The processes of respiration and breathing serve to provide oxygen to the body cells. Carbon dioxide produced during respiration and any other unwanted gases are removed from the body.
Respiration is the exchange of gases. In the human body, two kinds of respiration take place.
External respiration, gases are exchanged between the blood and the surrounding air.
Internal respiration, gases are exchanged between the blood and the individual cells of the body.
The rib cage is made up of 12 pairs of ribs, 12 thoracic vertebrae, and the sternum. All 12 pairs of ribs are attached posteriorly to the thoracic vertebrae.
The upper 10 pairs of ribs are attached directly or indirectly to the sternum.
The sternum is located in the midline anteriorly, immediately beneath the skin. There are 12 thoracic vertebrae, joined by intervertebral discs. Their curvature, the thoracic curvature, is concave anteriorly.
The intercostal muscles extend from the vertebrae behind to the sternum in front.
Some various skeletal muscles extend from above and draw the rib cage upward. Others extend from below and draw the cage downward.
The thoracic cavity is the space of the trunk above the diaphragm.
The abdominopelvic cavity is the rest of the trunk cavity below the diaphragm. The abdominopelvic cavity is a closed system.
Breathing is basically the process of moving air into and out of the lungs. The two types of human breathing are costal and diaphragmatic.
They may be used individually and independently, or they may be used in combination.
From the instant of the "first breath," the lungs have a certain total volume called the total lung capacity. During quiet breathing, it amounts to about two-fifths of the total air volume exchanged.
Total lung capacity = Vital capacity + Residual volume
After one exhales as much air as possible, the portion remaining in the lungs is called the residual volume.
The vital capacity of the lung is the total amount of air that can be exchanged during total filling and emptying of the lung.
The thoracic diaphragm is attached to the inferior margin of the rib cage and to the bodies of the lumbar vertebrae behind.
Diaphragmatic inhalation involves the thoracic diaphragm contracting and lowering. Thus, the vertical diameter of the thoracic cavity is increased.
Diaphragmatic exhalation occurs when the thoracic diaphragm relaxes. This decreases the vertical diameter and the volume of the thoracic cavity.