blood vessels.ppt

1、Blood vessels,The systemic blood vessels are organs of the cardiovascular system, and they form a closed circuit of tubes that carry blood from the heart to the body cells and back again. These systemic vessels include arteries, arterioles, capillaries, venules, and veins. The arteries and arteriole

2、s conduct blood away from the ventricles of the heart and lead to the capillaries. The capillaries are sites of exchange of substances between the blood and the body cells, and the venules and veins return blood from the capillaries to the atria.,Arteries are strong, elastic vessels that are adapted

3、 for carrying the blood away from the heart under relatively high pressure. These vessels subdivide into progressively thinner tubes and eventually give rise to fine branches called arterioles.,The wall of an artery consists of three distinct layers. The innermost layer is composed of a layer of sim

4、ple squamous epiethelium, called endothelium, resting on a connective tissue membrane that is rich in elastic and collagenous fibers.,Capillaries are the smallest blood vessels. They connect the smallest arterioles and the smallest venules. Capillaries are extensions of the inner linings of these la

5、rger vessels in that their walls are endothelium-a single layer of squamous epithelial cells.,Venules are the microscopic vessels that continue from the capillaries and merge to form veins. The veins, which carry blood back to the atria, follow pathways that roughly parallel those of the arteries.,T

6、he walls of veins are similar to those of arteries in that they are composed of three distinct layers. However, the middle layer of the venous wall is poorly developed. Consequently, veins have thinner walls that contain less smooth muscle and less elastic tissue than those of comparable arteries.,Inner layers of the artery,Microcirculation provide oxygen and nutrient for our cells and take the waste away. It also participates in mamy diseases , such as inflammation, wound, burn, shock, hypertension, diabetes, and so on.,Stay aw