Respiration is the act of breathing.
Inhalation or inspiration refers to the intake of air into lungs.
Exhalation or expiration refers to breathing out or the movement of gases from the lungs to the atmosphere.
Ventilation is also used to refer to the movement of air in and out of the lungs.
Diffusion the movement of oxygen and carbon dioxide between the alveoli and the red blood cells
Perfusion is the distribution of red blood cells to and from the pulmonary capillaries.
Types of breathing:
1 Costal (thoracic) breathing
Costal breathing involves the external intercostal muscles and other accessory muscles such as the sternocleidomastoid muscles. It can be observed by the movement of the chest upward and outward.
2 Diaphragmatic (abdominal) breathing
Involves the contraction and relaxation of the diaphragm, and it is observed by the movement of the abdomen, which occurs as a result of the diaphragms contraction and downward movement.
Mechanics and Regulation of Breathing:
During inhalation, the respiratory centre sends impulses along the phrenic nerve causing the diaphragm contracts (flattens), the n s move upward and outward, and the sternum moves outward, thus enlarging the thorax and permitting the lungs to expand.
It is an active process. During a normal, relaxed breath, a person inhales 500 ml of air. This amount is referred to as the tidal volume.
During exhalation, the diaphragm relaxes, the ribs move downward and inward, and the sternum moves inward, thus decreasing the size of the thorax as the lungs are compressed. Normally breathing is carried out automatically and effortlessly. It is an passive process.
A normal adult inspiration lasts I to 1.5 seconds, and expiration lasts 2 to 3 seconds.
Respiration is controlled b (a) respiratory centers in the medulla oblongata and the pons of the brain and (b) çhemoreceptors located centrally in the medulla and peripherally in the carotid and aortic bodies.
These centers and receptors respond to changes in the concentrations of oxygen (02 ) , carbon dioxide (C02 ) , and hydrogen (H+ ) in the arterial blood.