The morphology and morphometry of the adult normal baboon lung (Papio anubis).

The gross, histological and ultrastructural organisation of the baboon lung was found to be similar to that of the human lung. It is suggested that, in general, the lungs of the non-human primates would serve as ideal models for the study of the human lung. The baboon lung comprises the parenchyma, the gas exchange part of the lung which consists of alveoli, blood capillaries and the tissue of the interalveolar septum, and the non-parenchyma made up of the air conducting passages like bronchi, bronchioles, larger blood vessels, connective tissue and pleura. On morphometric analysis, the parenchyma was found to constitute 87% of the lung, the rest being made up of the elements of the non-parenchyma. The alveoli, blood capillaries and the interalveolar tissue respectively constituted 76, 8 and 16% of the parenchyma. The harmonic mean thickness of the blood-gas (tissue) barrier was 0.475 micron and the arithmetic mean 1.12 micron, the ratio being 1:2.3. The weight specific surface area of the blood-gas (tissue) barrier was 37 cm2/g and the surface density of the tissue barrier in the parenchyma 92 mm2/mm3. The total morphometric pulmonary diffusion per unit body weight was 4 ml O2/min/mmHg/kg and the volume of the pulmonary capillary blood per unit surface area of the tissue barrier 0.84 cm3/m2. Morphometrically the baboon lung was thus observed to be better adapted for gas exchange than that of man but less specialised than that of the smaller monkeys such as Macaca mulatta.