One of the major concepts that we covered in class was contrasting arteries and veins. We started with attempting to define the two and learned that we could not include the transportation of oxygenated vs deoxygenated blood into our definitions because both have one big exception. Arteries are vessels that carry oxygenated blood away from the heart, except for the pulmonary arteries which transport deoxygenated blood. Veins are blood vessels that as a majority, carry deoxygenated blood to the heart, with the same except being the pulmonary veins, which transport oxygen from the lungs to the heart.
Both arteries and veins are composed of three layers: the Tunica Intima, Tunica Media and the Tunica Externa, however, each has its own characteristics. For instance, arteries have a thicker Tunica Media, which is comprised of smooth muscle cells and elastic fibers, to help open and close the arteries. The elasticity is needed to withstand the pressure of the blood as it is pumped through. Veins on the other hand, have a much thinner Tunica Media as they do not need to handle the same amount of force. The outermost layer, the Tunica Intima contains a single layer of simple squamous epithelium (Endolithium), a basement membrane, and in the case of arteries a layer of elastic fibers. The layer of simple squamous epithelium, allows for an easy gas exchange. The outermost layer, the Tunica Externa is also found on both arteries and veins and is comprised of dense irregular connective tissue.
Another striking difference is inclusion of valves in veins. Arteries lack this feature. Valves are used in larger, deeper veins in the lower extremities to prevent the back-flow of blood due to gravity. Skeletal muscles work hard to move the blood toward the heart and valves work in conjunction to stop blood from pooling. Valves that malfunction are said to have lost their patency and varicose veins can occur.
I began wondering if the valves could ever be repaired if the person began regularly exercising so that one, the heart could more effectively pump the blood and two, so that the blood was circulated more effectively. If the patient had a strict exercise regimen, would that be enough to prevent pooling, without one or two valves, if that was all that had lost patency?
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Erika - What I find most interesting about the veins/arteries in our body is how many we have and how teeny tiny some of them are.......I have read from 60,000 in a child to 100,000 in an adult. This includes the microscopic capillaries. If we were to lay an average adults blood vessels from end to end, they would circle the earth 4 times. AMAZING!
ReplyDeleteCheck out this website http://www.madsci.org/posts/archives/1999-01/916069852.An.r.html.
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