• Minute round or oval discs

• 2 to 4mm in diameter

• Platelet counts in the peripheral blood - 150,000 to 350,000 per cubic mm

• Functional characteristics include

Platelets contain actin and myosin filaments - utilised to contract the platelet plug.

They also contain some residuals of the endoplasmic reticulum and golgi apparatus.

ATP forming enzyme systems (mitochondria)

Prostaglandins forming systems

Fibrin stabilising factor

Platelet growth factors

A coat of glycoproteins on their surface that causes them to adhere to the injured tissues.