simple and nice.
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.
In costal inhalation, the lungs are expanded and inflated with air because of upward movement of the rib cage. There are two types of upward movement.
In one movement, the so-called "bucket handle" effect occurs on both sides of the rib cage, the transverse diameter of the rib cage increases from side to side.
The second type of movement increases the diameter of the thoracic cavity from front to back by raising the lowest points of the ribs, increasing the volume of the thoracic cavity.
The lungs empty during costal exhalation, a process that is essentially the reverse of costal inhalation. The rib cage moves downward as a whole.
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