Monday, June 18, 2007

Compendium Review Ch. 5-7 & AIDS supplement

Table of Contents:
I. Heart and Blood Vessels
A. Circulatory System
1. Types of blood vessels
a. arteries
b. capillaries
c. veins
B. The Heart
1. Passage of blood
a. Blood to external environment
b. Blood to cells of body
c. Diffusion
C. Regulation of blood flow
1. Blood pressure
a. radial artery
b. cartoid artery

II. Blood
A. Functions of Blood
B. Red Blood Cells
1. Production of
2. Process of carrying oxygen
3. Process of transporting carbon dioxide
4. Disorders
a. sickle-cell anemia
C. White Blood Cells
1. Types of white blood cells

III. Immunity
A. Foreign Invaders
1. Bacteria
2. Viruses
B. Nonspecific Defenses
1. Barriers to entry
2. Inflammatory response
C. Specific Defenses
1. T-cells
a. TCR's
b. clonal selection
2. B-cells
a. BCR's
b. clonal selection
D. Antibodies
E. Macrophages

IV. AIDS
A. HIV and AIDS
1. HIV Life Cycle
2. Transmission
3. Infections caused by HIV/AIDS
B. Epidemiology of Spread of AIDS

The human body is an amazing structure. And it is a very complex, functioning tool that allows the human race to live for such an expanded period of time. But what exactly makes up the internal workings of this complex tool? There are several things that make it possible for people's survival, but the main focus for this review will be four major subjects. They will be the heart and blood vessels, blood, immunity, and AIDS.
The heart and blood vessels consist of a paramount system called the circulatory system. The circulatory system performs the functions of pumping the heart in order for blood to flow through the blood vessels. And the, "...actual purpose of circulation is to service the cells" (Mader 86). This means that as the blood is pumped and flows through the blood vessels, the cells receive nutrients within the blood and wastes are taken away from the cells. This action allows for homeostasis to continue as it keeps a balance of necessary and unnecessary particles within the body. As the blood travels through the blood vessels, it moves throughout three different types of blood vessels.
The first type are the arteries. The arteries are made of three layers. The thinnest layer is called the epidothelium, which is located in the innermost part of the artery, the middle layer is much thicker than the inner layer, being mostly made of elastic tissue and smooth muscle, and the exterior layer is made of mainly connective tissue. Arteries have to, "...expand to accept the blood being forced into them from the heart, and then squeeze this blood on to the veins when the heart relaxes" (http://www.accessexcellence.org/). That is why they are made up of tissues with so much elasticity. The arteries also have branches of arterioles that eventually become capillaries. The second type of blood vessels are the capillaries. Capillaries are very small branches made of one layer of epithelial cells. These small branches make up subunits of capillary beds that are located within all aspects of the human body. The function of the capillaries is where the exchange of blood and the cells occur by providing oxygen for cellular respiration, nutrients for cell metabolism, immune cells for foreign microbes, and the removal of wastes. These processes occur with the aid of blood pressure and osmotic pressure within the capillary walls. At the arterial end (coming from the upper part of the heart) of a capillary, water exits due to the higher blood pressure than the osmotic pressure. And at the venule end (coming from the lower part of the heart) of a capillary, water enters due to the higher osmotic pressure than the blood pressure. But, in the midsection of the capillary, both the blood and osmotic pressures even out and this is where the oxygen, nutrients, and immune cells are provided for the cells and where the waste is removed. When the capillaries begin to become thicker they become venules, which leads to the veins. The third type of blood vessels are the veins. The veins are made of the same components of the arteries, but are much thinner, allowing them to expand more. Veins have valves that, "allow blood to flow only toward the heart and prevent the backward flow of blood when closed" (Mader 87). Veins take the blood back to the heart and repeats the circular process of blood flow from arteries to capillaries to veins and back to the heart.
Figure 1: Visual of the types of blood vessels
The heart is, "...a cone-shaped, muscular organ located between the lungs..." (Mader 88). It is a double pump consisting of two halves. The uppermost areas of the heart are the left and right atrium. And the lowermost areas are the left and right ventricles. The heart muscle allows for the atrium's and ventricles to pump at the same time, creating the passage of blood in three different ways. The first way, passing blood to the external environment, happens in the lungs, digestive system and urinary system. The lungs are brought oxygen by the right side of the heart and carbon dioxide is taken away by the left side of the heart. Then, the digestive system is provided with nutrients by the left ventricle. And lastly, metabolic wastes are released through the urinary system with the aid of the blood vessels. The second way, passing blood to the cells of the body, occurs from the pumping of the left side of the heart. Every tissue is provided with oxygen-rich blood and necessary nutrients and is rid of their oxygen-poor blood (carbon dioxide). And the last way, passing blood by diffusion, allows for the heart to create equilibrium by passing blood throughout the arteries and receiving them in the capillaries. The capillaries diffuses the necessary substances and returns the blood back to the heart. As the passage of blood continues by processes of the heart, they are also regulated by blood pressure.
Blood pressure is, "...the pressure of blood against the wall of the blood vessel" (Mader 92). While the blood is being pushed through the arteries by the pumping of the heart, the walls expand and then take there original shape again. And, if more oxygen is needed by the cells, the heart pumps more blood against the walls of the blood vessels to provide the needed oxygen. Blood pressure can be measured by this action, called the pulse. This can be found on the radial artery, which is located on the palm side of the wrist, and the cartoid artery, which is located on either side of the neck. The pulse provides a sense of the rate of the heart and can be determined by systolic values and diastolic values. For example, the normal range for stystolic pressure is 95-135. And the normal range for diastolic pressure is 50-90. When an adult exceeds the normal range, especially the stystolic, they have high blood pressure. which can lead to other complications with the heart and circulatory system. In accordance with the circulatory system, blood has several different aspects as well.

Blood is a crucial key in the body system's proper function and survival. And blood consists of several different functions. The first function is that, "blood is the primary transport medium" (Mader 106). As discussed earlier, blood provides oxygen and nutrients to the cells and removes wastes. The second function is that blood, "...defends the body against invasion of pathogens..." (Mader 106). There are particular blood cells that are designed to protect the body against foreign microbes by processes of phagocytosis and antibody secretion. Both of these processes destroy the pathogens. And the third function is, "blood has regulatory functions" (Mader 107). The blood helps regulate body temperature, liquid content of the blood, and blood pH. There two kinds of cells that make up blood called red and white blood cells.
The red blood cells are produced every second by mitosis inside of bone marrow. They do not have a nucleus or any organelles. Instead, red blood cells are mainly composed of hemoglobin, which is a protein that contains iron in the center of each amino acid chain. The internal space of red blood cells are, "...used for transport of oxygen..." (Mader 108). This occurs when the hemoglobin binds with the oxygen from the lungs. Then, the red blood cells move throughout the capillaries and release the oxygen into the other cells and tissues. Red blood cells also help transport carbon dioxide by allowing the gas to enter the interior of the cell and breaking down the gas with a special enzyme. Then, the blood is sent to the lungs and is released. But, disorders can arise with the involvement of red blood cells, such as sickle-cell anemia. Sickle-cell anemia is a genetic disorder that causes the red blood cells to have a sickle-shaped appearance from, "...a specific amino acid substitute in the hemoglobin..." (www.nslc.wustl.edu/sicklecell/). As these red blood cells pass through the capillaries in the circulatory system, they rupture, causing the appearance of balls underneath the skin in those who are infected. The other kind of cells that make up blood are the white blood cells.
Figure 2: Example of sickle-cell anemia in the bloodstream.


White blood cells, unlike red blood cells, have a nucleus, do not have hemoglobin, are much larger, and are translucent. But, they are produced in the red bone marrow, like red blood cells. White blood cells can be located in the tissue fluid and lymph system due to the occurrence of white blood cells traveling through small pores on the capillaries. Also, white blood cells are a major part of the immune system. They help fight infections by either the process of phagocytosis (engulfing the foreign microbe) or the production of antibodies (a protein that destroys the foreign microbe). There are several types of white blood cells that aid in the destruction of pathogens called: neutrophils, basophils, monocytes, and lymphocytes. The neutrophils are the first type of white blood cells to react to infection by a pathogen. In order for the neutrophils to rid the body of the pathogen, "...they suck up the unwanted substances..." (Mader 110). The basophils release histamine that triggers other cells to act on the invader. The monocytes are macrophages that also rid of pathogens by the process of sucking them up. And they help awaken other defenders of the body to assist in destruction of foreign microbes. And the lymphocytes consist of the T-cells and B-cells that perform the process of specific immunity to destroy pathogens. In accordance with white blood cells, immunity and the immune system has many other aspects as well. Figure 3: The different types of white blood cells such as, neutrophil, basophil, monocytes, and lymphocytes.
As pointed out earlier, the white blood cells aid the immune system in fighting infection. The types of foreign invaders that cause infections in the human body are: bacteria and viruses. Bacteria are independent, prokaryotic cells with their DNA located in the center of the cell. As the bacteria infects the individual, it reproduces by the process of binary fission. In this process, the the DNA within the original bacterial cell is copied. Then, the cell splits into two new bacterial cells that are exact copies of the original. Bacteria causes several diseases such as, strep throat, food poisoning, and tuberculosis. It can also stop cellular metabolism by the release of particular molecules called toxins. Viruses, on the other hand, are not composed of cells and resemble more to the structure of parasites. They can not live independently, but when they enter a host, they reproduce with the aid of particular enzymes and sometimes an RNA genome that are contained within their structure. Viruses cause several diseases such as, the common cold, the flu, and AIDS. In order for immunity to combat diseases produced by bacteria and viruses, it depends on its nonspecific and specific defenses.
Nonspecific defenses consist of the body's, "...built-in barriers, both physical and chemical, that serve as the first line of defense against an infection by pathogens" (Mader 128). For example, mucous membranes located within the respiratory tract try to prevent pathogens entrance by moving the invaders upwards towards the throat. The second line of defense that is used by the nonspecific defenses is the inflammatory response. When an individual has damaged tissue, chemicals are released to alert the neutrophils and macrophages to destroy any invading bacteria that is trying to enter. The external appearance of the individuals body from the inflammatory response will show swelling and redness with pain if pressure is applied to the area. Specific defenses occur when the nonspecific defenses have failed to rid of the infection. Specific defenses occur when it recognizes a cell that is foreign to the body (antigen) by aid of the lymphocytes, such as the B-cells and T-cells. The B-cells and T-cells have specific receptors to unfamiliar cells that are called B-cell receptors (BCR's) and T-cell receptors (TCR's) that allow them to bind to the antigens and rid them by the process of clonal selection. As clonal selection happens with the TCR's, the antigen must be presented to them by another cell in order for the TCR's to recognize it. Then, the TCR's examine the antigen and a normal cell to distinguish which is to be destroyed. The T-cells then multiply with the information as to which cells to kill and finish the process by apoptosis. As clonal selection happens with the BCR's, the antigen is immediately recognized and the BCR's undergo replication with the aid of the T-cells. Then, the B-cells become plasma cells, because, "...they have extensive rough endoplasmic reticulum for the mass production and secretion of antibodies to a specific antigen" (Mader 131). Then, the process is finished when the infection has cleared and apoptosis occurs. Along with T-cells and B-cells, antibodies and macrophages are also very vital to specific defenses.
Antibodies, created by the B-cells, attach to antigens and create an immune complex. It is from this that white blood cells are signaled over to the complex in order for them to rid of the antigen. Macrophages are the most powerful type of phagocytes and can, "...enlist the help of other lymphocytes to carry out specific defense mechanisms" (Mader 129). For example, macrophages play a major role in the process of TCR's clonal selection process by presenting the antigen to the T-cells. Although the immune system is a very strong and powerful force against bacteria and viruses, there is a particular virus, AIDS, that has shut down the power of the immune system completely. Figure 4: Cartoon depicting the process of antibodies. They recognize the foreign invaders, attach to them, and plan to cease and destroy.

The acquired immune deficiency syndrome, or AIDS, is caused by the human immune deficiency virus, or HIV. HIV, "...specifically attacks Helper T-cells and without adequate supply of Helper T-cells, the immune system can not signal B-cells to produce antibodies...to kill infected cells" (www.biology.arizona.edu/immunology/tutorials/AIDS). An individual infected with HIV cannot readily fight off infection, due to the weakening of the immune system, and eventually becomes sick with other types of diseases. When HIV turns into full blown AIDS, an individual, "...develops one or more of a number of opportunistic infections" (Mader 344). These types of infections will be mentioned later. The process for which HIV reproduces can be described by the HIV life cycle. The HIV life cycle occurs in eight steps. The first step is when the HIV attaches to the T-cell's or macrophage's exterior membrane. Then, HIV conjoins with the T-cell or macrophage and enters the interior. The third step is when the HIV releases its nucleic acid of RNA into the cytoplasm of the T-cell or macrophage. Afterwards, the reproductive cycle of HIV, called reverse transcription, occurs. This converts the HIV's RNA to DNA. The fifth step consists of the newly created DNA from the HIV's RNA, enters the nucleus of the cell and combines with the DNA of the cell. This makes the HIV virus part of the cell's DNA information. Then, more of the HIV's RNA is produced, which creates the synthesis of translation. The seventh step is the creation of another viral cell. And lastly, the newly created HIV cell is released from the infected T-cell or macrophage. HIV can also reproduce by certain ways of transmission. HIV can be transmitted by sexual contact, the sharing of intravenous needles with those who are infected, and through blood tranfusions of blood that has been infected by the virus. Also, HIV can be transmitted through bodily fluids such as, "...blood, semen, vaginal fluid, and breastmilk..." (Mader 349). Once an indivdual is infected with the HIV virus and leads to the diagnosis of AIDS, they can also receive other infections such as, pnemonia, cancer of the blood vessels, tuberculosis, parasitic infection of the brain, and cervical cancer. And, unfortunately, these other diseases can actually kill the infected individual than the actual virus itself. The epidemiology of AIDS has shown that all across the globe, AIDS is prevalent everywhere. For example, populations located within Africa and Asia are the largest areas with those who are infected, but each country is on the rise for infection.

The human body is an amazing tool that allows the human race to survive for such an expanded period of time. The four major subjects that make up the complex interworkings of the body are heart and blood vessels, blood, immunity, and AIDS. In the area of the heart and blood vessels, the arteries, capillaries, and veins all worked together in a circular cycle to take blood away from the heart and to the heart. The heart allowed for blood to rid of wastes and provide cells with oxygen and nutrients by the process of a double-pump. And the regulation of blood flow could be determined by the blood pressure from the radial and cartoid arteries. In the subject of blood, the functions in transporting nutrients, defending the body against pathogens, and regulatory patterns, either occured with the assistance of red blood cells or white blood cells. And sometimes, disorders can arise in blood cells such as sickle-cell anemia. In the topic of immunity, foreign invaders such as, bacteria and viruses, can be defeated by nonspecfic or specific defenses. For example, barriers to entry of pathogens, T-cells, B-cells, antibodies, and macrophages. And lastly, the subject that can actually shorten the lifespan of the human race, the virus AIDS. AIDS, which is caused by HIV, can be transmitted several ways and can kill an individual by other means of disease. It is from the understanding of these four subjects that the human race can learn to love and appreciate the tool that they are given to survive.
Sources:
Pictures:
2. medicine.osu.edu/.../index.htm
Works:
1. Human Biology 10e. Mader, Sylvia S.
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