Name: Cardiac Output
Uploaded: 2019-07-19
Duration: 9 min 40 s
Description: Your cardiac output is calculated by multiplying your heartbeats per minute by the amount of blood pumped with each pulse. Isn't it fascinating? Let's learn more!

Question

Describe the histological structure of blood vessels with labelled diagrams.

Accepted Answer

Histological structure of blood vessels:

Artery: The wall of artery is made up of three distinct coats or layers. Outermost layer is tunica adventitia or tunica externa, middle layer is tunica media and innermost layer is tunica intima or tunica interna. The tunica adventitia is a thick layer and consists of loose connective tissue which is longitudinally wrapped up by the white and yellow elastic fibres. This layer strengthens the vessels and prevents the excessive stretching and rupture of the vessels The tunica media is the thickest middle layer of the artery and consists of circular smooth muscle fibres among the network of elastic fibres. This layer regulates the diameter of the vessel as well as the intravascular pressure The tunica intima is a thin layer adjacent to the lumen of the vessel and consists of three sublayers inner endothelium, middle subendothelium and outer elastic membrane. The endothelium layer is made up of a single layer elongated endothelial cells and forms the surface of the lumen. This layer provides the smoothness of the luminal surface and reduces the frictional resistance to the blood flow. The subendothelium is formed by the areolar connective tissue. The outer elastic membrane is wavy and composed of yellow elastic fibres. Though in arterioles the external elastic membrane and súbendothelium layers are not present.

Vein: The wall of vein is also made up of the same three coats or layers like as an artery. However, the tunica intima and tunica media are relatively thinner because of less elastic and muscular fibres in them. Thus, the wall of a vein is thinner and less elastic but very rigid due to the presence of excessive collagen fibres. Sometimes the foldings of the tunica intima of the veins create valves within the lumen which prevent capillaries the back flow of the venous blood. The lumen of the vein is wider than that of artery.

Capillary: The walls of capillaries are very thin and consist of a unicellular layer of elongated and flatten endothelial cells capillaries resting on a basement membrane located on Iliac artery the outer sides of the capillaries. The capillary wall is porous because of the presence of intercellular clefts at the junctions of the endothelial cells. These clefts (slit pores) allow water, water-soluble ions, small solutes, etc. except proteins and other organic compounds, to cross the wall. Thus, nutrients, waste products, respiratory gases, hormones, etc. are easily exchanged in between the blood and tissue fluid through the capillary walls.

Describe the histological structure of blood vessels with labelled diagrams.

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