APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -Arterioles are small arteries that deliver blood to capillaries. Arterioles control blood flow through capillary beds by contracting or dilating the the size of the lumen, and therefore the tunica media layer contains concentric rings of smooth muscle to do this.

Detailed explanation-2: -Blood vessels are usually composed of three layers: the tunica intima, tunica media, and tunica adventitia. The tunica intima consists of a layer of endothelial cells lining the lumen of the vessel, as well as a subendothelial layer made up of mostly loose connective tissue.

Detailed explanation-3: -The tunica media, which in an artery is composed of muscle and elastic fibres, is thinner in a vein and contains less muscle and elastic tissue, and proportionately more collagen fibres (collagen, a fibrous protein, is the main supporting element in connective tissue).

Detailed explanation-4: -Veins. A vein is a blood vessel that conducts blood toward the heart. Compared to arteries, veins are thin-walled vessels with large and irregular lumens (see Figure 6).