Prana refers to all the ways in which we take in energy. Inhalation is by far the most important vehicle for absorbing prana, but prana is drawn from other energy sources as well. Like food, water and external stimuli. It is the force by which the breath is drawn inside.
Apana is responsible for exhalation and for the downward and outward movement of energy, that is the elimination of wastes. It governs the abdomen and the pelvic region of the body.
Samana is the function of prana that digests and assimilates incoming energy. It is located between the heart and the navel. Thus, on an evolutionary level, it is responsible for the expansion of the consciousness.
Udana Vayu is seated in the throat and the head area. It is responsible for the erect posture of the body, sensory awareness and ability to respond to the world. Also, harmonises and activates the limbs.
Vyana is the force that distributes prana by causing it to flow. It expands and contracts, bends downward and upward and travels to the side. Thus, it pervades the whole body. Besides, it co-ordinates the other prana vayus.
If we understand the role of each prana vayu. We can grasp how the forces of prana serve the whole person. And how disturbances among the pranas lead to illness and reduced quality of life. Thus, more awareness leads to a healthy body, mind and living.
Finally, prana permeates all living beings and matter. Thus, keep your prana radiant and spread the harmony all around!