Charaka Samhita, Sutrasthana 28.3
Rasaadi dhatavah sapta — The seven Dhatu beginning with Rasa are: Rasa (plasma), Rakta (blood), Mamsa (muscle), Meda (fat), Asthi (bone), Majja (marrow), Shukra (reproductive tissue). From these seven, and their upadhatu (secondary tissues) and mala (waste products), the entire body is formed and maintained.

The formation chain

Each Dhatu is formed from the previous one through the action of its Dhatvagni (tissue-specific digestive fire). The sequence: food is digested by Jatharagni (digestive fire) into Ahara Rasa (food essence), which becomes Rasa Dhatu (plasma). From Rasa, through the action of Rasa Dhatvagni, a portion becomes Rakta Dhatu (blood). From Rakta through Rakta Dhatvagni, a portion becomes Mamsa (muscle). The chain continues through Meda, Asthi, Majja, to the final and most refined tissue — Shukra. From the finest portion of Shukra, Ojas is produced.

The classical metaphor: the formation process is like a sequence of pots — when the first pot overflows, it fills the second, which fills the third, and so on. Each Dhatu's formation takes approximately five days according to Sharangadhara Samhita's Dosha-Kala documentation, making the complete seven-tissue formation cycle approximately 35 days from food to Shukra.

Three products of each Dhatu's processing
Charaka Samhita documents that each Dhatu's Dhatvagni produces three results from its processing: Prasad (the nutrient portion that forms the next Dhatu), Mala (the waste product specific to that tissue — ear wax from Mamsa, sweat from Meda, body hair from Asthi, tears from Majja), and Upadhatu (secondary tissues — breast milk and menstrual blood from Rasa, tendons from Mamsa, etc.). Understanding these three products allows the practitioner to assess Dhatu quality from the observable outputs.

The seven Dhatu

Dhatu 1 Rasa रस
Plasma/lymph — Ayu (longevity), Tarpana (nourishment)
Dhatu 2 Rakta रक्त
Blood — Jivana (life-sustaining), Varna (complexion)
Dhatu 3 Mamsa मांस
Muscle tissue — Lepana (coating/plastering the bones)
Dhatu 4 Meda मेद
Fat tissue — Snehana (lubrication of body)
Dhatu 5 Asthi अस्थि
Bone tissue — Dharana (support of the body)
Dhatu 6 Majja मज्जा
Bone marrow and nerve — Sneha (oleation), filling of bones
Dhatu 7 Shukra शुक्र
Reproductive tissue — Dharana (seed-carrying), Garbhotpada (reproduction)