Prana originates from the soul, that is, the soul is consciousness and Prana is its lifeforce. The life force arises from the consciousness, hence Prana is said to have originated from the soul. Just as light is produced from the sun, a shadow is produced from the human body, in the same way consciousness arises from the soul. It is not many but one but because of its various functions in the body it is divided into many parts. Pranavayu or the life force of the Prana has been divided into ten parts in the human body, in which five are called the principal Pranas and five are Upaprana or sub Pranas. Prana, Apana, Samana, Udana and Vyana come under the five principal category of Prana. These five Pranas express themselves through five distinct forms called the five Upapranas or sub Pranas, which are known as Naga, Kurma, Krkal, Devadatta and Dhananjaya. The expression of Prana is called Naga, the expression of Apana is called Kurma. The expression of Samana is known as Krkala, the expression of Udana is called Devdatta and the expression of Vyana is called Dhananjaya. This vital consciousness or energy flows through millions of subtle channels in the body. Prana drives the respiratory system in the human body. This involves the inhaling and exhaling of breath as well as providing the mobility to the chest region. Apana is responsible for the excretory system. It helps in the elimination of the waste materials from our body like, excreta, urine, sweat etc. Samana runs the digestive system. It works by digesting the food and then converting the digested nutrients into blood, tissues, cells etc. Udana operates the carotid artery and also helps us in speech. Vyana helps in running the blood circulatory system throughout the body, it carries nutrients to the different cells of the body, protects the body from the diseases, keeps the body temperature constant and maintains the circulation of blood in the entire body. The body performs the activities of belching, hiccups, etc., with the help of the Upaprana or sub Prana named the Naga. The Kurma Upaprana or sub Prana is responsible for the act of opening and closing the eyes or blinking of the eyes. The Krkala produces hunger and thirst etc. in the body. The Devdutta causes yawning and stretching of the body etc. And the Dhananjaya keeps the muscles of the body taut. Apart from this the Chakras located in the astral body have a close relationship with the pranavayu or the energy of the Pranamaya Kosha as well, each pranavayu is associated with a particular chakra. For example Apana is the pranavayu or the life force of the Muladhara Chakra, the life force of the Swadhisthana Chakra is Vyana, the life force of the Manipura Chakra is the Samana, the life force of the Anahata Chakra is Prana and the life force of the Vishuddhi Chakra is udana.
~ Acharyasri