All these three Lokas also exist in the human body.
Upanishads speak about the existence of the gods in the body:
AGNI VAG BHUTVA MUKHAM PRAVISHAT,
VAYO PRANOBHUTVA NASIKA PRAVISHAT,
ADITYAH CHAKSHUH BHUTVA AKSHINI PRAVISHAT,
DISHAH SHROTAM BHUTVA KARNO PRAVISHAT,
OSHADHI VANASPATAYO LOMANI BHUTVA TVACHAM PRAVISHAT,
CHANDRAMA MANOBHUTVA HRIDAYAM PRAVISHAT,
MRITYU APANOBHUTVA NABHIM PRAVISHAT,
APORETO BHUTVA SHISHNAM PRAVISHAT.
Meaning:
Agnideva stays in the mouth as voice
Vayudeva enters the nostrils as life,
Surya in the eyes,
Disha in the ears as sound,
Oshadhi (medicinal plants) stays in skin as body hair,
Chandradeva as Mana (Mind) stays in the heart,
Mrityudeva (Death) Stays in navel as Apanavayu
Jal Devta resides in the sense organs as Semen,
In the Heart resides an element of Paramatma (Divine) himself who is the supreme ruler of this body.
The body is thus like a miniature universe. Brain is like a vital gate of the human body. As long as it remains open, all the 33 gods enter the body through it and take respective positions in the body. In the body 33 glands are present.
In Yoga Sadhana, only a few Chakras-viz Mooladhara, Swadhisthana, Manipuraka, Surya, Anahata, Vishuddhi, Agya and Sahastrar-have been described. In fact there are thirty-three Chakras in the posterior side the of body, and each chakra possesses the power of its respective god/deity.
Fourteen worlds are said to be in the human body. the seven upper lokas (including that of earth) are the seven chakras from mooladhara through the
sahasrara.
The science of attaining these higher lokas is said to be yoga and on the other hand, there are also 7 nether worlds. attaining these worlds is the methodologies of tantra , a lower level yogic science.
The yogic science allegories can be found everywhere- for eg. the sound from navel results in a positive energy, creating knowledge and communication. this has been allegorically shown as the lotus emerging from the navel of
Vishnu, creating in it Brahma and Saraswati. their union has resulted in the publication of the true knowledge , the
Vedas.