Medium or muscular arteries distribute blood to all organs, using their thick muscular walls to maintain steady blood pressure. On this slide of atrium and coronary artery examine the coronary artery as an example of a muscular artery. Also, examine the image below of a smaller muscular artery, which nicely demonstrates the following features of muscular arteries:

• The tunica intima contains a prominent internal elastic lamina
• The tunica media contains many layers of smooth muscle, and although present, elastic fibers are relatively few compared to the tunica media of large or elastic arteries
• The tunica adventitia is relatively thin and may contain a vasa vasorum

Small to medium arteries can be seen on many slides such as these specimens of areolar CT and spermatic cord. They are frequently located alongside a vein and small nerve as seen in this image at the right from a specimen stained with an elastic stain. Be sure you can distinguish arteries from their companion veins, which typically have larger, irregular lumens, thinner walls, a relatively thinner tunica media and a thicker tunica adventitia, and few elastic fibers.
 

Arterioles and capillaries.