The lungs and the skin are both vital to the practice of aromatherapy, as these are the two routes by which essential oils enter the body.

Essential oils evaporate on contact with the air, so when breathed in they are carried with the inhaled air through the nose and into the lungs, passing through the pharynx, larynx, trachea and bronchi. The two primary bronchi, which first bring the air into the lungs, divide into smaller passages, which in turn divide and subdivide into tubes of ever-decreasing size, the smallest being called bronchioli. This is sometimes called the 'bronchial tree' and that indeed is a very graphic description. If you imagine an upside-down tree, with the trachea forming the trunk, the primary bronchi the two main branches, and a network of branches, smaller branches and twigs, you will have a fairly clear picture of how air is distributed within the lungs.

The smallest of these air passages, the bronchioli, lead into even smaller ones, called alveolar ducts, and each of these ends in a group of structures resembling miniscule balloons. If seen in magnification, they would look like bunches of grapes. These are called the alveoli, and this is where the vital processes by which oxygen is supplied to the blood and waste matters removed takes place. The process is sometimes called the 'exchange of gasses'.

The walls of the alveoli are made of the thinnest tissue in the body, and through this fine membrane fluids can pass. The surface of the membrane is always moist, so that oxygen and other soluble particles dissolve before passing through it. Around each cluster of alveoli is a network of miniscule blood-vessels (capillaries) which are also moist, and which also have very, very thin walls. Through these permeate the oxygen and other dissolved substances, and the carbon dioxide and other wastes on the return journey.

The importance of this process in understanding aromatherapy, is that particles of essential oils that have been breathed in can pass through these thin-walled structures, and that is how they enter the bloodstream for circulation to other parts of the body.

Disorders of the lungs, including ASTHMA, BRONCHITIS, COUGHS and PNEUMONIA are discussed under their individual headings.