Final answer:
Platelets are small cell fragments crucial for blood clotting by forming a plug at the site of vessel injury and releasing clotting factors. They are critical for hemostasis and are removed from the blood by the liver and spleen after about 10 days.
Step-by-step explanation:
Platelets are essential components of the blood responsible for clotting processes. They are not whole cells but rather small cell fragments that originate from larger cells called megakaryocytes within the bone marrow. When a blood vessel is injured, platelets adhere to the site and form a platelet plug, aiding in the prevention of blood loss. These fragments range in size from 2-4 µm in diameter and have a lifespan of about 10 days in the circulatory system before they are removed by the liver and spleen.
Platelets release important substances known as clotting factors, which trigger a series of reactions that solidify these plugs into durable clots, composed of platelets and plasma proteins, especially fibrinogen that convert into fibrin. These clots then effectively block the breach in the blood vessel, stopping further blood loss and creating a barrier against infection. Hence, platelets are responsible for initiating and sustaining the critical process of hemostasis, the halt of blood flow after vascular injury.