoeitin, renin 4-Regulation of blood pressure Regulating ECF(extracellular fluid ) volume Renin –angiotensin mechanism 5- Regulation of blood calcium level activate vitamin D necessary for absorption of calcium from intestine to blood.

6 NEPHRON

7 1- renal corpuscle It is structural and functional unit of kidney.
Nephron It is structural and functional unit of kidney. Types of nephron: 1- cortical nephron: in outer cortex 2- juxtamedullary nephron: inner cortex Each nephron is formed from: 1- renal corpuscle The function of renal corpuscle is filtration of blood  first phase of urine formation 2- renal tubule

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9 Structure of Renal corpuscle Two portions:
1- glomerulus Tuft of capillaries enclosed by Bowman capsule These capillaries are disposed between afferent arteriole and efferent arteriole 2- Bowman capsule Is like a funnel with filter paper Is formed by two layer: The inner  visceral layer The outer  parietal layer

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11 Renal tubule Is the continuation of Bowman capsule
Consists of 3 part : -proximal convoluted tubule (PCT) -loop of Henel: Descending limb, Hairpin bend, Ascending limb -Distal convoluted tubule (DCT)

12 Juxtaglomerular apparatus
organ situated near glomerulus of each nephrone 3 structures: 1 macula densa 2 extraglomerular mesangial cell 3 juxtaglomerular cells Function : Primary function is secretion of hormonal sub 1- secretion of renin 2- secretion of other substances (PGs) 3- regulation of GBF and GFR

13 Renin- angiotensin system
Renin released into the blood Angiotensinogen renin angiotensin I ACE(lung) angiotensin II angiotensinase(RBCs) angiotensin III Functions of Angiotensin II: Increase blood pressure by vasoconstriction Stimulate adrenal cortex to secrete aldosterone Regulate glomerular filtration Increase water intake by stimulating the thirst center Increase secretion antidiuretic hormone from hypothalamus

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15 Renal circulation Renal blood vessels
Renal artery from abdominal aorta and enter the kidney through the hilus Regulation of renal blood flow: By Autoregulation. Autoregulation : The ability of an organ to regulate its own blood flow Present in some vital organs in the body such as brain, heart and kidneys 1- Myogenic response 2- tubuloglomerular feedback

16 URINE FORMATION

17 Urine formation Introduction :
Urine formation is a blood cleansing function. Normally about 26% of cardiac output enters the kidneys to get rid of unwanted substances Kidneys excrete the unwanted substances in urine Normally about 1 to 1.5 L( ml) of urine is formed every day The mechanism of urine formation includes three processes : Glomerular filtration Tubular reabsorption Tubular secretion

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19 Mechanism of Urine formation
I-Glomerular filteration: Definition Glomerular filtration is the process by which the blood that passes through glomerular capillaries is filtered through the filtration membrane Filteration membrane: Formed by 3 layer : Glomerular capillary membrane Basement membrane Visceral layer of bowman capsule

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22 Process of glomerular filtration :
All substances of plasma even the minute particles are filtered except plasma proteins due to their large molecular size (ultrafilteration). The filtered fluid is called glomerular filtrate The glomerular filtrate contain all the substance of plasma except the Plasma proteins Glomerular filtration rate (GFR) Total quantity of filtrate formed in all nephrons of both kidneys in the given unit of time The normal (GFR) (125mL/min)or (180 L/ day) Filteration fraction: Is the fraction (portion) of the renal plasma which becomes the filtrate It is the ratio between renal plasma flow and glomerular filtration rate It is expressed in percentage = GFR/RPF X 100

23 Factors affecting GFR 1-renal blood flow (RBF):
It is the most important factor for glomerular filtration 2-Tubuloglomerular feedback: Is the mechanism that regulate GFR 3-Glomerular capillary pressure: Pressure exerted by blood in glomerular capillary 4-Colloidal osmotic pressure: Pressure exerted by plasma protein in the glomeruli 5-Hydrostatic pressure in bowman capsule: Pressure exerted by filterate in Bowman capsule 6-Constriction of afferent & efferent arteriole: The Constriction of afferent arteriole reduces the blood flow to the glomerular capillary . If efferent arteriole is constricted, the GFR increases because of stagnation of blood in the capillaries.

24 7-Systemic arterial pressure: 8-Sympathetic stimulation:
afferent & efferent arteriole are supplied by sympathetic nerves. Strong sympathetic stimulation cause sever constriction of the blood vessels 9-Surface area of capillary membrane: 10-Permeability of capillary membrane: 11-Hormonal: increase GFR by vasodilatation: prostaglandin (PGE2) decrease GFR by vasoconstriction: (Angiotensin II)

25 II- Tubular reabsorption 2- passive reabsorption
Definition Tubular reabsorption is the process by which water and other substances are transported from renal tubules back to the blood . Selective reabsorption Essential substances such as glucose , amino acids and vitamins . Substances like metabolic waste products are excreted through urine. Mechanism: 2- passive reabsorption 1- active reabsorption Is the movement of molecules along the electrochemical gradient . does not need energy . substances reabsorbed  urea, water Is the movement of molecules against the electrochemical gradient . it needs energy (ATP) substances reabsorbed  sodium, calcium ,potassium

26 Regulation of tubular reabsorption:
1-Glomerulotubular balance Is the balance between the filtration and reabsorption of solutes and water in kidney. 2-Hormonal factor Which regulate GFR. Aldosterone Angiotensin ll Antidiuretic hormone 3-nervous factor Activation of sympathetic nervous system increase the tubular reabsorption Transport maximum (Tm) value: The rate at which a substance is reabsorbed from the renal tubule. 375mg/min for males 300mg/ min for females

27 Reabsorption of important substances:
sodium: 99% reabsorbed water: from proximal convoluted tubule (PCT): obligatory water reabsortption from distal convoluted tubule and collecting duct (DCT): facultative water reabsorption glucose: Is completely reabsorbed in the proximal convoluted tubule Renal threshold for glucose: Is 180mg/dl in venous blood . When blood level for glucose reaches 180 mg/dL, glucose is not reabsorbed completely and appear in urine. bicarbonate : mostly in proximal tubule in the form of CO2

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29 III- tubular secretion
Is the process by which the substance are transported from blood into renal tubules Substances secreted in renal tubules : Potassium Ammonia Hydrogen ions

30 Concentration & Dilution of urine

31 Concentration of urine
Osmolarity of glomerular filtrate is same as that of plasma and it is 300 mOsm/L. Normally urine is concentrated and its osmolarity is 4 times more than that of plasma mOsm/L. Depends on two factors: Water content in the body. Antiduiretic hormone . When the water content in body decreases kidney retains water and excretes concentrated urine Formation of concentrated by Secretion of ADH

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33 Formation of dilute urine
If water content in the body is more , kidney excretes excess water making the urine dilute . ADH increases the water reabsorption from renal tubule and collecting duct resulting in concentration of urine . When the volume of body fluid increases or the osmolarity of body fluid decreases ,ADH secretion stops so water reabsorption from renal tubules dose not take place Leads to excretion of large amount of water urine making the urine dilute

34 Role of ADH The final concentrated of urine is achieved by ADH
Normally the distal convoluted tubule and the collecting duct are not permeable to water . In the prescence of ADH distal convoluted tubule and the collecting duct become permeable to water resulting reabsorption The water reabsorption induced by ADH is called facultative reabsorption of water .

35 Role of kidney in acid-base balance
Kidneys play important role in maintenance of acid- base balance by: excreting hydrogen ions retaining bicarbonate ions. Normally urine is acidic in nature with pH of 4.5 to 6 The metabolic activities in the body produce lot of acids (with hydrogen ions) which threaten to push the body towards acidosis . Kidney prevent this by excreting hydrogen ions and conserving bicarbonate ions.

36 micturition Filling of urinary bladder: cystometrogram Definition
Is a process by which urine is voided from the urinary bladder it is a reflex process Filling of urinary bladder: A reasonable volume of urine can be stored in urinary bladder without any discomfort and without much increase in pressure inside the bladder It is due to the adaptation of detrusor muscle The relationship between the volume of urine and pressure in urinary bladder is studied by cystometrogram cystometrogram Defintion : Cystometrogram is the graphical registration of pressure change in urinary bladder in relation to volume of urine collected in it .

37 Micturition reflex It is the reflex by which Micturition occurs
This reflex is elicited by the stimulation of stretch receptors situated on the wall of urinary bladder and urethra. When about 300 to 400ml of urine is collected in the bladder the pressure inside the bladder increases This stretches the wall of bladder resulting in stimulation of stretch receptors and generation of sensory impulses .

38 Thank you

39 MCQ

40 Choose the correct answer:
1- kidney function concerned with homeostasis such as: Maintenence of water balance Maintenence of electrolyte balance Maintenence of acid-base balance All of the above 2- The hormones secreted by the kidney: Erythropoietin Thrombopoietin Rennin 3- the function of renal corpuscle: Secretion of hormones Regulattion of blood pressure Filtration of blood None of the above 4- The hormone which is secreted by juxtaglomerular apparatus is: Renin Antidiuretic hormone Aldosterone hormone calcitonin

41 5- Hormones which regulate GFR are:
Aldosterone Angiotensin II Antidiuretic hormone All of the above 6- the important role of renin-angiotensin system is: Maintenance of water balance Maintenance of body temperature Maintenance of electrolyte balance Maintenance of blood pressure 7- the pressure exerted by plasma proteins in the glomeruli is called: Glomerular capillary pressure Colloidal osmotic pressure Hydrostatic pressure in Bowman`s capsule Systemic blood pressure 8- Important substances for reabsorption are: Water Glucose Sodium

42 9- the most important factor affecting GFR is:
Tubuloglomerular feedback Renal blood flow Constriction of afferent arteriole Sympathetic stimulation 10- mechanism of tubular reabsorption: By active reabsorption By passive reabsorption By endocytosis A and b 11- substances secreted in different segments of renal tubules are: Potassuim Ammonia Hydrogen ions All of the above 12- the final concentration of urine is achieved by: ADH Aldosterone Angiotensin I parothormone

43 13- kidney regulate acid-base balance by:
Excrete hydrogen ions Retaining bicarbonate ions Retaining hydrogen ions A and b Fill in the bLank: The structural and functional unit of kidney is ………………… which is formed by two parts:1- …………… 2-……………… Nephrons are classified into two types:1-…………… 2-………………. Kidney secrete …………….. which important for erythropoiesis and ………………. for production of thrompocytes. The mechanism of urine formation includes three processes: 1-……….……………………2-…..………………….. 3-………………………… Renal blood flow is regulated by ………………….. which involve two mechanisms:1-…………………………………… 2- ……………………………….. Glomerular filteration rate(GFR) is defined as …………………… . ……………..Normal GFR is ……………………. The final concentration of urine is achieved by ………………….. homrone kidney maintains acid-base balance by……………………… and…………………


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