2009-5-4

1

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?

2009-5-4

2

Structure and Function of Urinary System

QUESTION 2QUESTION 2

What organ is the major organ in urinary system? And Why?

2009-5-4

3

Acid-base balance

Q ti 3Question 3

How do the kidneys produce the urine?

2009-5-4

4

Structure of kidney

2009-5-4

5

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

2009-5-4

6

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

2009-5-4

7

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

2009-5-4

8

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

2009-5-4

9

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?

2009-5-4

10

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)

2009-5-4

11

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

2009-5-4

12

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