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carry blood away from the heart


The smallest arterial branches


where diffusion occurs between blood and interstitial fluid


collect blood from capillary beds, are the smallest venous vessels.


Return blood to the heart

3 layers of arteries and veins

Tunica Intima, Tunica Media, and Tunica externa

Tunica Intima

innermost layer of a blood vessel, Includes the endothelial lining and an underlying layer of connective tissue containing a variable number of elastic fiber.

Internal Elastic Membrane

thick layer of elastic fibers in the tunica intima

Tunica Media

middle layer of blood vessels, contains concentric sheets of smooth muscles tissue in a framework of loose connective tissue.

Tunica Externa

outermost layer of blood vessel, is a connective tissue sheath. In arteries, this layer contains collagen fibers with scattered bands of elastic fibers.

How to arteries and veins typically service the same region?

They run side by side.

Difference between arteries and veins

Walls of arteries are thicker than veins, Arteries are thick and strong, they retain their circular shape, cut veins tend to collapse, and endothelial lining of an artery cannot contract.


when arterial smooth muscles contract, thereby constricting the artery


Relaxation of arterial smooth muscles increases the diameter of the lumen in this process.

Vaso constriction and vasodilation affect...

The afterload on the heart, peripheral blood pressure, and capillary blood flow.

Elastic arteries

or conducting arteries, are large vessels with diameters up to 2.5 cm. They transport large columes of blood AWAY from the heart.

Examples of elastic arteries

Pulmonary trunk, aorta, pulmonary arterie, common carotid arterie, subclavian arteries, and common iliac arteries

Muscular Arteries

also known as medium sized arteries, or distribution arteries, distribute blood to the body's skeletal muscles and internal organs.


Very small, have a poorly defined tunica externa, and the tunica media in the larger arterioles consists of one or two layers of smooth muslce cells.


bulge in the weakened wall of an artery


Permeate most tissues, form intricate networks that surround muscle fibers, radiate through connective tissues, and branch beneath the basal laminae of epithelia. They are the only blood vessels whose walls permit exchange between the blood and the surrouding interstial fluids.

A typical capillary consist of what

Endothelial tube inside a delicate basal lamina

Continuous Capillary

the endothelium is a complete lining. They are located in all tissues except epithelia and cartilage and they permit the diffusion of water, small solutes, and lipid-solubel materials into the surrounding interstitial fluid, but prevent the loss of blood cells and plasma proteins.

Fenestrated capillaries

Contain windows, or pores that penetrate the endothelial lining. The pores permit rapid exchange of water and solutes as large as small peptides between plasma and interstitial fluid.

Examples of fenestrated capillaries

Choroid plexus of the brain and blood vessels in a cariety of endocrine organs, such as the hypothalamus and the pituitary, pineal, and thyroid gland


also called sinusoidal capillaries, resemble fenestrated capillaries that are flattened and irregulary shaped.

Capillary bed

or capillary plexus, interconnected network


multiple arteries, enter the region and fuse before giving rise to arterioles.

Arterial anastomosis

joining of blood vessels, the fusion of two collaterial arteries that supply a capillary bed

Arteriovenous anastomoses

direct connections between arterioles and venules


is the formation of new blood vessels under the direction of vascular endothelial growth factor


The cycling of contraction and relaxation of smooth muscles that changed blood flow through capillary beds

Medium sized veins

range from 2-9 mm in diameter. In these veins the tunica media is thin and contains relatively few smooth muscle cells.

Large veins

Include the superior and inferior venae cavae and their tributaries within the abdominopelvic and thoracic cavities.


folds of the tunica intima, that project from the vessel wall and point in the direction of blood flow.

What percent does the heart, arteries, and capillaries in the pulmonary and systemic circuits normally contain?

30-35% of blood volume.

What percent of blood volume does the venous system usually contain?

65-70% about 3.5 liters.

1/3 of circulating venous blood is circulating in what?

Liver, bone marrow and skin

Capacitance vessels

veins which expand easily


reduces the amount of blood within the venous system, thereby increasing the volume withing the arterial system and capillaries.

Venous reserve

the amount of blood that can be shifted from veins in the liver, skin, and lungs to the general circulation. It is normally about 20% of total blood volume.

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