The Hatha Yoga, Patanjali Yoga, the Kundalini Yoga, etc. all aim to harmonize the body, Prana, and the mind. Prana is the life-force that supports the body and connects it to the subtle mind. It is the life-force, which enlivens the body, makes the body alive, and accomplishes all the body activities. It is for this reason that a person is considered ‘dead’ when the life-force leave his body.
The Yogic scriptures perceive this Prana, which makes up the vital body, as having five different functions within the gross human body aimed at accomplishing five different tasks that are necessary to keep a person alive. The five different tasks that are vital for sustaining of the body are: inhalation, elimination, digestion, deglutition and sound production, and circulation, and the aspect of the life-force that governs each of these five functions are designated as- Prana, Apana, Samana, Udana, and Vyana.
Mahabharata Shanti Parva (Section 184) states:
“Through the breath called Prana a living creature is enabled to move. Through that called Vyana, they put forth strength for action. That called Apana moves downwards. That called Samana resides within the heart. Through that called Udana one eructates and is enabled to speak in consequence of its piercing through (the lungs, the throat, and the mouth). These are the five kinds of wind that cause an embodied creature to live and move.”