Urinary system rids the body of waste materials and control the volume and composition of

Urinary system rids the body of

waste materials and control the

volume and composition of

body fluids

body fluids

Fungsi Ginjal

1. Ekskresi/Pembentukan Urine
Mempertahankan homeostasis

 Mengatur osmolalitas ECF  Mengatur volume ECF

2. Endokrin/Hormon (Non Ekskresi)

Menghasilkan renin
mengatur TD

Menghasilkan erythropoeitin
stimulasi

eritropoeisis oleh sumsum tulang

Mengaktifkan vitamin D
absorbsi Ca dalam

usus dipermudah

Menghasilkan prostaglandin

Blood supply of the kidney:

21% of the cardiac output =

1200 ml/mnt

Formation of Urine

Involves three main processes:

1.Filtration

2.Reabsorption
3.Secretion

Nephron

Merupakan unit fungsional ginjal
1 ginjal terdapat ± 1,2 juta nephron

Berdasarkan lokasi dibedakan atas 2 yi

cortical dan juxtamedullary nephron cortical dan juxtamedullary nephron

Struktur nephron terbagi atas :

Glomerulus dan,

Tubulus renalis; tubulus proximal, loop of

Henle & tubulus distal serta collecting duct

Arcuate artery

Arcuate vein Distal convoluted tubule

Proximal convoluted tubule

Collecting duct Vascular supply to the nephron

Glomerulus Afferent arteriole

Efferent arteriole

Thin ascending limb of the loop of Henlé Thick ascending limb of the loop of Henlé

Collecting duct

Descending limb loop of Henlé Vasa recta

Cortical & Juxtamedullary

nephron

Cortical Nephron

Glomerulus terletak 2/3

bagian luar cortex

85% dari seluruh

nephron

Juxtamedullary Nephron

Terletak bagian dalam

cortex dekat medulla

15% dari seluruh

nephron nephron

Loop of henle pendek

Dikelilingi oleh kapiler

peritubular berbentuk jala  network

nephron

Loop of henle panjang,

lebih dalam masuk ke medulla

Dikelilingi kapiler

berbentuk U  vasa recta

Capsule space Afferent arteriole Juxtaglomerular cell Parietal layer of glomerular capsule

Structure of the Bowman’s (glomerular) capsule

Proximal convoluted tubule space Efferent arteriole Pedicel Podocyte Endothelium of glomerulus

Filtration membrane

Is composed of three layers:

1. fenestrated glomerular endothelium 2.basement membrane

filtration slits are formed by the pedicels

3.filtration slits are formed by the pedicels

of the podocytes

Substance are filtered are on the basis of size and/or electrical properties

Glomerular Filtration Membrane

Glomerular Filtration Membrane

Endothelial capillary pores are large

fenestrae.

100-400 times more permeable to

plasma, H 0, and dissolved solutes than plasma, H₂0, and dissolved solutes than capillaries of skeletal muscles.

Pores are small enough to prevent

RBCs, platelets, and WBCs from passing through the pores.

Glomerular Filtration Membrane

Filtrate must pass through the basement

membrane:

 Thin glycoprotein layer.  Negatively charged.

Podocytes:

 Foot pedicels form small filtration slits.

The filtration barrier - podocytes fenestrated endothelium pedicel filtration slit basal lamina fenestrated endothelium primary process podocyte cell body secondary process (pedicel) filtration slit basal lamina podocyte

The filtration barrier - pedicels Bowman’s space pedicel filtration slit capillary slit

Common component of the glomerular filtrate:

Organic molecules: glucose,amino

acids

Nitrogenous waste: urea, uric acid,

creatinine

Forces affecting filtration

Glomerular hydrostatic pressure (blood

pressure) promotes filtration=55 mmHg

Capsular hydrostatic pressure opposes

filtration=15 mmHg

Glomerular osmotic pressure opposes
Glomerular osmotic pressure opposes

filtration=30 mmHg

Net filtration pressure =

GAYA FISIK YANG TERLIBAT DALAM FILTRASI GLOMERULUS

1. Tekanan darah kapiler

gomerulus (P_GC) = 55 mmHg 2. Tekanan osmotik koloid

plasma (II_GS) = 30 mmHg 3. Tekanan hidrostatik kapsul

P_C P_I Π Π Π ΠI ΠΠΠΠC

3. Tekanan hidrostatik kapsul Bowman (P_BC) = 15 mmHg

Tekanan filtrasi netto : = P_GC – (II_GS – P_BC) = 55 - (30+15) = 10 mmHg P_GC P_BC Π Π Π ΠGS

Glomerular filtration rate

The total amount of filtrate formed by the kidney per minutes

Sekitar 20% dari renal plasma flow

Nilai GFR ditentukan oleh: (1) keseimbangan

antara tekanan hidrostatis dan osmotik (2) filtration coefficient kapiler (Kf) yaitu

permeabilitas dan area permukaan filtrasi

Qualities of agents to measure GFR

Inulin: (Polysaccharide from Dahalia plant)

 Freely filterable at glomerulus

 Does not bind to plasma proteins  Biologically inert

 Non-toxic, neither synthesized nor metabolized in

kidney kidney

 Neither absorbed nor secreted  Does not alter renal function  Can be accurately quantified

Creatinine:

 End product of muscle creatine metabolism

 Used in clinical setting to measure GFR but less

accurate than inulin method

 Small amount secrete from the tubule

Para-aminohippurate (PAH):

 An organic anion not present in body  An organic anion not present in body

 Freely filtered, secreted but not reabsorbed by

nephron

 Non-toxic, neither synthesized nor metabolized

in kidney

Solute Clearance:

Rate of removal from the Blood

Concept of clearance

Where,

Cx = Clearance of substance X (mg/min)

Ux = Urine concentration of X (mg/ml)

Px = Plasma concentration of X (mg/ml)

V = Urine flow rate of X (ml/min)

GFR = Cx =

Px

Ux . V

Qx extracted = Qx excreted Px . Cx = Ux . V

Effective renal plasma flow =GFR Effective renal plasma flow =GFR

ERBF = Cx =

1 - Hct ERPF

Renal blood flow = RBF = _{Extraction ratio}

ERBF

Effective renal blood flow =

Extraction ratio (0.9) = _A PAH

A_PAH - V_PAH

Hct=hematocrit

V_PAH = vein plasma PAH A_PAH = arterial plasma PAH

Cara pengukuran LFG dengan

metode clearance

Inulin clearance merupakan suatu

polisakarida dgn BM 5200, bersifat

mengalami filtrasi dan tidak mengalami reabsorpsi dan sekresi sehingga

reabsorpsi dan sekresi sehingga didapat:

U.V_inulin = GFR.P_inulin

Clearance Creatinine, merupakan hasil

metabolisme otot dan dikeluarkan dari tubuh melalui proses filtrasi

Creatinine Cleareance =

U .V / P

U_creatinine.V_creatinine / P_creatinine

Clearance PAH = Renal Plasma Flow ok PAH

mengalami proses sekresi seluruhnya sehingga yang dijumpai di plasma akan sama dengan

yang diekskresikan

Juxtaglomerular apparatus

As the thick ascending loop of henle transition

into early distal tubule, the tubule runs adjacent to the afferent and efferent arteriole.

Where these structure are contact they form the

Where these structure are contact they form the

monitoring structure called the juxtaglomerular apparatus (JGA), which is composed macula densa and JG cells

JG monitor the blood pressure within the

arteriole (baroreceptor),

Macula densa; monitor and respond to

changes of the osmolarity of the filtrat in changes of the osmolarity of the filtrat in the tubule

Regulation of GFR

Autoregulation Mechanism

To counteract changes in GFR 1. Myogenic mechanism

Increased systemic pressure: Autoregulation:

afferent arteriole diameter decreased (constricted) afferent arteriole diameter decreased (constricted) to maintain the GFR

Decreased systemic pressure: Autoregulation:

afferent arteriole diameter increased (dilated) to maintain the GFR

Autoregulation Mechanism

2. Tubuloglomerular mechanism:

the sensitivitiy of the macula densa cells of juxtaglomerular apparatus to the filtrate

osmolarity and/or rate of filtrate flow in the osmolarity and/or rate of filtrate flow in the

High osmolarity: macula densa release the

vasonconstrictor that effects: afferent arteriole constricts

GFR decrease

 GFR decrease

 Tubular filtrate flow slows

Low osmolarity: macula densa cells: release less

vasonconstrictor afferent arteriole dilated, signal to the juxtaglomerular cells to release Renin.

JG cells also sense to the very low blood JG cells also sense to the very low blood

pressure directly and release renin in response

Renin release triggers production of Angiotensin

II

Angiotensin causes : efferent arteriole diameter

↓, blood flow out of glomerulus ↓, glomerular hydrostatic pressure ↑, GFR ↑

Sympathetic control

In extreme stress or blood loss, sympathetic stimulation overrides the autoregulation

Increased sympathetic discharge cause intense

constriction of renal blood vessel constriction of renal blood vessel

Blood is shunted to other vital organs

GFR reduction causes minimal fluid loss from

Reduction filtration can not go indefinitely, a

waste product build up & metabolic imbalances increase in blood

IV fluid increases blood volume  restores blood IV fluid increases blood volume  restores blood

pressure to resting levels  reduced sympathetic stimulation allows for normal arteriole diameter  GFR & filtrate flow is normalized

Sympathetic Regulation of GFR