Where does the consciousness (cittas) originate inside the body?
Space is a derived quality of matter, so consciousness cannot be said to take up or exist in space. To say that the mind arises here or there is not really proper in an ultimate sense. Consciousness can arise based on physical entities, and hadaya vatthu is the base for both the mind element and mind consciousness element. This doesn't mean that consciousness arises in the hadaya vatthu.


  According to the Pali commentators, the heart serves as the physical support for all cittas other than the two sets of fivefold sense consciousness, which take their respective sensitivities
  as their bases. In the canonical Abhidhamma the heart-base is not expressly mentioned. The Patthāna, the last book of the Abhidhamma Pitaka, simply speaks of “that matter in dependence on which the mind element and mind-consciousness element occur”. The Commentaries, however, subsequently specify “that matter” to be the heart-base, a cavity situated within the physical heart. (Comprehensive Manual of Abhidhamma 144–5 , Bodhi et al)