Which structure allows hemolymph to enter the heart from the body cavity?

Which structure allows hemolymph to enter the heart from the body cavity?

• A. Ostia
• B. Aorta
• C. Dorsal vessel
• D. Pericardial sinus

Answer: (A)

In an open circulatory system, the heart acts as a pumping tube that reclaims hemolymph from the body cavity through specialized inflow sites called ostia. These ostia are valved openings along the heart that permit hemolymph to enter from the hemocoel when the heart relaxes, and the valves prevent backflow as the heart contracts. This setup ensures a unidirectional flow back into the heart before the hemolymph is pushed out into the dorsal vessel and distributed to the body. The aorta is the main outbound pathway carrying hemolymph away from the heart, not the entry point. The dorsal vessel is the overall pumping channel that includes the heart, but the actual entry sites are the ostia. The pericardial sinus is the space around the heart where hemolymph is present, not an entry route into the heart.

In an open circulatory system, the heart acts as a pumping tube that reclaims hemolymph from the body cavity through specialized inflow sites called ostia. These ostia are valved openings along the heart that permit hemolymph to enter from the hemocoel when the heart relaxes, and the valves prevent backflow as the heart contracts. This setup ensures a unidirectional flow back into the heart before the hemolymph is pushed out into the dorsal vessel and distributed to the body. The aorta is the main outbound pathway carrying hemolymph away from the heart, not the entry point. The dorsal vessel is the overall pumping channel that includes the heart, but the actual entry sites are the ostia. The pericardial sinus is the space around the heart where hemolymph is present, not an entry route into the heart.