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.
Muscular evolution in humans Muscular evolution in humans Muscular evolution in humans is an overview of the muscular adaptations made by humans from their early ancestors to the modern man. Humans are believed to be predisposed to develop muscle density as early humans depended on muscle structures to hunt and survive. Modern man's need for muscle is not as dire, but muscle development is still just as rapid if not faster due to new muscle building techniques and knowledge of the human body. Humans are widely thought to be one of the fastest muscle growing organisms due to surplus of calories, specialized amino acids,