That portion of its seat extending to as far as the rectum, is called Apana and from that, arteries arise in the five airs Prana. Prana acted on by the heat, strikes against the extremity of Apana region and then recoiling, it reacts on the heat. Above the navel is the region of undigest food and below it, the region of digestion. Prana and all other airs of the system are seated in the navel.
अस्यापि पायुपयन्तस्तथा स्याद् गुदसंज्ञितः। स्रोतांसि तस्माज्जायन्ते सर्वप्राणेषु देहिनाम्॥ अग्निवेगवहः प्राणो गुदान्ते प्रतिहन्यते। स ऊर्ध्वमागम्य पुनः समुत्क्षिपति पावकम्॥ पक्काशयस्त्वधो नाभ्यामूर्ध्वमामाशयः स्थितः। नाभिमध्ये शरीरस्य प्राणाः सर्वे प्रतिष्ठिताः॥