C8 FORMATION OF URINE BY THE KIDNEY

Today I am going to introduce: 1.the microstructure of the Kidney 2. glomerular filtration

our goals are ⑴ understand microstructure of the kidney ⑵ understand the characteristic of blood circulation in the kidney ⑶ describe glomerular filtration

Functions of The kidney: ⑴ regulate water and inorganic ion equilibrium.maintain constant of internal environment regulate the osmotic pressure of body fluids; the osmotic pressure is formed by electrolyte, kidney regulate value of electrolyte, acid and base excretion, and then regulate the osmotic pressure, the electrolyte equilibrium and adjust the balance of acid and base in body fluids.

⑵ excrete metabolic waste end-products into the urine ; NH3 some poisons

⑶ excrete foreign chemicals drugs metabolites ⑷ gluconeogenesis synthesize glucose from amino acids. ⑸ endocrine function secrete erythropoietin, renin,

Which is main function of the kidney? excrete urine produce urine Store urine Transport urine

Which is main function of the ureter ? excrete urine produce urine Store urine Transport urine

Mechanisms of urine formation : (1) Filtration (2) Secretion (3) Reabsorption

Structure of the kidneys and urinary system

cortex medulla

The Nephron and collecting Duct 2,000,000 nephrons Functional unit of kidney

① composition of nephron loop of Henle; nephron renal corpuscle glomerulus Bowman’s capsule renal tubule proximal convoluted tubule distal convoluted tubule The collecting duct

What is functional unit of the kidney? nephron glomerulus renal tubule collecting duct

② types of nephron (1)cortical nephrons: (85% )1)cortical nephrons In the outer and middle portion of the renal cortex (shorter loops)

cortical nephrons juxtamedullary nephrons loop of Henle Collecting duct

② types of nephron (2) juxtamedullary nephrons : (15% ) In the inner cortex (longer loops)

cortical nephrons juxtamedullary nephrons loop of Henle Collecting duct

Juxtaglomerular Apparatus (1)the juxtaglomerular cells: they are specialized myoepithelial cells in afferent arteriole release renin

(2)the macula densa : monitor the concentration of NaCl in the tubular fluid and transfer the information to juxtaglomerular cells

What is cell of release renin? juxtaglomerular cells extraglomerul ar mesangial cell macula densa

What is cell of monitor the concentration of NaCl in the tubular fluid? juxtaglomerular cells extraglomerul ar mesangial cell macula densa

1.The endothelial layer of the capillary 2.The basement membrane 3.The epithelial cell layer of Bowman’s capsule Glomerular Membrane physical barrier

special structure Fenestra: prevent the filtration of all particles with an average size greater than 16 millimicron. Red cell

Meshwork (basement membrane of the capillary) proteoglycan prevents the filtration of all particles with diameter greater than 11 millimicron

Slit-pores

prevent the filtration of all particles with diameter greater than 7 millimicron. (diameter of plasma proteins ﹥ 7 millimicron) plasma proteins

Electrical barrier Glycoprotein (negatvely charge)

prevent filtration of negatively charged plasma proteins

﹤ 2 nm( millimicron) –can be filtered easily ﹥ 4.2 nm--can not be filtered between---can be filtered proportionately Anionic substances: difficult to be filtered (albumin) Neutral substances:

The glomerular membrane is almost completely impermeable to all cells and plasma proteins but is highly permeable to all dissolved substances(such as electrolyte, glucose )

In following substance, What substance is not filter through the glomerular membrane. plasma protein water ions electrolyte glucose

Innervation of the renal vessels Sympathetic fiber Sympathetic nerve cause constriction of renal blood vessels, which greatly decreases blood flow to the kidney.

renal artery → afferent arteriole → glomerular capillaries → efferent arteriole → peritubular capillaries → renal vein Renal Blood Flow and Regulation

(1)glomerular capillary bed : high pressure → filtering continually out of the glomerulus into Bowman’s capsule Two capillary beds

(2)peritubular capillary bed : low pressure → fluid being reabsorbed continually into the capillaries

What is characteristic of the glomerular capillary bed? low pressure high pressure

What is characteristic of the peritubular capillary bed? low pressure high pressure

① renal blood flow is about 1200ml/minute ② The renal fraction is about 21 per cent (1)Renal Blood Flow

③ About 94 per cent of renal blood flow goes to the renal cortex.

(2) Autoregulation of Renal Blood Flow When BP changes from 80 to 180 mmHg, a relatively constant renal blood flow is maintained.

mechanism * When BP descends, afferent arteriole relax and decrease resistance of afferent arteriole, and then the renal blood flow does not change. * When BP rises, afferent arteriole contract and increase resistance of afferent arteriole, and then the renal blood flow does not change, too

(3)Neuro-Humoral Control Sympathetic nerve: → constriction of renal blood vessels → decreases blood flow Vasoconstrictor agents : Angiotensin II epinephrine and norepinephrine Vasodilator agents : bradykinin, NO and some prostaglandins

plasma → Bowman’s capsule → proximal convoluted tubule → loop of Henle → distal convoluted tubule → collecting duct → papilla → renal alyces

when blood passes through the glomerulus, plasma component (water, ions, and small molecules filter into Bowman's capsule. Glomerular Filtration

2-2. Filtration Pressure ① capillary pressure (causes filtration ) ② colloid osmotic pressure in the blood (oppose filtration) ③ capsular pressure in Bowman’s capsule (oppose filtration)

afferent arterioleefferent arteriole The effective filtration pressure(EFP) ③ capsular pressure ② glomerular colloid osmotic pressure ① the glomerular pressure EFP = ① - ( ② + ③）

① the glomerular pressure : 45 mmHg. ② colloid osmotic pressure in the blood increase from 25 to 35 mmHg. ③ capsular pressure: 10 mmHg 45mmHg 10mmHg 25-35mmHg

45mmHg 10mmHg 25-35mmHg (1) afferent side : EFP=45-(25+10)=10mmHg filter (2) efferent side : EFP=45-(35+10)= 0mmHg filter stop

2-3.Glomerular Filtration Rate (GFR) The quantity of glomerular filtrate formed each minute in all nephrons of both kidneys. (normal:125 ml/min) 180 L/d 99 % reabsorbed 1 % excreted as urine

filtration fraction The ratio that GFR and renal plasma flow. GFR=125ml/min renal plasma flow =660ml/min Filtration fraction =125/660=19%

filtration coefficient (K f ) It image the condition of the area and permeability of glomerular membrane. a constant in nomal change in kidney disease GFR= Filtration pressure K f

2-4. determinants of the glomerular fitration rate GFR= Filtration pressure Kf

Because of autoregulation, 80 mmHg ~ 180 mmHg. the glomerular filtration rate is constant (1) Effect of Glomerular Capillary Pressure BP ↑ (over 180mmHg) → glomerular capillary pressure ↑ → effective filtration pressure ↑ → GFR ↑

Liver function ↓ or proteinuria → plasma colloid osmotic pressure ↓ → effective filtration pressure ↑ → GFR ↑ (2) Effect of the Plasma Colloid Osmotic pressure

ureter occlusion caused by ureteral calculus, cancer etc. → Capsular Pressure ↑ → effective filtration pressure → GFR (3) Effect of Bowman’s capsule Pressure

③ capsular pressure ② glomerular colloid osmotic pressure ① the glomerular pressure EFP = ① - ( ② + ③） (4) Effect of Renal Blood Flow Effect of Renal Blood Flow renal blood flow ↑ → plasma colloid osmotic pressure rises slowly → GFR ↑

renal plasma flow renal blood flow plasma colloid osmotic pressure rises fastly flitrate Concentration of plasma protein% Concentration of plasma protein in normal

renal blood flow in normal the glomerular pressure glomerular colloid osmotic pressure capsular pressure length

renal blood flow the glomerular pressure glomerula r colloid osmotic pressure capsular pressure length

renal blood flow the glomerular pressure Glomerul ar colloid osmotic pressure capsular pressure length

(1)K f : the area and permeability of glomerular membrane Permeability ↑→ Hematuria, proteinuria the area → urine in chronic nephritis (5)Glomerular capillary filtration coefficient

We have studied: 1. the anatomy construction of the kidney 2. the characteristic of blood circulation in the kidney 3. glomerular filtration

Please answer the questions 1.Explain physiology word: Glomerular Filtration Rate filtration fraction 2. What is functional unit of the kidney? 3. What is composition of nephron 4. What are characteristic of the glomerular capillary bed and peritubular capillary bed 5. The effective filtration pressure 6.Factors Affecting GFR