The vital air called Apana, by the help of the heat that is in the urethra, abdomen and intestines, moves, carrying out urine and excreta.
बस्तिमूलं गुदं चैव पावकं समुपाश्रितः। वहन्मूत्रं पुरीषं चाप्यपान: परिवर्तते॥