Structure of Platelets

Platelets are irregularly shaped, small discoid cells, measuring 2-4 μm in diameter. They lack a nucleus and are formed in the bone marrow from the fragmentation of megakaryocytes, which are large precursor cells. Platelets contain numerous secretory granules, which store various substances including clotting factors, enzymes, and growth factors.

Function of Platelets

Platelets are primarily involved in the formation of blood clots, which is essential for preventing excessive bleeding. When a blood vessel is damaged, platelets adhere to the site of injury and become activated, leading to the release of various substances that initiate the clotting process. They also help in the constriction of damaged blood vessels, further reducing blood loss.

Role in Wound Healing

Platelets play a vital role in the initial phase of wound healing. They release growth factors and cytokines that stimulate the proliferation of cells involved in tissue repair, such as fibroblasts and endothelial cells. Additionally, platelets contribute to the formation of a temporary scaffold at the site of injury, facilitating the migration of other cells involved in the healing process.

Regulation of Platelet Function

Several factors regulate the function of platelets. Endothelial cells lining the blood vessels release substances such as nitric oxide and prostacyclin, which inhibit platelet aggregation and help maintain blood flow. Conversely, substances like thromboxane A2 and ADP released from activated platelets themselves can promote further platelet activation and aggregation.

Disorders Related to Platelets

Abnormalities in platelet function or count can lead to various disorders, including thrombocytopenia (low platelet count), which can result in excessive bleeding, and thrombocythemia (high platelet count), which may increase the risk of blood clots forming in the vessels.

Study Guide

Describe the structure of platelets and their origin.
Explain the role of platelets in blood clotting and wound healing.
Discuss the regulatory mechanisms that control platelet function.
Identify and explain the disorders associated with abnormal platelet count or function.

◂Chemistry Worksheets and Study Guides High School. Matter and Energy

The resources above cover the following skills:

PHYSICAL SCIENCE (NGSS)

Matter and Its Interactions

Students who demonstrate understanding can:

Develop a model to illustrate that the release or absorption of energy from a chemical reaction system depends upon the changes in total bond energy.

Energy

Students who demonstrate understanding can:

Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as either motions of particles or energy stored in fields.