These are the main constituents of sharir, namely, dosha, dhatu and mala. It is the root cause of Utpati (origin), Sthiti (stability i.e. development & growth) and Laya (destruction) of the body. When they are in Sama Sthiti (equilibrium) they maintain the body in healthy condition but as there is an imbalance or inappropriate proportion (Visam Sthiti) of these it leads to disease and death. Dosha
Dosha controls the physiological activities in the living body (sharir) and is also responsible for pathology. As it has the tendency of disrupting the physiology in Visam Sthithi (improper proportion) it is called dosha, which leads to disease and death.

According to Ayurveda Vata, Pitta & Kapha are the representative of Air, Sun and Moon respectively in the body. Their activity is similar to that of Air, Sun and Moon in nature. The physiological activities going on in the body could be classified into three:

Movement
It is controlled by the Vata Dosha. Anil (air) and its representative Vata do the function of Vikshapa (to motivate) in the universe and sharir i.e. body respectively.

Transformation
It is caused by Pitta Dosha. Pitta do the function of Adan (to absorb and transform) in the universe and sharir respectively.

Lubrication
It is provided by Kapha Dosha. Kapha Dosha also binds two things together. Soma (Moon) and its representative Kapha do the function of Visaya (to water) or greasing in the universe and Sharir (body) respectively. Surya (sun) and its representative.

Dhatu
There are in all seven dhatus in the living body, namely, Rasa, Rakta, Mansa, Meda, Asthi, Majja and Shukra. Dhatus are the main physical constituents of the body and are responsible for the maintenance of physical state of the body. Rightly Dosha and Mala in its Sama Sthiti are also considered as Dhatu because they are also responsible to maintain the physical.

Mala
These are the waste porducts which are to be excreted out of the body. Mala refers to the excretory by-products of the various physiological activities going on in the body. As they are not useful they should be excreted from the body at appropriate time. If they are not expelled from the body then they may cause Malinikrana (toxification) of the body constituents. Purisha (stool), Mutra (urine) and Sweda (sweat) are considered as main excretory product of the body.

Dhatus and Malas tend to be motivated to indulge in pathological activities by morbid Doshas so they are also called as Dushia (one who is motivated to get indulged in developing pathology).