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 the senses to identify what has gone wrong. The Ebers Papyrus refers to many god-like and spiritual infestations of the body that could not be explained at the time. Despite the explanations for maladies by spiritual rational, the interventions described to investigate and see the body were distinctly disconnected for the spirit or life force of the body and was principally about what could be seen or touched. Descriptions of the exact placement of the heart within the body, the circulation of blood are in no doubt accurate as Egyptians practiced embalming their dead by removal of organs and placement