What are the function of platelets?

Answer 1

Platelets play a fundamental role in hemostasis, i.e. keeping blood inside the blood vessel. The opposite of hemostasis is hemorrhaging - bleeding. In simple terms, platelets help form blood clots to stop bleeding. They are also a natural source of growth factors - specifically platelet derived growth factor (PDGF) and transforming growth factor Beta (TGFß), both of which are contained within the alpha granules of platelets. In response to platelet to platelet aggregation or platelet to connective tissue contact, as occurs in injury or surgery, the cell membrane of the platelet is "activated" to release these alpha granules. The alpha granules release these growth factors via active extrusion through the cell membrane. These growth factors are involved with initiating wound healing.

PDGF's main functions are to stimulate cell replication (mitogenesis) of healing capable stem cells and what are also called pre-mitotic partially differentiated osteoprogenitor cells which are also part of the connective tissue-bone healing cellular composite. It also stimulates cell replication of endothelial cells. This will cause budding of new capillaries into the wound (angiogenesis), a fundamental part of all wound healing. In addition, PDGF seems to promote the migration of perivascular healing capable cells into a wound and to modulate the effects of other growth factors.

Cells which are activated by TGFß1 or TGFß2 include fibroblasts, endothelial cells, osteoprogenitor cells, chondroprogenitor cells, and mesenchymal stem cells. If a fibroblast is "activated" it will undergo cell division and produce collagen. An endothelial cell will be stimulated to produce new capillaries. An osteoprogenitor cell will further differentiate and produce bone matrix. A chondroprogenitor cells will further differentiate and produce the matrix for cartilage. A mesenchymal stem cell will be stimulated to mitose so as to provide the large population of wound healing cells needed for completion of healing.

Answer 2

The function of platelets is in clotting. Without them the blood would not clot. They are cell fragments and not cells. They live only 5-9 days.

Too many platelets can cause clots that then can travel and cause blockages in vessels. Too few can cause uncontrolled bleeding.