How many regions make up the insect hemocoel?

• A. Two
• B. Three
• C. Four
• D. One

Answer: (B)

Insects have an open circulatory system, so hemolymph fills a network of body spaces called the hemocoel. This network is typically described as having three regions: a pericardial sinus that surrounds the dorsal heart, a perivisceral sinus that surrounds the gut and other viscera, and the remaining body sinuses that fill spaces among muscles and in the appendages. Hemolymph flows from the dorsal vessel into these spaces, bathing tissues and performing circulation functions. Recognizing these three regions helps explain how hemolymph can reach different parts of the body even though the system isn’t divided into fully closed cavities. Therefore, the hemocoel is composed of three regions.