Body parts and astrology.

 If the 3rd house is about inhalation or Praan Vayu it cannot be denied that lungs need to be seen from the 3rd and 4th houses both, the planet representatives being Mercury and Moon, If the moon is heart as specified by classics then what is Sun then while accessing heart both 4th and 5th should be considered. The Aquarius sign is named Hridya Roga now think of Leo as the second part of the axis, the ruling planet is obviously Sun the energy center, Moon is Rakta (blood) which is the prime constituent material that runs through the heart to other parts of the body and chest where the heart is located. So consider both the Moon and the Sun.