This document provides an introduction to haemostasis by Dr. Ibrahim Khider. It defines haemostasis as the process of stopping blood flow following injury to a blood vessel. There are three components involved - the extravascular tissues, blood vessels, and intravascular platelets and plasma proteins. Haemostasis occurs through primary, secondary, and tertiary processes. Primary haemostasis involves platelets forming a platelet plug at the site of injury within 3-5 minutes. Secondary haemostasis reinforces this plug with a fibrin clot formed from plasma coagulation factors, taking 5-10 minutes. Tertiary haemostasis involves fibrinolysis to remove the clot as healing occurs over 48-72 hours.

1. Introduction to
Haemostasis
• Dr.Ibrahim Khider
• Assistant Professor of
Haematology
• Al Neelain University
Dr.Ibrahim Khider

2. HaemostasisHaemostasis
 The word “Haemostasis” is
derived from Greek word
meaning the stoppage of blood
flow.
 Haem= blood
 Stasis= making something
motionless
 Previously it was understoodDr.Ibrahim Khider

3. DefinitionDefinition
Dr.Ibrahim Khider

4. DefinitionDefinition
• A precisely orchestrated process
involving PLT, clotting factors and
endothelium that accumulate at the site
of vascular injury and interact to create a
blood clot by which the body stopsDr.Ibrahim Khider

5. • It is a biological or physiological
phenomenon which is responsible to keep
the blood in fluid state in the circulation
as well as to arrest bleeding followed by
an injury to blood vessel.
• The Process is always rapid and localized.
DefinitionDefinition
Dr.Ibrahim Khider

6. Key TermsKey Terms
• Hemostasis
• The process of slowing and stopping the
flow of blood to initiate wound healing.
• Coagulation
• The process by which blood forms
gelatinous clots. Dr.Ibrahim Khider

7. HaemostaticHaemostatic systemsystem
componentscomponents
Dr.Ibrahim Khider

8. The Extra-Vascular
The tissues surrounding blood vessels
 involved in Hemostasis when local vessel is injured.
It plays a part in Hemostasis by providing back-
pressure on the injured vessel through swelling
and trapping of escaped blood.
Dr.Ibrahim Khider

9. The Vascular
• The blood vessels through which blood
flow
– it depends on the size, amount, of
smooth muscle within their walls and
integrity of the endothelial cell lining.
Dr.Ibrahim Khider

10. The Intra-Vascular
• The platelets and plasma proteins that
circulate within the blood vessels.
• These components are involved in:
 Coagulation (clot or thrombus formation)
Or
 Fibrinolysis (clot or thrombus dissolution).
Dr.Ibrahim Khider

11. Concepts of Normal HaemostasisConcepts of Normal Haemostasis
 There is a state of continuous
Balance between bleeding
(hemorrhage) and clotting
(thrombosis).
Dr.Ibrahim Khider

12. Concepts of Normal HaemostasisConcepts of Normal Haemostasis
 Imbalance in one direction
can lead to:
 Bleeding :
 Hypocoagulable state (poor
clot formation or excessive
Fibrinolysis)
OR
 Thrombosis:
 Hypercoagulable state
Dr.Ibrahim Khider

13. Blood
vessels
Platelets
Plasma
coagulation
factors
Inhibitors
Fibrinolytic
system
Components of
Hemostasis

14. Dr.Ibrahim Khider
Types of Haemostasis

15. Primary Haemostasis
 Involves
 Blood vessels (vascular vasoconstriction
phase and release of tissue or exogenous
factors)
 Thrombocytes (platelate or endothelial –
thrombocyte phase, platelate aggregation
and release of platelate factors).Dr.Ibrahim Khider

16. Primary Haemostasis
Dr.Ibrahim Khider
 After 3 to 5 minutes ,
blood flow is arrested
with the formation of a
platelet plug
 Platelet plug
temporarily arrests
bleeding.

17. Secondary Hemostasis
• Involves
• Plasma coagulation factors
(plasma phase)
• Platelate factor 3
 provides for definitive
hemostasis
• Takes 5 to 10 minutes by formation
of fibrin
• Reinforces the platelate plug.
• Clot is removed following healing
of wound
Dr.Ibrahim Khider

18. Tertiary haemostasis
–Fibrinolysis
• Essential final step in any hemostasis
mechanism.
• Enabling in 48 to 72 hours, and a return to
normal by destroying fibrin and healing the
injured vessel.
Dr.Ibrahim Khider

19. Dr.Ibrahim Khider

20. Blood vesselsBlood vessels
• Blood flows through vascular system to and from
all parts of the body.
• The vascular system consists of:
1.Capillaries.
2.Arteries and veins.
Dr.Ibrahim Khider

21. CapillariesCapillaries
• It is the smallest and most
numerous blood vessels in
the body.
• Its lumen is just allow a
single erythrocyte or
leucocyte to pass.
Dr.Ibrahim Khider

22. CapillariesCapillaries
• The metabolic exchange between the
blood and tissues take place in thin-walled
capillaries.
• There are junctions along the capillary
wall that allow the passage of leucocytes,
oxygen, nutrients and waste into and out
of blood. Dr.Ibrahim Khider

23. CapillariesCapillaries
• They are lined with a
single continuous
endothelial cell layer.
• Pericyte are cells that lie
beneath the endothelium
of capillaries and
vessels.
• Pericyte may
differentiate to vessel
related cells whenDr.Ibrahim Khider

24. Arteries and Veins
• They are larger than capillaries
• The physical capabilities of arteries and
veins include:
– constriction and dilation which are
controlled by smooth muscle in these
vessels.
• Vasoconstriction and vasodilation provide
the means for control of blood flow rate
and blood pressure.
Dr.Ibrahim Khider

25. Structure of blood
vessels

26. Structure of blood Vessels
Dr.Ibrahim Khider

27. The tunica adventitia
• The outer part of the vessel wall, consists
of:
 Connective tissue fibroblasts
 Collagen fibers.
Dr.Ibrahim Khider

28. .
The tunica media
• Consists of:
Smooth muscle cells
Collagen fibers.
• It is divided from the
adventitia by the
external elastic
lamina.
Dr.Ibrahim Khider

29. • The intima is the innermost layer.
• The surface is covered with a single layer
of Ecs.
• ESC rest on a basement membrane of
subendothelial microfibrils that are
composed of:
 Collagen fibers
Some elastin.
The Tunica Intima
Dr.Ibrahim Khider

30. Dr.Ibrahim Khider

31. Role of endotheliumin
haemostasis
 The Intact endothelial lining of
blood vessel is non
-thrombogenic ( anti-
thrombotic) layer.
 does not initiate or support
platelet adhesion and blood
coagulation.
Dr.Ibrahim Khider

32. • The non-thrombogenic nature of
endothelium depends on:
– anti-platelet, anti-coagulant and
fibrinolytic substances produced by
endothelial cells.
• This substances contribute to normal
blood flow and prevents abnormal
formation of clots in blood vessels.
Dr.Ibrahim Khider
Role of endotheliumin
haemostasis

33. Substances Released from or found on the
surface of EC
 Prostacyclin
 Inhibit PLT adhesion and aggregation,
stimulates vasodilatation.
 Nitric Oxide
 Inhibit PLT activation, promotes
vasodilatation
 Heparin sulphate
 Coats the endothelial cell surface and
enhance activity of ATIII.Dr.Ibrahim Khider

34.  ADPase (CD39)
 Destroys ADP ( limits PLT activation)
 Endothelin
 Vasoconstrictor.
 Thrombomdulin
 Endothelial surface receptor for thrombin binds
and inactivates thrombin (Protein C/ S system)
 TPA
 Fibrinolytic activity
Substances Released fromorfound on the
surface of EC
Dr.Ibrahim Khider

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37. Vasoconstriction
• Play some role in the control of bleeding
from a injured small vessel.
• Small veins and arteries contain smooth
muscle that contractile powerfully.
• Capillaries are assumed to be non-
contractile.
Dr.Ibrahim Khider

38. • Vasoconstriction reduce blood flow
through an injured area and may be
sufficient, at least temporarily, to
close off a break in small vessels.
Vasoconstriction
Dr.Ibrahim Khider

39. • Reduction in blood flow facilitates the
subsequent steps in haemostasis,
such as
– accumulation of platelets and coagulation
factors at sites of vascular injury.
Dr.Ibrahim Khider
Vasoconstriction

40. Endothelial cells produce vasoconstrictors
such as angiotensin II and serotonin.
Activated platelets produce thromboxane A2
(TXA2) which is a potent vasoconstrictor.
Vasoconstriction

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49. Thanks
Dr.Ibrahim Khider