2. fibroblasts
Production of platelets is
regulated by thrombopoietin
secreted by
Normally
endothelial cells
certain leucocytes
of platelets are present % 75 â 60
in the circulating blood
25 â 40 % of platelets are present
in the spleen
4. Structure of platelets
I- Plasma membrane
plasma membrane contains***
glycoprotein receptors
For
âą collagen
âą fibrinogen
âą vessel von-Willebrand factor
Phospholipids
I
Ù nclude
âą platelet factor 3
5. *** The plasma membrane invaginates
into the interior of the platelets to
form the open canalicular system
serves as a pathway
uptake of extra
cellular calcium
release of intracellular
substances
*** There is also a coat of glycoprotein on
its surface which helps its adhesion to
injured endothelium; but not to normal
endothelium
6. II â Platelet cytoplasm
1- Contractile proteins
actin
thrombosthenine
myosin
enable activated platelets to change
their shape
7. 2- A skeleton of microtubules that keeps
the disc shape of platelets
Residuals of- 3
endoplasmic reticulum
Synthesis
of enzymes
Golgi apparatus
Calcium
store
4- Mitochondria and enzyme system for synthesis
of ATP and ADP
8. .Lyzosomes containing hydrolytic enzymes- 5
Glycogen granules for production of energy- 6
.anaerobically
7- Enzyme system that synthesize prostaglandins
from phospholipids of the Platelet membrane.
9. types of granules 2- 8
A) Dense granules
contain non-protein
substances
ATP, ADP, Ca++)
)and serotonin
b) Alpha granules
contain the secreted
proteins
âą clotting factors
âą fibrin stabilizing
factor XIII
âą platelet derived
growth factor
10. HEMOSTASIS
By Prof Sameh Shamaa
Prof Of medical Oncology and
Internal medicine
Mansoura Faculty Of Medicine
11. HEMOSTASIS
Def:- stoppage of bleeding from the blood
vessels
Mechanisms
(I) v.c of blood vessels
(II) platelet plug formation
(III) Blood coagulation (fibrinogen fibrin)
(IV) Clot retraction
(V) fibrinolysis to dissolve the clot
12. PRIMARY HEMOSTASIS
includes the processes that result in the
.formation of the platelet plug
-:Necessary factors
The blood vessels : the vessel walls esp. the .subendothelial layer
The platelets: plasma glycoproteins 2fibrinogen
Willebrand factor ,which also
presents inside the platelets
-
13. :Mechanisms
.v.c of the bl. vessel-1
Platelets adhesion to subendothelial layer, ( Willebrand- 2
(factor is necessary for this stage
:adhesion of platelets-ï 3- platelets secretion
their activation and secretion of ADP,adrenaline,
noradrenaline â>
aggregation & activation of other
.platelets
.Aggregation of platelets- 4
.Formation of capillary plug- 5
14. Coagulation of Blood
Def :- represent the conversion of fibrinogen
(soluble protein( to fibrin (insoluble(
meshwork which occludes the point or
vessel rupture.
15. First Step :Activation of factor X
BY One of 2 systems:
I-urgent system
(Extrinsic system.(
II-delayed system
(Intrinsic system.(
16. systems of coagulation
I-urgent system.
Extrinsic system.
12-20'' (seconds(
In vivo only.
Due to tissue damage.
II-delayed system
Intrinsic system.
4-8' (minutes(
In vivo & in vitro
due to contact with foreign surface
â
â
Tissue factor
activation of contact system
â
â
X < ------------------------------------IX a < ---------------- IX
â
Xa
â
2- prothrombin
thrombin
3-fibrinogen
Fibrin
18. INTRINSIC SYSTEM
Necessary factors: XII (Hageman factor(
- Contact system XI
Kallikrene
kininogene
- F. IX
- F. VIII
- F. X
- Ca. ++
- phospholipids of the plateletâs membrane
20. Rest of intrinsic pathway
IX
Platelets
Ca ++
IXa
X
VIIIa
VIII
Xa
II
IIa
21. Second Step: of Coagulation
Thrombin Formation: (IIa)
Factors needed:
- prothrombin (II)
- Xa
- V (acceleririe)
- phospholipids
- Ca + +
Platelets
++Ca
II
IIa
V,Xa
22. 3 Step :Fibrin Formation
rd
Fibrin Formation:------------------------
IIa
XIII
Ia
(Fibrinogen) -------------------(Soluble fibrin)
Insoluble protein
XIIIa