Diploma Paper on Asthma - Essay Example

In my practice, however, I have seen some patients who are in such a phase that the patient experiences some degrees of airways obstruction daily. Prevalence: Asthma is very common; it is estimated that 4% to 5% of the population is affected with this condition. It occurs in all ages but predominantly seen in early life. About 50% of the cases develop before the age of 10, and another 33% occur before age 40. In childhood, there is a 2:1 male to female ratio, but this sex ratio equalises by age 30 (Neri, M.

and Spanevello, A., 2000). Normal Anatomy: The larynx opens into a tube called trachea. This is approximately 5 to 6 inches long, and it is supported and kept open by a series of C-shaped rings of cartilage stacked one upon the other and open at the dorsal aspect. The area between the adjacent cartilages and between the tips of the cartilage contains connective tissue and smooth muscle. The trachea, thus, furnishes an open passageway for both incoming and outgoing air. Its ciliated lining cells also filters air and removes particulate matters before it enters the bronchi, brushing mucus-entrapped particles to the pharynx to be swallowed.

The trachea branches into two primary bronchi, which have the same structure as the trachea. The bronchi become smaller and smaller as they extend towards the lungs, and eventually, their diameter is reduced to about 1 mm. At this point structurally, they seem to lack cartilages that were evident in the upper parts of the tract ( Frechette, E. and Deslauriers, J., 2006). When they start lacking the cartilaginous rings, these are termed as bronchioles. Bronchioles are composed entirely of smooth muscles supported by connective tissues.

They, likewise, continue to branch and sub-branch until they form the smallest air passages, the terminal bronchioles. The branching and rebranching pattern of the trachea, bronchi, and bronchioles constitute a conducting network within the lung referred to as bronchial tree. The terminal bronchioles enter into the alveoli supplying inhaled air and receiving exhaled air (Begueret, H., Berger, P., Vernejoux, J. M., Dubuisson, L., Marthan, R., and Tunon-de-Lara, J. M., 2007).Control of Airway Caliber: Human lungs receive cholinergic, adrenergic, and peptidergic efferents and several types of efferents.

These innervations by the autonomic nerves regulate many aspects of airway function. It has been suggested that the neural control of the airways may be abnormal in asthmatic patients, and neurogenic mechanisms may contribute to the pathogenesis and pathophysiology of asthma. The parasympathetic nervous system is the dominant neuronal pathway in the control of airway smooth muscle tone. Stimulation of cholinergic nerves causes bronchoconstriction, mucus secretion, and bronchial vasodilatation (Janssen, L.J., Wattie, J.

, Lu-Chao, H., and Tazzeo, T., 2001). Sympathetic nerves may control tracheobronchial blood vessels. Although no sympathetic innervations of human airway smooth muscles have been demonstrated, beta-adrenergic receptors are abundant in the airway smooth muscles, and activation of these receptors causes bronchodilation. Inhibitory non-adrenergic, non-cholinergic nerves (NANC) containing vasoactive intestinal peptides and nitric oxide may be the only neural bronchodilator pathways in the airways.

Thus, the classical view with one excitatory (cholinergic) and other inhibitory (nor-adrenergic) components