Final answer:
Platelets, or thrombocytes, are responsible for blood clotting and defending against infection.
Step-by-step explanation:
Platelets, also known as thrombocytes, play a vital role in blood clotting or coagulation. When there is a tear in a blood vessel, platelets stick to the site of injury and to each other, forming a plug to stop bleeding. They also release chemicals that are necessary for clotting to occur. Platelets are involved in the defense against infection.