Dhatu is usually translated as “body tissue,” but this definition does not address some important subtleties of meaning. For most people, the term “body tissue” implies something that has structure within the body like muscle or bone. However, not all the dhatus appear in solid form, nor do they always have structure, as in the case of blood. They exist in many forms: liquid, semisolid and solid.
Ayurveda, therefore, gives a definition of dhatu that is more precise and inclusive in its meaning. The dhatus are those substances and structures which are retained by the body and always rejuvenated or replenished. They are a natural part of the body’s composition and give it its physical strength, structural integrity and function. In contrast to this are those substances within the body called mala, which are naturally expelled from the body. The concept of mala will be discussed shortly.
Substances are considered dhatus only as long as they are kept inside the body. When these “retainable” structures are expelled from the body, they are considered to be mala or waste matter because they no longer support the body’s functioning or form part of its make-up. Injury or illness, can create situations where there is loss of blood or other fluids and tissues. If extensive enough, such unnatural loss of the dhatus could lead to death.
Seven Dhatus and their Functions
Rasa – Nutritional Fluid Plasma
Rakta – Blood – Life Force
Mamsa – Muscles – Cover Bones
Meda – Adipose Tissue – Lubrication
Asthi – Bone – Help to Stand and Walk
Majja – Bone Marrow – Nerve Tissue Nourishment
Shukra – Semen / Ovaries – Reproduction
There are seven dhatus which compose the retainable structures and substances of the body: rasa is the nutrient fluid or plasma that forms the basis of blood or rakta, the second dhatu. The third is mamsa or muscle tissue and the fourth is meda or adipose tissue (fat). Asthi is the term given to bone, the fifth dhatu and majja the term used to signify bone marrow and nerve tissue. The last of the seven dhatus is called shukra, the reproductive tissue of semen in the male and ovum in the female. In this text, we’ll favor the Sanskrit names for the dhatus, since the English terms suggest meanings that are less precise.
The dhatus were listed in the above manner because they develop in the body in a fixed, sequential manner, one from the other. Each succeeding dhatu is a metabolic refinement of the previous dhatu, and gets nourished by it. Rasa (nutrient fluid) is the first dhatu to form, and is the metabolic end-product of the digestive processes that take place within the gastrointestinal tract. The metabolic processes that work on rasa dhatu then produce rakta (blood). Both of these dhatus have liquid forms and circulate all over the body.
The next dhatus to develop have more solid structures. Mamsa (muscle) comes from rakta (blood) and, in turn, gives rise to meda (fat). Asthi (bone) is the product of meda metabolism. It is the most solid of the dhatus and lies deep in the structure of the body. Asthi contains majja, the semi-solid substance of bone marrow and nerve tissue. Shukra is the last dhatu to be created and is the most refined. Ayurveda describes shukra as the semi-solid reproductive tissue which lies within the male and female reproductive systems. According to Ayurveda, shukra also diffuses throughout the body in subtle form.
The developmental sequence of the dhatus is reflected in the manner in which a human fetus matures. The initial stages of fetal growth are characterized by the formation of the first dhatus in the series —nutrient fluid, blood and muscle tissue. The deeper dhatus, such as bone, marrow, and a subtle form of reproductive tissue, arise later. It takes a full nine months for all the dhatus to mature enough to maintain the body through their respective functions. Each works in such intimate coordination with the others that, if a baby is born prematurely, the dhatus will not have had time to evolve into their full functional capacities. As a result, the premature infant’s ability to survive is sometimes questionable.