Rakta Dhatu

Rakta dhatu is the second of the seven bodily tissues, corresponding to red blood cells in Western physiology. While Western medicine considers both red blood cells and plasma as components of blood, Ayurveda divides them into rasa (plasma) and rakta (red blood cells). Together, rasa and rakta dhatus transport specific hormones (agni) from endocrine glands to target tissues, regulate temperature by distributing heat from skeletal muscles and active organs, and bathe all cells to provide a stable liquid composition according to individual prakruti.

While rasa dhatu provides nutrition (prinana), rakta dhatu provides the life function (jivana) and delivers oxygen to every cell—a function of prana. Rakta dhatu thus provides vital life support for cellular activities. Ranjaka pitta, prana vayu, and vyana vayu are all present in rakta dhatu and together are responsible for circulation.

Rakta dhatu is hot, sour, and slightly pungent to the taste, with a metallic quality from hemoglobin. It gives energy, life, warmth, and color to the complexion. Healthy blood confers longevity. Rakta is associated with spanda dhamani (pulsating arteries) due to the presence of prana. The total amount of rakta dhatu in a healthy body is approximately eight anjali (about 5 liters), flowing along with the nine anjali of rasa dhatu (plasma).

When red blood cells are young and fresh, they are flexible and can pass through small capillaries, carrying oxygen and prana from the lungs to peripheral and deep connective tissues. Red blood cells are biconcave—shaped like a ring, thin at the center and thick at the periphery—making them elastic enough to pass through capillaries and yield oxygen easily at their thin center. This is the jivana (life-giving) function of rakta dhatu.

Every cell in the human body is a center of awareness, and that awareness is maintained by red blood cells. The flow of awareness is called prana (intelligence). According to Ayurveda, oxygen is the food of prana, but oxygen is not prana itself—you can pour oxygen into a dead body but it will not bring back life. Every cell has electromagnetic energy that maintains the permeability of the cell membrane, through which lifeless molecules of food, water, and air are transformed into the living cell. This transformation is accomplished by prana with the help of tejas.

The superfine molecules of rakta nourish the brain to yield comprehension, understanding, and biological strength. These superfine molecules fight infection as an oxidative burst from the immune system and create immunity through ojas.

Rakta dhatu is initially formed in the yolk sac of the liver and spleen of an embryo—this is why ancient Ayurvedic yogis identified the liver and spleen as the root of rakta dhatu. After birth, once the lungs begin breathing, erythrogenesis (red blood cell production) shifts to the bone marrow, which has functions of both rakta and majja dhatus.

The life of a red blood cell is about 120 days. As it ages, it becomes fragile because rakta agni begins disintegrating the old cell. This destruction takes place in the liver. From the iron content of disintegrated red blood cells, a modified ranjaka pitta is prepared. Biliverdin is formed from the oxidation of bilirubin by ranjaka agni and rakta agni in the liver, then excreted into bile. The kapha component—globin—from disintegrated hemoglobin nourishes the liver and maintains immunity. Insufficient globin in the liver increases susceptibility to hepatitis.

Asthayi rakta dhatu is carried to the bone marrow by vyana vayu, and the liver recycles iron from disintegrated red blood cells back to the bone marrow for new production. Thus rakta agni and bhuta agni combine with majja dhatu agni to create new red blood cells. Blood vessels are created by amino acids and enzymes (rakta agni) already present in the blood; when cut, new branches form via anastomosis.