72. Long answer questions III

 

Breathing is associated with the inspiration and expiration of airdigestion and absorption of food ingestion and egestion of waste materialsingestion of food and inspiration of air between the atmosphere and the lungs' alveoli. The diaphragm and the intercostal muscles control it. The diaphragm is a  clover leaf like smooth muscledome-shaped smooth muscleconvergent shaped smooth musclecircular shaped smooth muscle that differentiates the thoracic cavity from the abdominal cavity.

 

During inhalation the diaphragm contracts and descendsdiaphragm relaxes and returns to the dome shapediaphragm contracts and relaxesNone of the above. The sternum and the ribs are pushed up and outwards. The volume of the thoracic cavity thus increases, which creates negative pressure inside the lungsNegative and positive pressure created inside the lungs It won't create any pressure inside the lungs.positive pressure in the lungs. Thus the lungs inflate and draw in air from outside the body.

 

During exhalation, the diaphragm relaxes and descends and the sternum and the ribs are pushed up and outwardsthe diaphragm relaxes and returns to the dome shape and the sternum and the ribs return to the original positionthe diaphragm contracts and descends and the sternum and the ribs are pushed up and outwardsthe diaphragm contracts and returns to the dome shape and the sternum and the ribs return to the original position. The volume of the thoracic cavity decreases, which creates a positive pressure in the lungs. Thus the lungs return to the original position, and thus air is expelled from the lungs.