Anatomy and Physiology of BV

8/13/2019 Anatomy and Physiology of BV

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Anatomy and Physiologyof

Blood Vessels


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Main blood vessels

connected to the heart

Arteries

Veins

Capillaries


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General Features of Blood Vessels

All blood vessels, except the very smallest, have three distinct

layers or tunics. The tunics surround the central blood-containingspace - the lumen.

Veins

1.The innermost layer, the tunica intima (also called tunica

interna), is simple squamous epithelium surrounded by aconnective tissue basement membrane with elastic fibers.

2.The middle layer, the tunica media, is primarily smooth

muscle and is usually the thickest layer. It not only provides

support for the vessel but also changes vessel diameter to

regulate blood flow and blood pressure.

3.The outermost layer, which attaches the vessel to the

surrounding tissue, is the tunica adventitia.


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Arteries

Carries blood AWAY form the heart

Two main arteries are pulmonary arteries and systemic arteries

Pulmonary arteries carry blood from the heart to the lungs where the

blood picks up oxygen.

Systemic arteries deliver blood to the rest of the body.

Aorta is the main systemic artery and the largest artery of the body. It supply blood to the head region, the heart itself, and the lower

regions of the body.

A muscular middle elastic and very strong

An inner layer of epithelial cells

- smooth so that blood can flow easily with no obstacles in its path


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Veins The walls of veins have the same three layers as the

arteries. Although all the layers are present, there is less

smooth muscle and connective tissue. This makes the walls of veins thinner than those of arteries,

which is related to the fact that blood in the veins has less

pressure than in the arteries. Because the walls of the veins

are thinner and less rigid than arteries, veins can hold moreblood.


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Similar structure to arteries

Thinner middle and inner layers, outerlayer is the thickest

The lumen is wider than artery

Some veins, inner layer folds inwardvalves to prevent backflow


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Carries blood TO the heart Four main veins are pulmonary systemic superficialand deep veins. Pulmonary arteries carry blood from the heart to the lungswhere the blood picks up oxygen. Systemic arteries deliver blood to the rest of the body. Aorta is the main systemic artery and the largest artery ofthe body. It supply blood to the head region the heart itselfand the lower regions of the body.


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Capillaries Important exchanges of the circulatory system occurshere The capillaries are a single cell in diameter to aid fastand easy diffusion of gases sugars and othernutrients to surrounding tissues.


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A capillary wall is very thin and composed of (endotheliumonly) single layer of cells as it does not have to withstandhigh internal pressure.

A capillary wall is often highly permeable, partly becauseits very thin and partly because of holes in and betweencells in some capillaries (particularly those with highdemand of exchange eg endocrine glands)

lumen

endothelium(one cell thick)

cell


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Important exchanges of the circulatory system

occurs here The capillaries are a single cell in diameter to

aid fast and easy diffusion of gases, sugars and

other nutrients to surrounding tissues.


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#1 Arteries

- Carry blood away from the heart

- All arteries carry oxygenated blood except for the pulmonary artery

#2 Veins

- Carry blood back to the blood.

- All veins carry deoxygenated blood except for the pulmonary vein.

#3 Blood Capillaries

- Carry blood from an arteriole(small artery) to a venule(small vein).- In capillaries, the blood is slowed down, giving more time for the

exchange of substances.

- They branch repeatedly and provide a large surface area for the

exchange of substances between the blood and arteries.

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Anatomy and Physiology of BV