MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 4. BLOOD SYSTEM

HEMOSTASIS

1. CHARACTERISTICS OF PLATELETS

Platelets, or Blood Platelets, are anucleate, pale formed elements of the blood measuring 2-3 µm. They circulate in the blood and are partially stored in depots (the Spleen, Lungs, and Liver), from which they enter the bloodstream as needed. Platelet counts increase following meals and physical exertion. The primary function of platelets is their involvement in Blood Coagulation (hemocoagulation) and the cessation of bleeding due to the following properties: firstly, their membranes and cytoplasmic granules contain BIOLOGICALLY ACTIVE SUBSTANCES that trigger blood clotting, such as serotonin, adrenaline, calcium, fibrinogen, retractozyme, and thromboplastin precursors; secondly, platelets have The ability to adhere to damaged vascular walls and aggregate, thereby forming a blood clot.

Platelets also perform an angiotrophic function, which consists in providing nutritional support to the vascular endothelium.

In thrombocytopenia (a decreased platelet count), this function is impaired, causing erythrocytes to pass through the vascular endothelial Cells, which leads to hemorrhages.



Last update: 08/08/2026

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