(Ref: Ashtanga Hridaya)
That which supports the body and mind is called Dhatu. Dhatus are developed and nourished by food , thereby they help to nourish and support the body. They are of 7 types and are made of different mahabhuta.
1. Rasa (Essence of food / Precursor of all dhatus)
2. Rakta (Blood)
3. Mamsa (Muscle tissue)
4. Meda (Adipose tissue)
5. Asthi (Bone)
6. Majja (Bone Marrow)
7. Sukra (Structural elements of Reproductive tissue)\
Rasa dhatu is responsible for replenishing and nourishing the body. The nourishment of Rasa dhatu depends on the food intake.
Rakta dhatu imparts color, nourishes the mamsa dhatu. It is vital for the existence and sustenance of life.
Mamsa dhatu provides support and strength to the body. It nourishes the medo dhatu and acts as a sheath by protecting the internal organs.
Medho dhatu produces lubrication to the body and also provides nourishment and strength to the bones.
Asthi dhatu forms the framework and support for the body. Like a tree is supported by stems, the human body is supported by the Asthi dhatu. It holds the body together and provides mobility and structure to the body.
Majja dhatu resides within the asthi dhatu. It fills up the asthi dhatu and nourishes the shukra dhatu.
Shukra dhatu is present all over the body and is responsible for conception.
The nourishment and development of sapta dhatus is a continuous and progressive process. The ultimate essence of the 7 dhatus is called Ojas and it is responsible for the strength of the body.