Final answer:
The bulky middle coat containing smooth muscle and elastin is the tunica media of arteries. This layer is the thickest and contains elastic fibers and smooth muscle cells, which enable arteries to maintain structure and elasticity necessary for blood circulation.
Step-by-step explanation:
The bulky middle coat, containing smooth muscle and elastin, refers to the tunica media of arteries, which is normally the thickest layer in these blood vessels. The tunica media primarily consists of elastic fibers and smooth muscle cells, whose proportions vary with the distance from the heart. In larger arteries, this layer features the external elastic membrane, which is essential for maintaining structure and elasticity, enabling the artery to withstand and accommodate the pressure of pumping blood.
Elastin is a key protein in connective tissues that allows for significant stretching and recoiling to an original shape, which is crucial for the function of large arteries. It, along with the collagenous fibers, provides structure and flexibility to the vessels.
The bulky middle coat in arteries is called the tunica media. It is the thickest layer in arteries and is composed of smooth muscle cells, elastic fibers, and connective tissue. The tunica media controls the diameter of the blood vessels