Heart and blood vessells
1. Heart and Blood vessells
2. Heart anatomy
3. blood versellsARTERY
4. Human blood vessels: arteries, veins and capillaries
5. Arteries are strong, elastic vessels that are designed to carry blood away from the heart under fairly high pressure. Thesevessels branch into progressively thinner tubes and
eventually give rise to fine branches called arterioles
layer, tunica intima, is composed of simple squamous epithelium, called
endothelium, resting on a connective tissue membrane, which is rich in
elastic and collagen fibers.
The middle layer, tunica media, makes up the bulk of the arterial wall.
It includes smooth muscle fibers, which encircle the vessel, and a thick
layer of elastic connective tissue.
The outer layer, tunica adventitia, is relatively thin and consists chiefly
of connective tissue with irregularly arranged elastic and collagen
fibers. This layer attaches the artery to the surrounding tissues, be it
muscle, adipose, or other tissue types
7. Venules are microscopic vessels that continue from the capillaries and merge to form veins. The veins, which carry the bloodback to the atria,
follow pathways that roughly parallel those of the arteries.
The walls of veins are similar to those of arteries in that they are
composed of three distinct layers. Because the middle layer of
the venous wall is poorly developed, however, veins have thinner
walls and contain less smooth muscle and less elastic tissue than
Many veins, particularly those in the arms and legs, contain
flaplike valves, which project inward from their linings. These
valves are usually composed of two leaflets that close if the
blood begins to back up in a vein. In other words, the valves aid
in returning blood to the heart, since the valves open as long as
the flow is toward the heart, but close if flow is in the opposite