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Urinary SystemUrinary SystemDr. ZHANG Xiong
Dept. of Physiology
ZJU School of Medicine
Http://10.10.10.151/Able.Acc2.Web/Template/View.aspx?actionp p p
=view&courseType=0&courseId=26519
QUESTION 1QUESTION 1
What is the main function ofWhat is the main function of urinary system?urinary system?
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Structure and Function of Urinary System
QUESTION 2QUESTION 2
What organ is the major organ in urinary system? And Why?
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Acid-base balance
Q ti 3Question 3
How do the kidneys produce the urine?
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Structure of kidney
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N hNephron
Renal corpuscle- Glomerulus- Bowman’s capsule- Bowman s capsule
Renal tubular systemProximal tubuleLoop of HenleLoop of Henle- Decending thick limb
di hi li b- Decending thin limb- Ascending thin limbg- Ascending thick limbDi t l l t d t b lDistal convoluted tubuleCollecting duct systemg y
Play theBasic Renal Processes
The basic renal processes of urine formation:The basic renal processes of urine formation:1. Glomerular filtration of plasma2. Tubular Reabsorption of filtrate3. Tubular Secretion of filtrate3. Tubular Secretion of filtrate4. Dilution or Concentration of filtrate
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QUESTION 4QUESTION 4
How is the plasma filtered in glomerulus?1. What structure permits the plasma filtering
through glomerular capillaries?
2. What force determines the plasma filtering th h l l ill i ?through glomerular capillaries?
Glomerulus and Bowman’s capsule -G om ru us an owman s capsu site of filtration
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Structure of glomerulusStructure of glomerulus
Podocyte and slit diaphragmCapillary endothelium with pores(25-50 nm)( 5 50 )
Pod
Bas
En d
Filtration barrier
ocytes
ement
dotheli st mem
b
ia cell branel
layer
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Factors determining passage of moleculesFactors determining passage of molecules through the filtration barrierthrough the filtration barrier
1. Size of pores -- Mechanical barrier. S e o po es ec c b e
2. Negative charges – Charge barrier
Blood cells and proteins NOT filtered.
Presence of proteins and blood cells in urine indicates impairment of glomerulus.
Formation of the glomerular filtrate in Bowman’sFormation of the glomerular filtrate in Bowman s capsule is the outcome of opposing pressures. p pp g p
1 Gl l1. Glomerularhydrostatic pressurehydrostatic pressure favors filtration.
2. Colloid Osmotic and h d t tihydrostatic pressure of the filtrate inof the filtrate in Bowman’s capsule
ioppose it.S li di dSome liver diseases and kidney diseases;Obstructive abnormalities
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As vasodilation and vasoconstriction of the afferent and efferent arterioles alter the blood flow through the glomerular capillariesarterioles alter the blood flow through the glomerular capillaries, there are corresponding alterations in the glomerular filtration
(G )rate (GFR).
QUESTION 5QUESTION 5
What change will happened to GFR when renal blood pressure changed?
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Evaluation for Glomerular filtration
Glomerular filtration rate (GFR)Glomerular filtration rate (GFR)
The quantity of the glomerular filtrate produced by allThe quantity of the glomerular filtrate produced by all nephrons of the both kidneys in each minute.p y
Normal value = 125 ml / min
Filtration fraction (FF)Filtration fraction (FF)
FF = GFR / Renal plasma flow per minuteFF GFR / Renal plasma flow per minute
Autoregulation of gRBF and GFR
1. Myogenic theoryy g y
2 Flow dependent 2. Flow dependent mechanism (Tubulo-glomerularfeedback)feedback)
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hMyogenic Theory
Arterial blood pressure↑
Resistance of arterioles ↑due to Resistance of arterioles ↑due to smooth muscle contraction in response to stretch
Blood flow not changedg
T b l l l f db kTubulo-glomerular feedback
juxtaglomerular apparatus
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Functional importance of autoregulation ofFunctional importance of autoregulation of RBF and GFRRBF and GFR
1 C t i bl d f i t th kid &1. Constancy in blood perfusion to the kidney & maintenance of blood volume in the systemicmaintenance of blood volume in the systemic circulation
2. Constancy of GFR – prevent excessive loss of water and electrolytes
Normally GFR = 120 ml/min UF = 1 ml/minNormally, GFR = 120 ml/min UF = 1 ml/min
R fReferences
1 Guyton and Hall1. Guyton and HallTextbook of Medical Physiology 10th Edition y gy
2 D M d P l2. Datta, Mirpuri and PatelCrash Course Renal and urinary Systems 2nd editionCrash Course Renal and urinary Systems, 2nd edition
3. Vander’s Human Physiologyh10th Edition