Ayurveda considers that every living being is made from the combination of Panchamahabhutas, i.e. the 5 basic eternal substances or elements. These are: Solid (Prthvi), Liquid (Jala), Energy as heat and light (Tejas or Agni), Dynamic energy state of matter (Vayu) and the time-space entity (Akasa) and the soul. Similarly, the universe and everything contained within it is made of the Panchamahabhutas and the universal consciousness.

The human body is composed of three fundamental constructs called Doshas (3), Dhatus (7), and Malas (3). The Tridoshas (i.e. 3 doshas- Vata, Pitta, Kapha) are composed of the panchamahabhutas, where one dosha or the other is predominant. For example, the Vata Dosha has Akasa and Vayu predominating; the Pitta Dosha has Tejas predominating; and the Kapha Dosha has Jala and Prthvi predominating. The Saptha Dhatus are the seven basic tissue elements that make up the structure of the human body and include Rasa (Chyle, Lymph, Plasma), Rakta (Haemoglobin fraction in blood), Mamsa (Muscle tissue), Medas (Fat or Adipose tissue), Asthi (Bone-tissue, including cartilage), Majja (Bone Marrow), and Sukra (Semen, Sperm, Ovum). The Malas are the waste products of the body. The principal malas include urine, stool and sweat. The other waste products are fatty secretions of the intestines or skin, ear-wax, mucous of the nose, saliva, beard and body hair, nails of the fingers and toes, tears, etc.

Agni is the primordial digestive fire in the body - tantamount to enzymes - which are responsible for the conversion of foods into Doshas, Dhatus and Malas. Agni therefore has a two-fold role - to help digestion (breaking down-catabolic metabolism) and assimilation (synthesis, regeneration and growth-anabolic metabolism) in the body. There are 13 main groups of Agnis: Jatharagni (in the GI tract) enables the primary digestive process and breaks down the food. Thereafter the broken-down food is broken up into the 5 Mahabhutas by the 5 Bhutagnis (mainly in the liver) so that the essential constituents of the ingested food are ready for absorption and assimilation. Thereafter, the 7 Dhatvagnis assimilate and ensure renewal/growth of the 7 dhatus-tissue elements which constitute the human body.

Srotamsi or Srotas represent the channels in the body through which the Doshas, Dhatus, and Malas circulate. The Srotas, 13 in number, include the big channels such as the GI tract as well as micro channels such as the capillaries.

For proper functioning of the body, the agni has to function in equilibrium (Samagni under the influence of the three doshas in equilibrium), and function without weakening (Mandagni under the influence of Kapha), or not function excessively (Tikshagni under the influence of Pitta) or not function unstably, i.e. agni which oscillates between less and more (Vishamagni under the influence of Vata). Further the srotas has to remain unobstructed and circulation must proceed in an uninterrupted way, failing which the process of metabolism is affected and Ama or toxins are produced. Usually an organ or tissue that is intrinsically weak or which is similar in mahabhautic composition has a greater tendency to accept the ama or toxin, leading to manifestation of disease in this organ or tissue.