Psycho-physical system

Psycho-physical system – the subtle channels, 'winds', and essences; in Tibetan, tsa, lung, tiklé; in Sanskrit, nadi, prana, bindu.

The Tibetan Book of Living and Dying says:

The human body is compared by the masters to a city, the channels to its roads, the winds to a horse, and the mind to a rider.

Channels

There are 72,000 subtle channels in the body. The three principal channels are: the central channel, which runs parallel to the spine, and the right and left channels, which run either side of the central channel. The right and left channels coil around the central channel at a number of points to form a series of "knots".

Along the central channel, there are a number of chakras, or energy centers, from which other channels branch off.

Winds (or Inner Air)

Through these channels flow the winds, or inner air. There are five root and five branch winds. Each of the root winds supports an element and is responsible for a function of the human body. The branch winds enable the senses to operate.

The winds that flow in the central channel are called 'wisdom winds'. The winds that flow in all the other channels except the central channel are said to be impure, and to activate negative dualistic thought patterns.

Essences

The essences are contained within the channels. There are red and white essences. The principal seat of the white essences is the crown of the head; the seat of the red essence is at the navel.