a-short-review-of-histology

Veins:

Veins are the collecting vessels of the cardiovascular system
They collect the blood, at virtually zero pressure, from the capillary beds and transport it back to the heart
Veins are generally thinner walled than the arterial vessels that they are related to
In the main, they have little or no muscle in the tunica media
They tend to have a thick tunica adventitia which is important for supporting the walls of the veins as well as for attaching them to surrounding structures
In arteries, the muscle of the tunica media is mainly responsible for maintaining the structural integrity of the wall
Veins provide channels through which blood may flow
Movement along the veins is largely a combination of external factors acting on the veins, valves in the veins controlling direction of flow, and gravity
There is considerable variation in the structure of the walls of veins which can be related to their position in the body and/or the effects of gravity
In general, veins superior to the heart are thinner walled than veins which lie inferior to the heart
In the limbs, superficial veins (lying in the superficial fascia) are thicker walled than deep veins (surrounded by muscle and the deep fascia around the muscle groups)

Question:

Answer Submitted

Micrograph of Peripheral Veins:

In this micrograph there is a large vein in the centre of the picture
To the left and right of the vein there is an artery
Part of another vein is also shown
Notice that the veins have a thinner wall than their corresponding arteries and that this is largely due to the thinner tunica media of the veins
Although the wall of the vein is collapsed, you should be able to appreciate that the internal diameter of the vein is greater than that of its corresponding artery