What is the primary function of the alveoli in the respiratory system?

A. Transporting nutrients: Nutrient transport in the blood is primarily the role of plasma, which carries glucose, amino acids, and other substances. Platelets do not play a role in delivering nutrients to tissues or cells.

B. Oxygen transport: Oxygen transport is the function of red blood cells, which contain hemoglobin to bind and deliver oxygen. Platelets are not involved in carrying oxygen to body tissues.

C. Immune defense: Immune defense is mainly performed by white blood cells, which identify and destroy pathogens. Platelets contribute minimally to immunity and are not the primary defenders against infection.

D. Clot formation: Platelets are essential for hemostasis; they aggregate at the site of blood vessel injury, form a temporary plug, and release factors that initiate the clotting cascade. This function prevents excessive bleeding and is their primary role in the blood.

A. Vitiligo: Vitiligo is characterized by depigmented patches of skin due to the loss of melanocytes. It is not associated with inflammation and does not indicate an active inflammatory response.

B. Pallor: Pallor refers to a pale skin color, often caused by anemia, shock, or decreased blood flow. While it reflects systemic changes, it is not a direct sign of localized inflammation.

C. Erythema: Erythema is redness of the skin caused by increased blood flow to affected areas. It is a hallmark sign of inflammation and indicates vasodilation and immune activity in response to injury or infection.

D. Xerosis: Xerosis refers to abnormally dry skin, which can cause itching and flaking. It does not indicate an inflammatory process but rather a barrier or moisture-related issue.