Hemostasis is the process of forming clots in damaged blood vessels to prevent blood loss while maintaining a fluid state in the vascular system. It involves several stages: vascular constriction, platelet plug formation, coagulation, clot retraction, and fibrinolysis. The process ultimately leads to the dissolution of the clot through fibroblast invasion and tissue organization.

3. Contents
Hemostasis( 1
Vascular Phase( 2
Platelet Phase( 3
Clot formation( 4
Clot retraction( 5
Fibrinolysis( 6

5. Hemostasis

6. Hemostasis is process of*
forming clots in walls of
damaged blood vessels and
preventing blood loss, while
maintaining
blood in a fluid state within
vascular
system
Haima + Stasis
Prevent blood
loss

7. Stages of Hemostasis •

8. I. VASCULAR CONSTRICTION
Immediately blood ( 1 •
vessel is cut or ruptured.
2( Stimulus of trauma to
vessel causes wall of
.
vessel to contract
•
This immediately( 3
reduces the flow of blood
.from vessel rupture

9. More a vessel( 4
is traumatized.
5(
The greater the
degree of
spasm.
6( This local
vascular spasm
can last for
many minutes or
even hours

10. Vascular Phase

11. II. FORMATION OF
THE PLATELET PLUG
When platelets come in contact with
a damaged vascular surface,
they immediately change their
:
characteristics
Begin to swell( 1
Assume irregular forms with ( 2
numerous irradiating
pseudopods protruding from
;their surfaces

12. Their contractile proteins ( 3
contract and cause release of
granules contain multiple active
;
factors
They become sticky so that(4
;they stick to collagen fibers
•

15. III. BLOOD COAGULATION IN
THE RUPTURED VESSEL
Clot begins to develop in 15 to( 1 •
20 seconds if trauma of vascular
wall severe
2(And in 1 to 2 minutes if the
trauma minor
3( Activator substances both from
traumatized vascular wall and
from platelets and blood proteins
adhering to traumatized vascular
..wall initiate clotting process

16. Within 3 to 6( 4
minutes after rupture
of a vessel, if vessel
opening is not too
large, entire opening
or broken end of
vessel is filled with
.clot
After 20 minutes to( 5
an hour, clot retracts;
.this closes vessel

17. CLOT
CLOT is composed of meshwork of fibrin fibers( 1 •
running in all directions and entrapping blood cells,
.
platelets, and plasma
Fibrin fibers also adhere to damaged surfaces of( 2
blood vessels; therefore, the blood clot becomes
adherent to any vascular opening and thereby
.prevents blood loss
•

18. Coagulation process
When tissues( 1
are exposed
enzyme thrombin
.is released
Thrombin( 2
activates clotting
factor in platelets
causing them to
.become sticky

19. Coagulation Process
The platelets begin( 3
to stick together at
wound site binding
.to exposed fibers
Platelets release( 4
several chemicals
and change their
shape to fit
.formation of plug
.

20. Then, a fibrin mesh forms( 5
and insures the clot will
. stay
Finally, blood clot must( 6
dissolve in order to restore
normal blood flow to the
vessel

23. CLOT RETRACTION
Platelets are become attached to fibrin, fibers in( 1
such a way that they actually bond different fibers
.together
Platelets release procoagulant substances, one of (2
which is fibrin-stabilizing factor, which causes more
and more cross-linking bonds between adjacent
.fibrin fibers
Platelets themselves contribute directly to clot( 3
contraction by activating platelet thrombosthenin,
actin, and myosin molecules (contractile proteins(
and cause strong contraction of the platelet attached
.to the fibrin
•
•
•

24. This helps compress fibrin( 4 •
meshwork into a smaller mass.
5( Contraction is activated or
accelerated by thrombin as well as by
. calcium ions released from platelets
As clot retracts,edges of broken( 6 •
blood vessel are pulled together, thus
contributing to ultimate state of
haemostasis

25. Fibrinolysis
Process wherein a fibrin clot, product of
coagulation, is broken down.
Its main enzyme plasmin cuts fibrin mesh
at various places, leading to production of
circulating fragments
That are cleared by other proteases or by
the kidney and liver
HEMOSTASIS

26. FIBROUS ORGANIZATION
((DISSOLUTION OF THE CLOT
It can become invaded by fibroblasts, which ( 1
subsequently form connective tissue all through
.
clot
. it can dissolve( 2
The usual course for a clot that forms in a small hole
of a vessel wall is invasion by fibroblasts, beginning
within a few hours after clot is formed.
This
continues to complete organization of the clot into
.fibrous tissue within about 1 to 2 weeks
•

27. When additional blood
coagulates to form a larger clot
such as blood that has leaked
into tissues, special
substances within the clot itself
usually become activated
And these then
function as enzymes to
.dissolve the clot

29. How does the blood clotting process work_ - DnaTube.com - Scientific Video and Animation Site.flv

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