Human body include the heart, lungs and liver. Many organs reside within cavities within the body. These cavities include the abdomen and pleura. The circulatory system comprises the heart and blood vessels (arteries, veins and capillaries). The heart propels the circulation of the blood, which serves as a "transportation system" to transfer oxygen, fuel, nutrients, waste products, immune cells and signalling molecules (i.e., hormones) from one part of the body to another. The blood consists of fluid that carries cells in the circulation, including some that move from tissue to blood vessels and back, as well as the spleen and bone marrow.
Catholic theology of the body dominating all subordinate material instincts, becomes similar to God. This similarity must be goal of all human undertaking. Gregory of Nazianzus (330-390) contemplated on the origin of the human body. Man was created by God with body and soul, a visible and invisible part, like the angels. He was created to praise God like they did. The body was given to man, so he may suffer and eventually die, and thus not consider himself to be God. The material essence of the body separates us from God, like a cloud, or, as Gregory stated, like the cloud between the Egyptians