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
Theology of the Body nature of human beings in relation to God. The "Theology of the Body" presents an interpretation of the fundamental significance of the body, and in particular of sexual differentiation and complementarity, one which aims to challenge common contemporary philosophical views. Nevertheless, the pope's personalistic phenomenology is "echoing what he learned from St. John of the Cross" and is "in harmony with St. Thomas Aquinas". Francis Bacon was an early empiricist who focused on problems of knowledge. In his Great Instauration, he argued that the current state of knowledge is immature and not advancing. His purpose was for the human mind