A Comprehensive Guide to Dhatus – Structural Elements of the Body

Ayurveda, the oldest system of Indian medicine describes various concepts to understand the human body, its anatomy, physiology, pathology, treatment, prevention of disease, diet, and lifestyle modifications. The basis for all these is to understand the fundamentals of dosha, dhatus, and mala.

The word ‘Dhatu’ is a combination of two words in Sanskrit “Dha” and “Tun” means that which nourishes or sustains. The word dhatus also means an essence, constituent, component, an element. The reference to dhatu comes in Rasashastra (the science of metals and its compounds) of Ayurveda which means mineral, metal, etc. There are various other references in Ayurveda where the concept of dhatu is told in an elaborative manner.

1. Three dhatus: The three dhatus here refer to the three dosha- vata, pitta, and kapha.
2. Shad dhatus: The six dhatus means the five mahabhuta– Akash, Vayu, Teja, Jala, and Prithvi and the Atma (the soul).
3. Sapta dhatus: The seven dhatus are the seven components of the body, and they are- Rasa, Rakta, Mamsa, Meda, Asthi, Majja, and Shukra.
4. Ashta dhatus: These are the eight factors that are responsible for the formation of Prakriti. The five Mahabhuta, Ahamkara (ego), Mahat (intellect), and Avyakta (the primordial element/factor).

There are various other concepts of dhatu told in Ayurveda classics with different contexts. Now, here we will discuss the concept of dhatus with reference to the components of the body that nourish the body and its structures. The seven dhatus are the tissues of the human body that sustain life. In its abnormal or vitiated state, it is called dushya. 

The seven dhatus are the Rasa, Rakta, Mamsa, Meda, Asthi, Majja and Shukra which nourish the body and sustain life. The food that is ingested undergoes transformation by Jatharagni (the digestive fire in the gastrointestinal tract) and forms aahara rasa which in turn is transformed by dhatwagni (digestive fire of individual dhatu) into saptha dhatus by providing nourishment to each dhatu in sequence.

In this process of metabolism, there are two components, one is called poshya (the component that nourishes the dhatu itself) and the second is the poshaka (the component that nourishes the successive dhatu). Further, the byproducts called upadhatu and the waste products called mala are also formed. Thus, from Rasa to Shukra dhatu, the nourishment takes place in the succeeding order.

The formation and nourishment of saptha dhatus in Ayurveda is explained with the following theories:

1. Kshira Dadhi Nyaya
2. Kedarakulya Nyaya
3. Khale Kapota Nyaya
4. Eka Kala Dhatu Pushti Nyaya

1. Rasa dhatu: This is composed of Jala Mahabhuta (water element). The first dhatu formed from aahara rasa. It can be correlated with plasma and lymph. The byproduct of this is stanya (breastmilk) and rakta (blood). Kapha dosha is the waste product of rasa dhatu. 
2. Rakta dhatu: It is made up of Teja and Ap Mahabhuta (fire and water element). This is the byproduct of rasa dhatu. Blood and its components can be correlated with raktha dhatu in Ayurveda. Kandara (tendons), sira (blood vessels and artava (menstrual blood) are its byproducts. The waste product is the Pitta dosha. It gets its nourishment from rasa dhatu.
3. Mamsa dhatu: Nourished from the previously formed raktha dhatu, mamsa dhatu is made up of Prithvi Mahabhuta. The nourishment is done by its preceding raktha dhatu. Vasa(muscle fat) and the six layers of the skin are its byproducts and the secretions from the nose, ear, etc are the waste metabolites. It can be compared with the muscle tissue in the body.
4. Meda dhatu: It can be correlated with fat tissue and is composed of Ap and Prithvi Mahabhuta. Snayu (tendons) is the byproduct of meda dhatu while sweda (sweat) is the waste product.
5. Asthi dhatu: This is composed of Prithvi and Vayu Mahabhuta. The preceding meda dhatu nourishes the asthi dhatu and can be correlated with the bones. Kesha (both scalp hair and the hair on the whole body) is its waste product. The byproducts are the nakha (nails) and the danta (teeth).  
6. Majja dhatu: Ap Mahabhuta is the predominant component making up this tissue and gets nourished from the essence of asthi dhatu. Majja dhatu can be correlated with the bone marrow. Kesha is its byproduct and the secretions from the eyes, skin are its waste products after the metabolism is completed.
7. Shukra dhatu: The male and female reproductive system and its other components including the semen and ovum respectively can be correlated with Shukra dhatu. This is made up of Ap Mahabhuta (watery element). This is the final stage of tissue formation and nourishment and is believed to be the essence of all the preceding dhatu.

Assessment of dhatus

These above-described dhatu can be examined depending on the optimum level of nourishment that takes place. Thus, this type of assessment is called sara pareeksha. This is a type of examination where an individual can be categorized into different predominant acquired dhatu and those are named, twaksara, raktasara, mamsasara, medasara, asthisara, majjasara, and shukrasara. This type of examination to diagnose a disease and plan the treatment. 

Functions of Dhatus

1. Rasa dhatu: It provides nourishment to the body, and this is called preenana karma.
2. Rakta dhatu: It is the vital force of the body which is termed jeevana karma.
3. Mamsa dhatu: The body is covered in an organized way giving a good appearance and structure. This is due to mamsa dhatu which does lepana karma (covering).
4. Meda dhatu: The luster that is maintained on the skin, the lubrication that takes place in various structures of the body occurs due to meda dhatu. This is its snehana karma.
5. Asthi dhatu: The asthi dhatu forms the supporting structure of the body and the structures of other tissues like muscles, tendons, ligaments, etc.
6. Majja dhatu: It does the poorana karma (filling). It fills the cavities of the body and in the bones as bone marrow.
7. Shukra dhatu: The reproduction to form the progeny is an important function of shukra dhatu. This is garbhotpadana karma of shukra dhatu.

Importance of dhatus 

The dosha gets nourished from the dhatu. The health of an individual depends on the dhatu and any variation in them leads to disease. In the pathogenesis of the disease, the synergistic effect of dosha–dhatu plays a vital role.

The etiological factors cause vitiation of dosha which further vitiates dhatu leading to the manifestation of the diseases. Thus, in the treatment aspect, dhatu needs to be assessed and planned accordingly.

Whenever purification therapies are administered, the initial phase is to bring the vitiated dosha from the shakha (the peripheral zone) and then expel it from the body. The shakha, here, can be referred to as the dhatu where the morbid dosha has accumulated.

As the dhatu gets nourished, the succeeding dhatu is provided with the proper nourishment, and in the same manner if the preceding dhatu is not functioning properly that cannot nourish the next dhatu in a sequel. Like dosha, dhatu also undergoes kshaya (depletion) or vriddhi (aggravation) depending on the etiology. 

Conclusion

Dhatus are the nourishing entities in the body that nourish the dosha as well. The formation and nourishment of individual dhatu depends on the preceding dhatu. Every dhatu has its own poshya component nourishing the self and poshaka component nourishing the succeeding dhatu. The metabolism that occurs at the individual level of dhatu is done by the respective dhatwagni which metabolises into byproduct and the waste product for each dhatu. Saara pariksha is one of the assessments of dhatus that helps in diagnosis and treatment aspects. 

Reference

1. https://www.wjpmr.com/download/article/103112022/1669772799.pdf
2. https://jaims.in/jaims/article/view/846
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4649578/