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Renal system

Renal system. 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

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Renal system

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  1. Renal system

  2. function of the kidney

  3. Formation of urine . • 1- Role in homeostasis: • Primary function of kidneys is homeostasis such as : • Excretion of waste products • Urea,Uricacid,CreatinineandBilirubin 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 function of the kidney :

  4. 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. function of the kidney :

  5. NEPHRON

  6. It is structural and functional unit of kidney. • Types of nephron: 1- cortical nephron: in outer cortex 2- juxtamedullarynephron: 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 Nephron

  7. Structure of Renal corpuscleTwo 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

  8. 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)

  9. 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

  10. Renin- angiotensin system • Renin released into the blood • Angiotensinogenreninangiotensin 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

  11. 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 Renal circulation

  12. URINE FORMATION

  13. 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(1000-1500ml) of urine is formed every day • The mechanism of urine formation includes three processes : • Glomerular filtration • Tubular reabsorption • Tubular secretion Urine formation

  14. Mechanism of Urine formation I-Glomerularfilteration: • 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

  15. 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

  16. 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.

  17. 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)

  18. II- Tubular 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:

  19. 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 • Angiotensinll • 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

  20. Reabsorption of important substances: • sodium: 99% reabsorbed • water: • from proximal convoluted tubule (PCT): obligatory water reabsortption • fromdistal 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

  21. 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

  22. Concentration & Dilution of urine

  23. 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 1200 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

  24. 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

  25. 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 .

  26. 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.

  27. micturition • 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 .

  28. 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 .

  29. Thank you

  30. MCQ

  31. 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 • All of the above 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 juxtaglomerularapparatus is: • Renin • Antidiuretic hormone • Aldosterone hormone • calcitonin

  32. 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 • All of the above

  33. 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

  34. 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-……………………………….. • Glomerularfilteration 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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