The decrease of the average platelet volume will lead to bleeding, which is usually manifested as petechiae, purpura and ecchymosis, and skin and mucous membrane bleeding, gastrointestinal bleeding, menorrhagia and intracranial bleeding in women of childbearing age may occur.

It was not until 1882 that the Italian doctor J.B. Bizzozero discovered that they played an important role in hemostasis after vascular injury, and the name of platelets was first proposed. In lower vertebrates, spindle cells play a role in blood coagulation, and fish begin to have specific platelets. Amphibians, reptiles and birds all have platelets in their blood.

Platelets are spindle-shaped or oval cells with nuclei, and their functions are similar to platelets. Invertebrates have no specific platelets, such as mollusks, which have the functions of defense and wound healing. Crustaceans have only one kind of blood cells, which can also coagulate blood.

Platelets are disc-shaped, ranging in diameter from 1 ~ 4 microns to 7 ~ 8 microns, with great individual differences (5 ~ 12 cubic microns). Platelets can move and deform, so they are polymorphic when observed by general methods.

Platelet structure is complex, in short, it has three layers from the outside to the inside, that is, the periphery consisting of outer membrane, unit membrane and subfilm microfilament structure is 1 layer; The second layer is the gel layer, and microfilaments and microtubules parallel to the surroundings can be seen under the electron microscope. The third layer is the micro-organ layer, which has mitochondria, compact bodies and residual nuclei.