Part of the peripheral nervous system, the autonomic nervous system regulates involuntary activity in the heart, stomach, and intestines.

Fiber provides bulk to help the large intestine carry away waste. Good sources of fiber are leafy vegetables, beans, potatoes, fruits, and whole grains.

The gaseous state occurs at a higher temperature range than the solid and liquid states of the same substance. In this state, molecules flow very freely around each other and will spread out as far as they're able. Gases maintain neither a constant volume nor a constant shape.

The two largest veins in the body, the venae cavae, pass blood to the right ventricle which pumps the blood to the lungs through the pulmonary artery. Blood picks up oxygen in the lungs and returns it to the left atrium via the pulmonary vein.

The respiratory system manages respiration which is the process by which blood cells absorb oxygen and eliminate carbon dioxide.