Why is the circulatory not involved in insect respiratory mechanisms?

Insect respiration is independent of its circulatory system; therefore, the blood does not play a direct role in oxygen transport. ... These openings connect to the tubular network, allowing oxygen to pass into the body (Figure 11.14) and regulating the diffusion of CO2 and water vapor.

Insects have a circulatory system but it is an open one, which is why much emphasis is not laid on it compared to other vertebrates e.g in human when it comes to respiration

Explanation: The circulatory system in vertebrates unlike in insect is closed, meaning that blood is transported all over the body through a confined blood vessle, blood contains hemoglobin (red blood cell) which carries oxygen which aids in respiration, while in

Insects they only have hemolymph (like a blood) which doesn't contain hemoglobin this means that the circulatory system in insect doesn't aid in respiration which is why it is not included in the respiratory system of insect. Oxygen is rather delivered through the trachea of an insect.

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