Pranamaya kosha is composed of the five Pranas. The one primary Prana divides into five types according to its movement and direction. This is an important subject in Ayurvedic medicine as well as Yogic thought. PranaPrana, literally the "forward moving air," moves inward and governs reception of all types from the eating of food, drinking of water, and inhalation of air, to the reception of sensory impressions and mental experiences. It is propulsive in nature, setting things in motion and guiding them. It provides the basic energy that drives us in life.
Apana
Apana, literally the "air that moves away," moves downward and outward and governs all forms of elimination and reproduction (which also has a downward movement). It governs the elimination of the stool and the urine, the expelling of semen, menstrual fluid and the fetus, and the elimination of carbon dioxide through the breath. On a deeper level it rules the elimination of negative sensory, emotional and mental experiences. It is the basis of our immune function on all levels.
Udana
Udana, literally the "upward moving air," moves upward and qualitative or transformative movements of the life-energy. It governs growth of the body, the ability to stand, speech, effort, enthusiasm and will. It is our main positive energy in life through which we can develop our different bodies and evolve in consciousness.
Samana
Samana, literally the "balancing air," moves from the periphery to the center, through a churning and discerning action. It aids in digestion on all levels. It works in the gastrointestinal tract to digest food, in the lungs to digest air or absorb oxygen, and in the mind to homogenize and digest experiences, whether sensory, emotional or mental.
Vyana
Vyana, literally the "outward moving air," moves from the center to the periphery. It governs circulation on all levels. It moves the food, water and oxygen throughout the body, and keeps our emotions and thoughts circulating in the mind, imparting movement and providing strength. In doing so it assists all the other Pranas in their work.
The five Pranas are energies and processes that occur on several levels. However we can localize them in a few key ways. Prana Vayu governs the movement of energy from the head down to the navel, which is the Pranic center in the physical body. Apana Vayu governs the movement of energy from the navel down to the root chakra. Samana Vayu governs the movement of energy from the entire body back to the navel. Vyana Vayu governs the movement of energy out from the navel throughout the entire body. Udana governs the movement of energy from the navel up to the head
As a simple summary we could say that Prana governs the intake of substances. Samana governs their digestion. Vyana governs the circulation of nutrients. Udana governs the release of positive energy. Apana governs the elimination of waste-materials.
This is much like the working of a machine. Prana brings in the fuel, Samana converts this fuel to energy, Vyana circulates the energy to the various work sites. Apana releases the waste materials or by products of the conversion process. Udana governs the positive energy created in the process and determines the work that the machine is able to do.
The key to health and well-being is to keep our Pranas in harmony. When one Prana becomes imbalanced, the others tend to become imbalanced as well because they are all linked together. Generally Prana and Udana work opposite to Apana as the forces of energization versus those of elimination. Similarly Vyana and Samana are opposites as expansion and contraction.