VENTILATION OR BREATHING -

15-16 / minute (In Rabbit 36-38). In children 35 / 1 minute.

1.      INSPIRATION

• In take of air is known as inspiration. First of all external I.C.M. is contracted.
• Ribs become straight. Sternum comes out 1.5 cm. It is thoracic breathing (25%).
• Radial muscles of diaphragm are contracted. It becomes flat.
• It is abdominal breathing or true breathing (75%). Both breathing collectively known as Eupnia.
• Thoracic breathing takes place in deep breath only. It gets stimulation from cerebrum.
• Due to all volume of thoracic cavity is increased & pressure is decreased. (1-3 mm Hg than 760 mm Hg).
• To fullfil this pressure air enters into lungs.

2.      EXPIRATION -

• All muscles are relaxed so it is passive process. Volume is decreased.
• Pressure is increased (1-3 mm Hg than 760 mm Hg). Air is given out.