Question

Describe the histological structure of the artery.

Answer 1

Hint: Artery is part of the circulatory apparatus. In the human body, arteries carry oxygenated blood from the heart to different parts of the body. All arteries carry deoxygenated blood with an exception pulmonary artery which carries deoxygenated blood towards the lungs.

Complete answer: Arteries are very strong elastic vessels that are able to carry oxygenated blood away from the heart under high pressure. They are divided into thinner tubes that give rise to branched arterioles. Any artery’s wall consists of three distinct layers. The innermost; tunica interna is made up of a layer of simple squamous epithelium known as the endothelium. Below the endothelium, the connective tissue membrane is present which consists of many elastic, collagenous fibres. The endothelium helps to prevent blood clotting and may help in regulating blood flow. It releases nitric oxide which acts on the smooth muscle of the vessel and the vessel gets relaxed. Vein walls are similar but not identical with the artery wall. The middle layer is called tunica media and makes up most of an atrial wall, including smooth muscle fibres and the thick and elastic connective tissue layer. The outermost tunica externa is also known as tunica adventitia is thinner, mostly made up of connective tissue with irregular fibres. It is attached to the surrounding tissue. Smooth artery and arteriole muscle are innervated by the sympathetic nervous system. Vasomotor fibres receive impulses to contract and reduce blood vessel diameter is also known as vasoconstriction. When inhibited, the muscle fibre is relaxed and the vessel diameter is increased, this is termed as vasodilation. Changes in the artery and diameter of arteriole greatly affect the blood flow and pressure.

Note: Larger arterioles also have three layers in their walls, which get thinner as arterioles lead to capillaries. Very small arteriole walls have an endothelial lining and some smooth muscle fibres, with a small amount of surrounding connective tissues.