This network of transverse and longitudinal tracheae equalizes pressure muscular system of insects pdf the system. The spiracles can be opened and closed in an efficient manner to reduce water loss.
This is done by contracting closer muscles surrounding the spiracle. In order to open, the muscle relaxes. Several aquatic insects have similar or alternative closing methods to prevent water from entering the trachea. Spiracles may also be surrounded by hairs to minimize bulk air movement around the opening, and thus minimize water loss. The spiracles are located laterally along the thorax and abdomen of most insects—usually one pair of spiracles per body segment. Air flow is regulated by small muscles that operate one or two flap-like valves within each spiracle—contracting to close the spiracle, or relaxing to open it. After passing through a spiracle, air enters a longitudinal tracheal trunk, eventually diffusing throughout a complex, branching network of tracheal tubes that subdivides into smaller and smaller diameters and reaches every part of the body.
Oxygen in the tracheal tube first dissolves in the liquid of the tracheole and then diffuses into the cytoplasm of an adjacent cell. At the same time, carbon dioxide, produced as a waste product of cellular respiration, diffuses out of the cell and, eventually, out of the body through the tracheal system. Each tracheal tube develops as an invagination of the ectoderm during embryonic development. The absence of taenidia in certain parts of the tracheal system allows the formation of collapsible air sacs, balloon-like structures that may store a reserve of air.