The Brahmana said The Word that is made in the body by Prana, then attains to Apana from Prana. Then changed into Udana and coming out of the body, it covers all the quarters, with Vyana.
ब्राह्मण उवाच प्राणेन या सम्भवते शरीरे प्राणादपानं प्रतिपद्यते च। उदानभूता च विसृज्य देहं व्यानेन सर्वं दिवमावृणोति॥