Movements of Breathing Mechanism of Inhalation and Exhalation
Pleura Right upper lobe
Right middle lobe
1. Respiration consists of rhythmically repeated inhalations and exhalations. Inhalation takes place as follows: Jthe muscles participating in inhalation contract under the influence of nerve impulse^/ While contracting the diaphragm descends (flattens) increasing the vertical size of thoracic cavity. Contraction of the external intercostal and certain other muscles elevates the ribs increasing both the anteroposte-rior and transverse size of the thoracic cavity^Thus muscular contraction increases the capacity of the thorax. Since the pleural cavity contains no air and the pressure in it is negative both lungs expand