Haemostasis dr Sri Lestari - PowerPoint Presentation

Slide1

Haemostasis

dr

Sri Lestari

Sulistyo

Rini

,

MSc

Slide2

Five Stages of Hemostasis

Vessel spasm

Formation of the platelet plug

Blood coagulation or development of an insoluble fibrin

clot

Clot retraction

Clot dissolution

Slide3

Figure 19–11a

The Vascular Phase

A cut triggers

vascular spasm

30-minute contraction

Slide4

3 Steps of the Vascular Phase

Endothelial cells contract:

expose basal lamina to

bloodstream

Endothelial cells release:

chemical factors: ADP, tissue factor,

prostacyclin

local hormones:

endothelins

stimulate smooth muscle contraction and cell division

Endothelial cell membranes become “sticky”:

seal off blood flow

Slide5

Functions of Thrombin

Stimulates formation of tissue factor

stimulates release of PF-3:

forms positive feedback loop (intrinsic and extrinsic):

accelerates clotting

Slide6

The Platelet Phase

Begins within 15 seconds after injury

Figure 19–11b

Slide7

Platelets

Small fragments of megakaryocytes

Formation is regulated by thrombopoietin

Blue-staining outer region, purple granules

Granules contain serotonin, Ca

2+, enzymes, ADP, and platelet-derived growth factor (PDGF)

Slide8

Roles of Vessel Endothelial Cells in Physiological

Hemostasis

Roles are close related to its endocrine functions

Vessel endothelium serves as barrier between

underendothelial

structure (namely, collagen) and blood. As soon as collagen expose to blood,

hemostasis

of platelet is immediately activated to form thrombus blocking wounded vessels

.

Slide9

Platelet activation can releases constrictive factors (TXA

2

, ET-1, 5-HT, etc) making vessel convulsion, lasting about 60 sec.

Stimulated vessel endothelial cells release

coagulative

factors and Promoting

coagulative

material to realize, speed up blood coagulation. At the same time, cells also release

anticoagulative

factors and

fibrinolysis

material to modify blood coagulation.

Slide10

Endocrine

functions of vessel endothelial cells

Material related to

hemostasis

are basal membrane, collagen (III, IV),

microfibril

,

elastin

,

laminin

,

ectonectin

,

fibronectin

, von

Willebrand

factor (

vWF

), protein enzyme, protein enzyme inhibitor, adhesive

amylose

, etc.

Anticoagulative

material: They are

prostacyclin

(PGI

2

), endothelium-derived relaxing factor (EDRF or nitric oxide, NO), tissue-type

plasminogen

activator (

tPA

),

uPA

,

ADPase

, ATIII, heparin sulfate, protein C,

thrombomomodulin

(TM),

plasminogen

activator (PA

).

Slide11

Promoting

coagulative

material: Tissue factor,

vWF

, blood clotting factor V,

plasminogen activator inhibitor (PAI-1, PAI-2, ATIII), TNF

α, interleukin-1 (IL-1).

Vessel constricting and relaxing modulators: endothelin-1 (ET-1), EDRF (NO), PGI

2

, etc.

Endocrine

functions of vessel endothelial cells

Slide12

Platelet

Normal value:

100×10

9

~ 300×10

9

, range from 6%~10%

Normal changes

:

more number in the afternoon than in the morning, more in winter than in spring, more in the venous blood than capillary, after sport↑,

pregnacy

↑.

Slide13

Life- Span and Breakage of Platelet

Life-span:

Averagely, 7~14 days in the blood. It can be consumed when it displays physiological functions.

Breakage:

Aged platelet can be processed by

phagocytosis

in liver, spleen and lymphatic node.

Slide14

Function of Platelet

Functions

:

1

.

It maintains capillary endothelial cells smooth

and integrated (repairing endothelium and providing

nutrition).

2. It is involved in physiological

hemostasis

.

Platelet and clinic relation

:

decrease of platelet, abnormal immune reaction, will results in hemorrhage or bleeding,

purpuric

symptom.

Slide15

Platelets

Form a temporary platelet plug that helps seal breaks in blood vessels

Circulating platelets are kept inactive and mobile by NO and

prostacyclin

from endothelial cells of blood vessels

Slide16

Physiological

Characteristics of Platelet

Thrombocyte

adhesion:

its membrane glycoprotein (GP,

GPIb

/IX

and

GPIIa

/

IIIb

), collagen (

underendothelial

structure),

vWF

(plasma component),

fibrinogen are involved in adhesion.

Mechanism

: Exposed

collagen +

vWF

→

vWF

changes

→ platelet

membrane

glycoprotein + changed

vWF

→

Thrombocyte

adhesion.

Slide17

Thrombocyte

aggregation

:

induced by physiological factors such as

ADP

,

thromboxane

A

2

(TXA

2

),

epinephrine, 5-HT, histamine, collagen, thrombin,

prostacyclin,etc

and by pathological factors like bacteria, virus, immune complex, drugs, etc.

Slide18

The process can be separated into two phases: phase one is reversible aggregation and phase two irreversible aggregation. Two phases require Ca

2+

, fibrinogen and energy consumption

Mechanism

:

Various factors+corresponding

receptors on the platelet

→changes in the second

messenger within platelet

→

cAMP

↓, Ip

3

↑, Ca

2+

↑,

cGMP

↑→ platelet

aggregation

.

Slide19

Thrombocyte

release:

ADP, ATP, 5-HT, Ca

2+

released from dense body, and

β

-platelet

globin

, PF

4

,

vWF

, fibrinogen, PFV, PDGF, thrombin sensitive protein from

α

-granule, and acid protein

hydrolyzed enzyme, tissue hydrolyzed enzyme from

lysosome

.

Slide20

Thrombocyte

contraction:

Loose platelet thrombus could turn into compact platelet thrombus by

Ca

2+

release and

cytoskeleton movement (filament/

canaliculus

)

within platelet.

Slide21

Inactive Platelet

Under the electronic microscope

Slide22

Activated Platelet for Hemostasis

Under the electronic microscope

Slide23

Roles of Platelet in

Hemostasis

1.

Activated platelets supply

lecithoid

(

phospholipid

) surface for blood clotting factor and involve in activating factor X and

prothrombin

.

2.

Surface of platelet membrane combine with many blood clotting factor, such as fibrinogen, FV, FXI, FXIII to speed up coagulation.

Slide24

3

.

Activated platelets release

α

-granule which contains fibrinogen to intensify fibrin forming and blood coagulation.

4.

Activated platelets contract clot with its contractive protein to solidify blood coagulation.

Roles of Platelet in

Hemostasis

Slide25

Mechanism of

Platelet in

Hemostasis

Slide26

Mechanism

of Platelet in

Hemostasis

Slide27

Activated Platelets

Release Clotting Compounds

Adenosine

diphosphate

(ADP)

Thromboxane A

2 and serotonin Clotting factorsPlatelet-derived growth factor (PDGF)

Calcium ions

Slide28

Slide29

Platelet Plug: Size Restriction

Prostacyclin

:

released by endothelial cells

inhibits platelet aggregation

Inhibitory compounds:

released by other white blood cells

Circulating enzymes: break down ADP

Negative (inhibitory) feedback: from serotonin

Development of blood clot: isolates area

Slide30

The Coagulation Phase

Begins 30 seconds or more after the injury

Figure 19–12a

Slide31

Slide32

Blood

Coagulation

Blood Clotting Factor

Definition: The process of blood flow from flowing liquid to

gel

or

gelatin

.

Serum: Light yellow fluid after blood coagulation.

Difference between serum and plasma mainly consists in no fibrinogen in serum.

Blood coagulation is a series of complicated biochemical reactions with various enzymes

.

Slide33

Blood clotting factor: Material which are directly involved in blood coagulation. There are 12 factors named Roman numerals, except Ca

2+

,

phospholipid

，

other factors being protein, and except FIII (TF), others are in fresh plasma synthesized by liver with

VitK

.

Blood clotting enzymes have two type: inactive and activated type [FII, FVII, FIX,

Fx

, FXI, FXII, FXIII].

Slide34

Table 19–4

Slide35

Clotting Factors

Also called

procoagulants

Proteins or ions in plasma

Required for normal clotting

Fibrin networkCovers platelet plugTraps blood cells

Seals off area

Slide36

Cascade Reactions

During coagulation phase

Chain reactions of enzymes and

proenzymes

Form 3

pathways

Slide37

3 Coagulation Pathways

Extrinsic pathway

: 20-30”

begins in the vessel wall

outside blood stream

Intrinsic pathway

: 1-2’begins with circulating

proenzymes

within

bloodstream

Common pathway

:

where intrinsic and extrinsic pathways converge

Slide38

The Extrinsic Pathway

Stimulus activates tissue factor (FIII) as beginning of coagulation.

Damaged

cells release

tissue factor

(TF)

TF + other compounds = enzyme complex

Activates Factor X

Slide39

The Intrinsic Pathway

All blood clotting factors involved in blood coagulation come from blood.

Eyewinker

surface with negative charges (

collagenin

) on the endothelium of blood vessel activates blood FXII as beginning of coagulation named

surface activation

.

Activation

of enzymes by collagen

Platelets release factors (

e.g.,

PF–3

)

Series of reactions activate Factor X

Slide40

The Common Pathway

Enzymes activate Factor X

Forms enzyme

prothrombinase

Converts

prothrombin to

thrombin

Thrombin

converts

fibrinogen

to

fibrin

Slide41

Slide42

Slide43

Intrinsic and Extrinsic Coagulation Pathways

Terminal steps in both pathways are the same:

Calcium, factors X and V, and platelet phosopholipids combine to form prothrombin activator

Prothrombin activator converts prothrombin to thrombin

This interaction causes conversion of fibrinogen in fibrin stands that create the insoluble blood clot

Slide44

Regulation of Blood Coagulation

Antithrombin

III inactivates coagulation factors and neutralizes thrombin

When

antithrombin

III is

complexed

with naturally occurring heparin, its action is accelerated and provides protection against uncontrolled thrombus formation on the endothelial surface

Protein C, a plasma protein, acts as an anticoagulant by inactivating factors V and VIII

Slide45

Humoral

anticoagulative

system

:

1.

Amino acid protease inhibitors in blood include

antithrombin

III

,

Cl

-inhibitor,

α

1 antitrypsin,

α

2

antiplasmin

,

α

2

huge

globin

, heparin coenzyme II, protease nexin-1 (PN-1) to combine with

FIXa

,

FXa

,

FXIa

,

FXIIa

and thrombin and then inactivate them for anticoagulation. Heparin can intensify functions of

antithrombin

III

.

Slide46

2. Protein C system are protein C (PC),

thrombomodulin

(TM), protein S and Protein C inhibitors. Main functions of PC consist in ①It inactivates

FVa

,

FVIIIa with

phospholipid and Ca2+;

②

It blocks

FXa

combining with platelet

phospholipid

membrane to reduce

prothrombin

activation;

③

It stimulates

plasminogen

activators release to trigger

fibrinolysis

; ④

Protein S is a coenzyme of PC and greatly intensify functions of PC.

Slide47

3.

Tissue factor pathway inhibitor (TFPI) mainly coming from vessel endothelial cells inhibits

FXa

and inactivates

FVIIa

-TF complex to block extrinsic pathway of coagulation with negative feed back.

4.

Heparin used in the clinic widely is due to

①

It combines with

antithrombin

III

to increase functions of

antithrombin

III

;

②

It stimulates vessel endothelial cell

greatlu

releasing TFPI and other

anticoagulative

material;

③

It intensifies PC activation and stimulates vessel endothelial cell releasing

plasminogen

activators to increase

fibrinolysis

. [lower molecular weight heparin is less hemorrhage]

Slide48

Slide49

Clotting: Area Restriction

Anticoagulants

(plasma proteins):

antithrombin

-III

alpha-2-macroglobulin

2. Heparin

” is a natural anticoagulant made by

basophils

& mast cells (activates

Antithrombin

III)

3. Protein

C

(activated by

thrombomodulin

)

4.

Prostacyclin

Slide50

Slide51

Fibrinolysis

Slow process of dissolving clot:

thrombin

and

tissue

plasminogen

activator (t-PA)

:

activate

plasminogen

Plasminogen

produces

plasmin

:

digests fibrin strands

Plasmin

breaks down fibrin into fibrin degradation products that act as anticoagulants

Protein S, another plasma protein, accelerates the action of protein C

Slide52

Two fibrinolytic

systems:

cellular one and plasma one. The former is

leucocyte

, macrophage, endothelial cell, mesothelial cell and platelet to engulf and digest fibrin. The latter is

plasminogen activators (PA) and its inhibitors (PAI),

plasminogen

,

plasmin

.

Slide53

Blood Coagulation and

Fibrinolysis

Slide54

Antifibrinolysis

Main

fibrinolytic

inhibitors:

They are

plasminogen

activator inhibitor type-1 (PAI-1, in platelet),

α

2

-antiplasmin (in liver),

α

2

-huge

globin

,

α

1

-antitrypsin,

antithrombin

III,

alexin

C

1

inhibitor.

PAI-1 synthesis and release:

PAI-1 made by endothelial cell, smooth muscular cell,

mesothelial

cell,

megakaryocyte

is stored in platelet with inactive form. Some factors such as thrombin, IL-1, TNF

α

, etc stimulate its release from platelet.

PAI-1 function:

It inhibits

tPA

(tissue-type

plasminogen

activator) limiting local

fibrinolysis

of thrombus.

α

2

-antiplasmin characteristics:

(1) Quick effect, (2) Inhibit

plasminogen

adhering to fibrin; (3) Combine with fibrin

α

chain and block

fibrinolysis

Clinic relation:

Innate deficiency of

α

2

-antiplasmin often brings about serious hemorrhage.

Slide55

Slide56

TERIMA KASIH