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
History of beliefs about the human body is important to understanding histories of coercion and control, sex and gender, and other important but culturally varied aspects of human experience. Another prominent voice in the field at the same time was Caroline Walker Bynum, whose 1988 "Holy Feast and Holy Fast" became a landmark study. Both Bynum and Porter noted that during the 1980s Western history of the body research drew on post-structuralist thought, such as Michel Foucault's ideas of biopolitics and biopower, which emphasised that state power is not abstract, but exercised through and over human bodies. But both expressed a concern that research was focusing too