When exercising outside on an extremely warm day, the client can feel his heart pounding very rapidly. thinking in terms of the ability of the aorta to stretch to accommodate more blood circulating during exercise and the warm environment, this is an example of the function of which fibrous protein?

Elastin

Explanation:

The elastin fibers are fibers that are present in the matrix of connective tissues. These are produced by the arterial smooth muscle cells and the fibroblasts. These have bundles of ptoteins called as elastin. These fibers can stretch to 1.5 times in their length. These fibers act like a rubber band and are very flexible. These undergoes frequent streching such as in aorta and in some of the ligaments.

Thus elastin proteins will help the aorta to stretch while exercise so as to accomodate more amount of blood.