ओज: तु तेजो धातुनां शुक्रान्तां परं स्मृतम् |
हृदयस्थमपि व्यापि देहस्थितिनिबंन्धनम् ||
Oja is the essence of all the Dhatus. It is basically situated in heart but has influence on whole body. It is one of the most important element for sustaining life.
Aacharya Sharangdhar has mentioned Oja as an Upadhatu of Shukradhatu.