The seven Dhatus are the seven tissues of the body. In English they are plasma, blood, muscle, fat, bone, marrow / nerve, and reproductive tissue. In Sanskrit, they are rasa, rakta, mamsa, medas, asthi, majja, and shukra respectively.
These are the structures that make up the body. However, like most concepts in vedic literature, they are much more than their one-dimensional definitions. They are integral to understanding the relationships of the tissues in the body, and they are sites that Doshas enter when they cause disease.
An understanding of the seven Dhatus is important to understanding pathology; what goes wrong in the body. When a dosha enters a Dhatu, a proper understanding of the Dhatu helps the practitioner predict the symptoms that will manifest and provides clues to the best treatment.
Once food is fully digested, the building of tissues commences. Beginning with plasma, the tissues form sequentially, with each layer building upon the layers that come before it. An imbalance within any tissue will, therefore, affect all subsequent tissues. Unhealthy plasma, for example, will affect all layers.
Proper diet and digestion ensure excellent tissue renewal. Plasma is rich in digestive nutrients and actively transfers these nutrients to subsequent tissue layers. In this way, even the deepest and most complex tissues are nourished by the foods we eat. Ojas is the ultimate “essence” of each dhatu. The most effective way to improve the health of the dhatus is to increase ojas. Improper diet and digestion, on the other hand, will lead to ama formation in each tissue layer.
The word rasa literally translates to “juice.” It refers mainly to plasma, but also includes other tissue fluids such as chyle or lymph. Its accessory tissues are breast milk and menstrual blood. Rasa waste product is mucus and its function is Prinana, which means nourishing the body.
Rakta refers mainly to red blood cells. Its accessory tissues are blood vessels and tendons. Rakta waste product is bile and its function is Jivana or invigoration.
Mamsa refers to skeletal muscle. Its accessory tissues are ligaments and skin. Its waste product is everything that accumulates in body orifices such as ear wax, snot, navel lint, etc. Mamsa function is lepama which literally translates to “plastering of the skeleton.”
Meda includes fat in the limbs and the torso. Its accessory tissue is omentum and its waste product is sweat. Meda function is snehana or lubrication of the body. Asthi Dhatu: Bones Ashti includes all bones. Its accessory tissues are teeth and its waste products are body hair, facial hair and nails. Ashti’s function is dharana or supporting the body.
Majja refers to nerves and the contents of bones, which includes red and yellow bone marrow, the brain and the spinal cord. Its accessory tissues are head hair and its waste product are lachrymal secretions. Majja function is Purana or filling of the bones.
Shukra refers to both male and female reproductive fluids. It has no accessory tissues and no waste products. Shukra has two functions, garbhotpatti or reproduction, and the production of ojas, the fluid which creates the aura and controls immunity.