Which primary function is performed by erythrocytes (red blood cells) in the human body?

• A. Produce antibodies to target and destroy pathogens
• B. Initiate blood clotting by forming a platelet plug at sites of vessel injury
• C. Secrete hormones that regulate blood pressure and fluid balance
• D. Transport oxygen to tissues and carry some carbon dioxide back to the lungs via hemoglobin

Answer: (D)

Verified step by step guidance

1. Identify the main role of erythrocytes (red blood cells) by recalling their structure and function. Erythrocytes contain hemoglobin, a protein specialized in binding gases.
2. Understand that hemoglobin binds oxygen in the lungs and transports it through the bloodstream to body tissues, where oxygen is released for cellular use.
3. Recognize that erythrocytes also assist in carrying a portion of carbon dioxide, a waste product of metabolism, from the tissues back to the lungs for exhalation.
4. Differentiate erythrocytes from other blood components: for example, leukocytes produce antibodies, platelets are involved in clotting, and certain cells secrete hormones.
5. Conclude that the primary function of erythrocytes is the transport of oxygen to tissues and the return transport of some carbon dioxide to the lungs, facilitated by hemoglobin.