3.  Platelets or thrombocytes are small
colorless, non nucleated cells.
 With numerous cytoplasmic granules
 Shape is spherical or rod shaped and
become oval or disc shaped when
inactivated.
 Size: 1 to 4 micrometers in diameter.
 Normal life span 8-12 days

4.  Structure:
 Cell membrane
 Microtubule
 Cytoplasm

5.  It is 6 nm thick
 (phospholipids, cholesterol and
glycolipids),Carbohydrates(glycocalyx),
Proteins and glycoproteins
 Platelets surface is negatively charged
 Sialic acid gives negative charge
 Receptors on platelets surface –
collagen , ADP,vWF,fibrinogen
 Surface canalicular system

6.  Platelets has prominent cytoskeleton
 Microtubule
 microfilament

7.  Golgi apparatus
 Endoplasmic reticulum
 Mitochondria
 Microtubule
 Micro vesicles
 Microfilaments
 Granules
 Proteins
 Enzymes
 Hormones.
 Chemical substances

8. The major proteins present are contractile
proteins which are responsible for the
contraction of platelets:
 Actin
 Myosin
 Thrombosthenin

9.  Fibrin-stabilizing factor…. Clotting factor
 Platelet derived growth factor (PDGF)
............. helps repair damaged vascular
walls.
 Von willibrand factor

10.  Alpha granules
 Dense granules

12.  The enzymes present are adenosine
triphosphatase and the enzymes
necessary for the synthesis of
prostaglandin

14.  Destroyed in spleen
 Life span 8-12 days

15.  Adhesiveness
 Aggregation
 Agglutination

17.  Role In haemostasis - vasoconstiction
platelet plug formation
 Role in clot formation
 Role in clot retraction
 Role in repair of injured blood vessels
 Role in immunity
 Transport and storage functions

18.  Normal count – 1.5 – 4.5 lac/cubic mm
 Physiological variation age , sex, food,
exercise , altitude
 Variation with disease
 Thrombocytosis
 Thrombocytopenia

19.  After splenctomy
 After severe injury , hemorrhage , major
surgery
 Blood cancers like CML , myelofibrosis

20.  Idiopathic thrombocytopenic purpura
 Bone marrow depression due to drugs ,
radiation
 Hypersplenism
 Infections like dengue , chicken pox ,
typhoid fever
 Secondary to some other cancers