Lung Anatomy (including the aging lung)

The respiratory system undergoes a continual process of change with age. A number of similarities have been noted in the mouse, rat, dog, and human with distension of alveolar ducts immediately beyond terminal and respiratory bronchioles. This enlargement is typically observed in the form of ductasia with alveoli becoming stretched and shallow in affected regions. Although destruction of alveolar walls may occur with age in the normal lung, these changes reflect in large measure an increase in the size and frequency of alveolar pores connecting adjacent alveoli. An increase in the number of alveolar macrophages in the lungs is a common finding with aging. Increased collagen and basement membrane deposition with focal increases in the interstitium also appear in the normal aging process, while the metabolic function of the lungs decreases with age. Environmental factors are likely to influence changes during the aging process that may be associated with asthma, emphysema, and chronic obstructive pulmonary disease.