Animal Respiratory System
Lungs and Pleura
Palpation - The only evidence of disease manifested on palpation is that of pain.
Percussion - Sound on percussion is best noted over thin chest walls. The sound is resonant normally and is clearer about the middle of the chest in large animals. The sound is clear through-out in small animals. In some diseases, the resonance is more extensive and very clear such as Pulmonary Emphysema or Pneumothorax. The sound is dull and flat over area of consolidation in Pneumonia, in tumors or cysts, in Hydrothorax or in Pleurisy with effusion. In the latter two conditions, the dull sound is made outing the lower portion of the chest up to the upper level of the fluid. The outline of the dull areas is irregular in Pneumonia.
Auscultation—the sounds of lungs are intensified by exercise. The normal sounds are:
1. Vesicular murmur
2. Bronchial sounds
The vesicular murmur is a short sound noted specially on inspiration and is due to stretching of the walls of the vesicles. The vesicular murmur is intensified in dyspnoea and in bronchitis in’ the early stage. It is diminished in thickening of thoracic walls and in pulmonary congestion. It is absent over areas of consolidation in pneumonia, tumours or cysts and over pleural exudates ortransudates. In the latter case; the absence of sound is due partly to displacement of the lungs and partly to collapse. In pneumonia, the solid area is surrounded by a zone in which feeble crepitating sound may be heard.
The bronchial sounds are formed by the larynx. They are blowing sounds and most marked at the middle portion of the lungs. The bronchial sounds like the other lung sounds are synchrony-nous with respiration and most marked during inspiration. Various abnormal bronchial sounds are heard and are called `Bales’ and distinguished as dry and moist.
Dry Rales - are due to passage of air over tough bronchial secretion or over swollen bronchial mucous membrane. They are humming, hiss-in, wheezing or whistling and are noted in the early stages of Acute Bronchitis, Chronic Bronchi-ties and, to a slight extent, in Emphysema or in
Compression of the bronchi with nodules or cysts.
Moist Rales - these rile are gurgling or bubbling. They appear in the stage of exudation in bronchitis and are due to the passage of air through or over the fluid present. They are most marked towards the end of inspiration.
The Crepitate Rales - Fine crackling noises due to separating of adhesive walls of the small bronchial tubes. They are noted in Bronchiolitis, in pulmonary edema and in the early stage and the stage of resolution in pneumonia. In the latter case, they are often called Secondary crepitationsounds. In Acute Pleurisy, during the early stages, that is, in the dry stages, friction sounds may behead comparable with the rustling of silk due to rubbing of dry pulmonary pleura on the costal pleura. These sounds are synchronous with the respiration. When the fluid accumulates in the pleural sac, trickling or splashing sounds synchronous with the respiration at the upper level of the fluid may be noted. In examination of the lungs, Borborygmous and the sounds produced by regurgitation of food or gas through the esophagus must be distinguished.