The rib cage in humans is called the thoracic cage. This bony structure in the core part of skeleton encloses the thoracic cavity supporting the pectoral girdle.
Normally, the rib cage has 24 ribs, costal cartilages, the sternum and the 12 thoracic vertebrae. They (rib cage, skin, fascia and muscles) make up the thoracic wall attaching the thorax, neck, back and upper abdomen muscles.
In humans, the rib cage has a critical function in the respiratory system. It surrounds and protects and thoracic cavity in which lungs are located. When we inhale, the muscular diaphragm in the thoracic cavity floor contracts and flattens as the intercostal muscles also contracts lifting the rib cage up and out.
There are 24 ribs with 12 on each side noted by a Flemish anatomist Vesalius in 1543 in his work titled De humani corporis fabrica.
Each rib has a head, neck and shaft. The head has 2 surfaces: one side in contact with the corresponding vertebrae and another side in contact with immediate superior vertebrae. The ribs are connected to the thoracic vertebrae in the back.
The costae verae I-VII or first 7 vertebrosternal ribs allow movement when we inhale and exhale due to their elasticity. They are attached by costal cartilage in the head to the sternum.
The costae spuriae or vertebrochondral ribs are the 8th, 9th and 10th ribs connected to the first ribs by the costal cartilage.
The costae fluctantes or the eleventh and twelfth ribs are also called floating ribs. They are not attached to the sternum, only in the vertebrae.
And the spaces between these ribs are called intercostals spaces which contain nerves, arteries and muscles.