Trachea Diffusion of oxygen and carbon dioxide takes place across the walls of the smallest tubes, called tracheoles, which penetrate tissues and even indent individual cells. Gas may be conducted through the respiratory system by means of active ventilation or passive diffusion. Unlike vertebrates, insects do not generally carry oxygen in their haemolymph. This is one of the factors that may limit their size. A tracheal tube may contain ridge-like circumferential rings of taenidia in various geometries such as loops or helices. Taenidia provide strength and flexibility to the trachea. In the head, thorax, or abdomen, tracheae may also be connected
The Human Body (TV series) July 2001 and includes a 50-minute feature on "The Making of the Human Body" - A final overview that reveals the techniques and developments that made the series possible. The series was adapted into a film released for IMAX cinemas. The film won the Giant Screen Theatre Association's Best Film For Lifelong Learning award. The book accompanying the series was written by Anthony Smith. According to one review, "Smith transcends anatomical trivia to record our bodies' powerful tale with empathy and clarity." The Human Body (TV series) The Human Body is a seven-part documentary series, first shown on 20 May