Morphophysiologic bases for the predisposition of the bovine lung to bronchial pneumonia

The susceptibility of the bovine lung to pneumonia may be attributed to the following morphophysiologic features: 1. The large, rugose, nonciliated surface of the pharyngeal tonsil; retrograde drainage from the pharynx during inflammation; gravitational effects on the predominant ventral parts of the pulmonary lobes. 3. Limited compliance due to abundant interstitial connective tissue. 3. Relatively small lungs for the mass of the animal with low tidal volume and functional residual capacity; lower capacity for diffusion of oxygen across the air-blood barrier than in most mammals. 4. Sensitivity of the bovine respiratory tract to marked alterations in ambient environmental temperatures. 5. Normally high pulmonary arterial pressure.