Ayurveda has its own way of describing the body, built from a vocabulary that differs from the anatomy and physiology taught in medical schools today. This section explains that vocabulary so that you can read about Ayurveda with understanding. It does not equate these terms with modern organs or diseases, because they were not defined that way.
Agni is the principle of digestion and transformation. The texts speak of a central digestive fire in the stomach and of smaller fires in the tissues, and they teach that its strength shapes health. Ama is the word for what is left when digestion is incomplete: an unprocessed, sticky residue that the tradition holds can block the body’s channels and be the starting point for illness. Ama is a concept within the tradition. There is no laboratory test for it, and online claims about “detoxing” it should be read with that in mind.
The dhatus are the seven tissues that the texts say build the body in sequence, each nourishing the next: plasma (rasa), blood (rakta), muscle (mamsa), fat (meda), bone (asthi), marrow and nerve tissue (majja) and reproductive tissue (shukra). Alongside them the texts discuss the malas, the waste products, namely stool, urine and sweat.
The srotas are the channels through which substances and functions are said to move, such as those carrying food, water, breath and blood. The tradition describes health as free flow in these channels and disease as obstruction, over-flow or leakage. Ayurvedic anatomy was also taught from observation, and the Sushruta Samhita is notable for describing dissection and surgery.
Ojas is the subtle essence said to be produced when the tissues are well nourished. It is linked in the texts with vitality, resilience and immunity in a general sense. Ojas is a traditional idea and is not a measurable substance, and it should not be confused with the immune system as modern science describes it.
The guides here will take each concept in turn, explain its place in the texts, and say how it relates, where it fairly can, to modern terms. They will describe the Ayurvedic picture and not offer a diagnosis. If you are worried about your health, please see a qualified doctor, and in India a registered Ayurvedic practitioner (BAMS). The medical disclaimer applies to all of it.