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Part of the cardiovascular system, the vasa vasorum is a network of small blood vessels that help supply larger vessels with blood. This phrase literally means "vessels of the vessels" in Latin, describing their function of providing blood and oxygen to arteries and veins that supply blood and oxygen to the rest of the body. The largest blood vessels in the body, such as the aorta, depend on this support network to maintain healthy function. Both oxygenated and deoxygenated blood are carried to and from larger vessels by these tiny blood vessels.
The vasa vasorum is needed to supply large arteries and veins because of their size. In order to effectively receive oxygen from the bloodstream, cells must be very close to a blood vessel or capillary so the oxygen can pass into each individual cell. Most blood vessels and veins absorb oxygen from the blood flowing inside them. However, because the large veins and arteries are by necessity so thick, their outer and middle cell layers cannot be adequately nourished without this additional network of blood vessels to support them by providing oxygenated blood and carrying away deoxygenated blood.
There are three major types of vasa vasorum, classified by where they originate and where they lead. The vasa vasorum internae originate from inside the main artery or vein and pass into the vessel's walls. Vasa vasorum externae originate in the main artery's branches, then return to the main artery or vein to nourish the cells farther away from the vessel's interior. Venous vasa vasorae have their origins in the main artery, then drain into the artery's concomitant vein, or "partner" vein. The exact structure and function of these blood vessels varies depending on which of these types it is and where it is located.
The function of vasa vasorum in supporting the aorta has been the subject of much study. In some areas, the human aorta does not have vasa vasorum, and in these areas, the aorta's walls are much thinner, making anyeurism more likely to occur in those locations. By contrast, dogs and some other mammals do have these vessels in these areas of the aorta, allowing the vessel walls to be thicker and less susceptible to anyeurism. This complex network of vessels is more commonly found in arteries than in veins, possibly because arterial walls tend to be thicker and more muscular than the walls of even the largest veins.
@Sinbad: Syphilis is much less common now than before the rise of antibiotics/penicillin. But still there were 46,042 reported new cases of syphilis in 2011 in the USA, compared to 48,298 estimated new diagnoses of HIV infection and 321,849 cases of gonorrhea in 2011. So it's about as common as HIV (Note: syphilis increases risk of HIV transmission two to five times).
However, 90 percent of cases are in the developing world. In Sub-Saharan Africa, syphilis contributes to 20 percent of perinatal deaths.
Also, in 2011, 72 percent of P&S syphilis occurred among men who have sex with men. In 1997, the rates of syphilis were nearly equal in men and women. By 2007, the rate of syphilis in men was six times that of women
@Snickerish: Syphilis is caused by the spirochete Treponema pallidum. The primary route of transmission in humans is sex (i.e., direct contact with a sore (chancre) on external genitals, vagina, anus, rectum, orally, etc.)
There is another route of transmission: from mother to child- and that's called congenital syphilis. There were 360 reports of children with congenital syphilis in 2011 in the USA.
Lastly, syphilis and vasa vasorum: The treponema invades the aortic wall, leading to obliterative vasa vasorum endarteritis (necrosis of aortic elastic fibers and connective tissue). You can call this syphilitic aortitis. In untreated syphilis, this happens in 70-80 percent of infections.
Syphilitic aortitis is one of the primary lesions of an overarching group of cardiovascular syphilis (presents in the fourth or fifth decade of life, between five and 40(!) years after initial infection). The one year mortality rate of this complication reaches 80 percent because of the high rate of rupturing aneurysms. However, such late forms of syphilis are rare because of penicillin. Interesting stuff.
@Sinbad - There are different names for different syphilis types. There is one the type I had heard of, syphilis the sexually transmitted disease (STD). It is still around, in 2006 approximately 36,000 cases were reported.
I don't know if that syphilis has a connection to the vasa vasorum, it very well may, but in my studying I did see that there was a cardiovascular syphilis that involved the vasa vasorum. I also am unsure if all syphilis types have to be STDs or if that is just that one type! Guess I better keep hitting the study books!
I understand what the vasa vasorum is, and why it is so important in why someone may or may not have an aneurysm or be less likely to have an aneurysm, but I have also heard of a link between the vasa vasorum and syphilis.
Is syphilis a common disease? I thought it was a disease that had been more or less wiped out to the point it was in very few places and in low numbers. Maybe I am confusing it with another disease...
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