الفهرس 
materials and methodsOnly 14 pages are availabe for public view
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Abstract
SUMMARY and RECOMMENDATION
Cigarette smoke contains irritants, toxic substances and carcinogenic agents which are responsible for a number of
laryngeal and tracheobronchial diseases.
The present study was carried out to demonstrate the histopathological changes in the larynx and tracheobronchial tree as a result of chronic exposure to both side stream and main stream smoke of cigarettes. A sample of twenty rabbits was chosen and divided into five groups, each containing four rabbits. The first four groups were exposed to cigarette smoke for 2weeks, 4weeks, 3months, and 6months, respectively. The last group was the control one which was exposed to room air only.
Twenty four hours after the last exposure, the animals were sacrificed. The larynx, trachea and lungs were dissected and prepared for histopathological study.
Histopathological examination of the specimens taken from the exposed animals showed many changes varying from mild oedema and congestion up to dysplasia and micro-invasive carcinoma. All the changes were found to be dose and duration
related.
The first group showed mild oedema and congestion of the submucosa, mild peribronchial lymphocytic infiltrate, foci of interstitial haemorrhage and dilated alveoli. The second group
showed the same but accentuated changes. In addition, there were foci of hyperplastic epithelium with loss of cilia.
In the third group, the changes were more accentuated. Hyperplastic changes and loss of cilia were more marked. The lining epithelium showed foci of parakeratosis and squamous metaplasia, in addition to mild dysplasia of the basal cell layer. The pulmonary blood vessles were markedly thickened and the
smooth muscles of the terminal bronchioles were also hyperplastic.
The fourth group showed severe and extensive changes. The interstitial haemorrhage, the lymphocytic aggregation and the emphysematous changes were severe. The epithelium was markedly hyperplastic. The blood vessel walls were markedly thickened. The lining epithelium showed marked dysplastic changes in the form of anaplasia, loss of polarity, hyperchromatic nuclei and multiple mitotic figures. In addition, malignant cells were seen invading the subepithelial layer.
The histologic evidence from this study greatly strengthens the evidence that chronic exposure to cigarette smoke is a major factor in the causation of benign as well as malignant changes in
the larynx and tracheobronchial tree. These changes are both dose and duration related.
We recommend to avoid cigarette smoking as well as passive exposure to cigarette smoke.