Platelets

Definition

Platelets, also known as thrombocytes, are small cell fragments in the blood that play a key role in clotting and wound repair. They are an essential component of the body's cellular defenses against injury.

5 Must Know Facts For Your Next Test

1. Platelets are produced from megakaryocytes in the bone marrow.
2. They lack a nucleus and have a lifespan of about 7-10 days in the bloodstream.
3. Upon encountering vascular injury, platelets adhere to the site and release granules that promote clotting.
4. Platelet activation involves shape change, aggregation, and secretion of chemicals like serotonin and ADP.
5. They also participate in innate immune responses by interacting with pathogens and immune cells.

Review Questions

• What is the primary function of platelets in the bloodstream?
• How do platelets contribute to innate immune responses?
• What changes occur when platelets become activated?

Related terms

Megakaryocytes: Large bone marrow cells that produce platelets through cytoplasmic fragmentation.

Clotting Factors: Proteins in blood plasma that work with platelets to form blood clots.

Hemostasis: The process that stops bleeding at the site of an injury involving vascular spasm, platelet plug formation, and coagulation.