4. FORMATION
BONE MARROW
BLOOD STREAM
Each megakaryocyte produces
between 1,000 to 3,000 platelets
during its lifetime.
Formation
of
platelets
from stem
cells takes
10 days
5. LIFE SPAN & FATE OF PLATELETS
Life span – 8-12 days
Avg – 10 days.
Fate – Destroyed by tissue macrophage system in
spleen.
Splenomegaly – reduces platelet count.
Splenectomy – increases platelet count.
7. It is 6 nm thick and contain
Carbohydrates(glycocalyx),
Proteins (Glycoproteins)
Lipids (phospholipids, cholesterol and glycolipids)
Out of all glycoprotein and phospholipids are
functionally important.
1 .CELL MEMBRANE
STRUCTURE
8. Glycoproteins:
STRUCTURE
Prevents the adherence of platelets to normal endothelium.
Accelerates the adherence of platelets to collagen and
damaged endothelium in ruptured blood vessels.
Forms a receptor for ADP and thrombin.
Phospholipids:
Accelerated clotting reaction.
Form precusors for THROMBAXANE A2 &
PROSTAGLANDINS.
9. 2.MICROTUBULE
• Made up of tublins (proteins)
• It responsible for structural support
for inactivated platelets
STRUCTURE
16. PROPERTIES
ADHESIVENESS :
Injuty to blood vessel - Vascular Constriction
platelets become stickey and adhere to the collagen
matrix in sub-endothelium.
Factors responsible are collagen, thrombin,
ADP,thromboxane A2, Ca ion& Von-Willebrand Factor.
17. AGGREGATION :
Property to stick to each other Factors
responsible are ADP & Thromboxane A2.
PROPERTIES
18. AGGLUTINATION :
Property of clumping together of
platelet
Its due to platelet Agglutinins.
PROPERTIES
19.
20. 1.ROLE IN HAEMOSTASIS
Haemostasis – spontaneous arrest of bleeding
from injured blood vessel.
Vasoconstriction – by 5HT & other vasoconstrictors
Temporary haemostatic plug – by platelets due to
its property of adhesiveness & aggregation.
Definite haemostatic plug – also initiated by
platelets.
22. 2.ROLE IN CLOT FORMATION
Play role in formation of intrinsic prothrombin activator
It is responsible for onset of blood clotting.
23. Contraction of contractile proteins-
Actin,
Myosin &
Thrombosthenin.
Responsible for clot Retraction & wound healing.
3.ROLE IN CLOT RETRACTION
24. Platelet derived growth factor (PDGF) in
cytoplasm of platelet for Repair of
Endothelium.
4.ROLE IN REPAIR OF
INJURED BLOOD VESSELS
25. 5.ROLE IN DEFENCE MECHANISM
Due to the property of agglutination , platelets are
capable of Phagocytosis.
Mainly in Phagocytosis of carbon particles, viruses &
immune complexes.
26. PLATELET FUNCTION TESTS
Platelet count- Peripheral blood smear
Bleeding time- Dukes Method.
PFA (PLATELETS FUNCTION ASSAY).
Platelet Aggregation Test (Flow cytometry).
27. Platelet count- Peripheral blood smear
Platelet to be counted in a region
where RBCs & platelets are well
dispersed
Atleast 10 oil immersion fields to be
counted.
Average no of platelets in a field
multiplied by 10000 is the approximate
platelets count.
<8 platelets /OIF = decreased.
8 to 20 platelets /OIF = adequate.
>20 platelets /OIF = increased.
PLATELET FUNCTION TESTS
28. Bleeding time- Dukes Method
With the Duke method, the patient is
pricked with a special needle or lancet,
preferably on the earlobe or fingertip.
The prick is about 3–4 mm deep. The
patient then wipes the blood every
30 secs with a filter paper.
The test ends when bleeding stops.
The usual time is about 2-6min.
Other method-IVY METHOD.
PLATELET FUNCTION TESTS
29.
30. PHYSIOLOGICAL VARIATIONS
Age – Less in infant, reach adult level by 3
months of age.
Sex –No difference but during mensturation
reduced in females.
Meal – Increases after meal.
Muscular exercise – Increases.
Altitude – Increases.
36. DENTAL COSIDERATION
Before extraction
Proper history taken from patient:
Stroke Patient on Anti-platelet drugs- Clopidogrel,
warfarin, heparin etc
Hyperlipedimic patient on Asprin for prevention MI.
Advice to stop drugs for 3 days afterwards extraction
procedure done in patient.
Hemorragic disease:
Proper precaution for stop bleeding before extraction procedure.
Gelatin foam
Adrenalin pack
Electrocautery
Thrombin sponge
