In the Bhagavad Gita, Lord Krishna tells Arjuna about the nature of the body, what it is made up of, what is the purpose of the body, whether it is made of something material (jada) or of something intangible (ajada). But before He begins to explain about the body and the atma, He says that whatever He is going to say has already been said by sages and has been stated in the Vedas.
Moola prakrti is not a transformation of anything, but itself undergoes transformations. Take the example of gold. If gold is prakrti, then we do see it transforming into various kinds of jewellery. So, a bangle made of gold is a vikAra of gold. Can this bangle be the prakrti for something else? Yes, it can. So, some things have both the qualities of prakrti and vikrti. The five elements and the eleven indriyas belong to the category of just vikrti. In other words, they do not transform into anything else. So, everything in the Universe fits into one of these three categories — prakrti, prakrti-vikrti and vikrti, elaborated Valayapet Ramachariar in a discourse.
Kshetra, that is the body, is composed of the five elements — earth, water, fire, air and ether — and ahamkara, buddhi and prakrti. The Lord further says that the five karmendriyas, five jnanendriyas and manas are also present in the body. Desire and dislike are also in the body. However, this raises a question. Dislike, liking, pain and pleasure are experienced by the atma. So, how does the Lord say they are in the body? The reason is that without association with a body, the atma does not experience anything. So, the body is what makes the experience of sukha and dukkha possible for the atma. So, the question as to the purpose of the body is answered here. It makes possible experiences of various kinds for the atma.