What is the primary function of leukocytes (white blood cells) in the human body?

• A. Defend the body against pathogens and other foreign substances as part of the immune response
• B. Initiate blood clotting by forming platelet plugs at sites of vessel injury
• C. Maintain plasma oncotic pressure primarily by producing albumin
• D. Transport oxygen from the lungs to body tissues via hemoglobin

Answer: (A)

Verified step by step guidance

1. Identify the role of leukocytes (white blood cells) in the human body by understanding their general function within the circulatory and immune systems.
2. Recall that leukocytes are key players in the immune response, meaning they help protect the body from harmful agents such as bacteria, viruses, and other pathogens.
3. Differentiate leukocytes from other blood components: platelets are involved in blood clotting, albumin is a plasma protein maintaining oncotic pressure, and red blood cells transport oxygen via hemoglobin.
4. Recognize that leukocytes do not participate in oxygen transport or blood clotting but are specialized to detect, attack, and remove foreign substances and infected cells.
5. Conclude that the primary function of leukocytes is to defend the body against pathogens and other foreign substances as part of the immune response.