From Gray's anatomy, 1918, via Wikipedia

The ribcage is a set of 24 bones (12 on each side) that provide support to the chest and protect the heart, liver and lungs. It starts with the sternum, a large piece of cartilage that runs from just below the trachea to just below the heart. From the sternum, seven pairs of bones projects from each side and curve around the thorax or chest and attach to the vertebrae of the spine. Two further pair are attached to the sternum at a common point at the bottom. The last two are attached to vertebrae, but not to the rest of the ribs. The top bone of the ribs is often called the collarbone.

Ribs provide the upper chest with a great deal of protection and support. For example, a rib can easily deflect a knife blade as the rib is much harder. A broken rib can be painful, but a damaged organ can be life threatening.

Some people are missing a set of one or two of the bottom two ribs, while other individuals have an extra. However, despite mythical support for the opposite, men and women usually have the same number of ribs.

Human rib cage at Wikipedia

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