Abscesses result from invasion of tissues by parasites of sufficient stamina to maintain destructive activities despite the resistance proffered by the host. Unimpaired lungs of robust persons are extremely resistant to invading bacteria; their defensive capacity is extraordinarily high, and they are able to effect relatively scarless repair of sizable lesions. The peculiarities of structure and function of the lung that provide these attributes likewise disclose the pathogenesis of pulmonary abscess and indicate appropriate therapeutic measures.
STRUCTURE OF THE LUNGS
A unique disproportion in the enormous expanse of the five surfaces of the lung and its limited parenchyma richly supplied with blood are the significant structural characteristics. The external or ventilating surface is formed by the bronchial mucosa and the cells lining the 404,000,000 alveoli. The aerating surface is formed by the endothelium lining the capillaries of the lesser circuit, which is devoid of vasomotor control. The nutritive surface is