What is the fluid in an insect's circulatory system called?

What is the fluid in an insect's circulatory system called?

• A. Hemolymph
• B. Blood
• C. Plasma
• D. Lymph

Answer: (A)

Insects use an open circulatory system, so the circulating fluid that bathes organs is called hemolymph. The heart pumps this fluid into the body cavity (the hemocoel), where it glides around tissues rather than being confined to vessels like vertebrate blood. Hemolymph serves as a transport medium for nutrients, hormones, and wastes, and it also carries immune cells, but most oxygen delivery is handled by the tracheal system rather than by the circulatory fluid. This distinguishes it from blood, plasma, and lymph: blood refers to the circulating fluid in vertebrates with a closed system, plasma is its liquid component, and lymph is interstitial fluid in the vertebrate lymphatic system.

Insects use an open circulatory system, so the circulating fluid that bathes organs is called hemolymph. The heart pumps this fluid into the body cavity (the hemocoel), where it glides around tissues rather than being confined to vessels like vertebrate blood. Hemolymph serves as a transport medium for nutrients, hormones, and wastes, and it also carries immune cells, but most oxygen delivery is handled by the tracheal system rather than by the circulatory fluid. This distinguishes it from blood, plasma, and lymph: blood refers to the circulating fluid in vertebrates with a closed system, plasma is its liquid component, and lymph is interstitial fluid in the vertebrate lymphatic system.