| The areola contains softer and darker skin tissue which surrounds the nipple and which also contains smooth muscle fibers. |
| This contraction arises from excitation of the circular layer of smooth muscle by autonomic nerves. |
| A microvillous tegument was appreciated overlying a thin layer of smooth muscle and a single row of stromal cells. |
| The efflux of potassium ions hyperpolarizes the cell membrane, resulting in vascular smooth muscle relaxation. |
| This drug relaxes arteriolar smooth muscle and has been used in the treatment of severe hypertension. |
| Some veins do not possess smooth muscle fibers and, as a result, do not have a tunica media. |
