Non specific immune responses

It takes 7 days from the introduction of a pathogen for a specific immune response to begin. The specific immune response engages the use of T and B cells. T-cells are activated in response to a viral pathogen and B-cells are made in response to an introduced bacteria. The cells are very good at their job, however, 7 days is plenty of time for a pathogen to make itself at home, multiply and invade, which could defeat the B and T cells if the introduced pathogen's numbers are not controlled. Our body attempts to suppress the numbers of the pathogen by presenting a counter attack on day 3.

At this time, Complement Protein Activation begins. Complement proteins are made everyday in the liver and circulate in the blood. The classical pathway of activation is as follows: C1 and C2 bond, splitting C2 into C2a and C2b. C2a floats away. 2b bonds with 4 causing 4 to split into 4a and 4b. 2b and 4a bond creating 3. 4a floats away. C3 bonds with 4b and splits into 3a and 3b. C3b then splits C5 into activated C5a and C5b. C5b then binds to C6, C7, C8 and C9 forming a Membrane Attack Complex (MAC) that has lytic capabilities, in which the complex figuratively punches holes in the membrane of the bacteria, resulting in cytolysis. Basically, these holes allow fluid to enter the cell and it explodes. Before the MAC complex is created there is another weapon that is released in the splitting process. C3a and C5a are the most potent vasodilators that have been found. Vasodilation is a major player in the process of inflammation and phagocytosis, which both help to fight invaders.

During class the issue of immunizations and specifically the flu vaccine was discussed briefly. At first I was thinking that if we decreased the use of the flu vaccine (limiting the vaccine to the elderly and children), that maybe the virus wouldn't be forced to change and modify itself. Dana explained that virus's continually evolve anyway and that limiting the vaccine probably wouldn't help. There is the other issue though of the flu vaccine being helpful anyway, since it is a 3 year process to develop it. What are the chances that it will even be the right strand? I am not against vaccines, I just believe in extreme caution in the administration of them. The conversation about vaccines, led me to the situation with antibiotics and how doctors are warning patients and their families to not abuse the medication due to bacteria learning how to modify itself so that it cannot be treated with the normal prescribed antibiotics. Call me crazy, but I have been worried about this for years. If our antibiotics are rendered useless, we are not left with much to defend ourselves against many, many infections.

Arteries and Veins

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?