Comparative anatomy of the tracheobronchial circulation.

This review considers the similarities and difference between several animal species to determine which are most appropriate for studies of the human bronchial circulation in health and disease. The subgross anatomy of the sheep, cow, pig and horse appear to be similar to that of humans. These species have a major bronchial artery with a consistent location. In humans and other species, there is evidence of anastomoses between the bronchial and coronary circulations. The bronchial circulation provides nutrient supply to the neural structures of all species. The bronchial arteries themselves are innervated by sympathetic and parasympathetic nerves in all species studied. Evidence has been reported that neuropeptides are present in both afferent and efferent fibres innervating the bronchial arteries. The vasa vasorum of the pulmonary arterial system is derived from the bronchial arteries. Hence, bronchial artery blood composition may modulate pulmonary vasomotor responses. In pathological situations, the responses of the sheep's bronchial circulation are similar to those of the human.