The bone that is located at the center of the rib cage is called STERNUM.
There are 24 ribs in the human body and these are divided into two set of bones. The first seven bones are called true ribs and attached by cartilage directly to the sternum, which is at the center of the rib cage. Three of the remaining ribs which are called false ribs are attached to the sternum indirectly while the remaining two, called floating ribs are not attached to the sternum.
The answer is 2- circulatory and excretory
Diffusion has a major part in this. It has proteins embedded in it that allow molecules to diffuse in and out of the cell up and down its concentration gradient.
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