Description
The internal border (inner border) of first rib is its convex, outer edge. It is one of the two borders of the body of the first rib, the other being the external border. Unlike the other eleven ribs, which have superior and inferior borders, the unique orientation of the first rib gives it external and internal borders.
The internal border of first rib consists of part of the scalene tubercle, provides an insertion site for the scalenus anterior muscle and an attachment site for the suprapleural membrane.
Related parts of the anatomy
