Hypotension and Hypertension

Force originating in the pumping action of the heart, exerted by the blood against the walls of the blood vessels; the stretching of the vessels in response to this force and their subsequent contraction are important in maintaining blood flow through the vascular system. In human beings, blood pressure is usually measured indirectly over the brachial or femoral artery: the highest (systolic) pressure, normally about 120 (100 to 140) millimeters of mercury, occurs during contraction of the ventricles; the lowest (diastolic) pressure, normally about 80 (60 to 100) millimeters, occurs during ventricular relaxation. Blood pressure in the capillaries is usually about 20 to 30 millimeters, while the pressure in the large veins may become negative (lower than atmospheric pressure). Hypertension occurs when the body's smaller blood vessels (the arterioles) narrow, causing the blood to exert excessive pressure against the vessel walls and forcing the heart to work harder to maintain the pressure. Although the heart and blood vessels can tolerate increased blood pressure for months and even years, eventually the heart may enlarge (a condition called hypertrophy) and be weakened to the point of failure. Injury to blood vessels in the kidneys, brain, and eyes also may occur. Extensive bleeding is an obvious cause of reduced blood volume that leads to hypotension. There are other possible causes. A person who has suffered an extensive burn loses blood plasma blood minus the red and white blood cells and the platelets. Blood volume is reduced in a number of conditions involving loss of salt and water from the tissues as in excessive sweating and diarrhea and its replacement with water from the blood. Loss of water from the blood to the tissues may result from exposure to cold temperatures. Also, a person who remains standing for as long as one-half hour may temporarily lose as much as 15 percent of the blood water into the tissues of the legs.

Cancer

Group of more than 100 distinct diseases characterized by the uncontrolled growth of abnormal cells in the body. Cancer affects one in every three persons born in developed countries and is a major cause of sickness and death throughout the world. Though it has been known since antiquity, significant improvements in cancer treatment have been made since the middle of the 20th century, mainly through a combination of timely and accurate diagnosis, selective surgery, radiation therapy, and chemotherapeutic drugs. Such advances actually have brought about a decrease in cancer deaths. The billions of cells that make up a tumor are descended from a single cell that has found a way to escape the normal controls of its growth. This loss of control is caused by damage of the genetic material in the cell, specifically the long, coiled chains of deoxyribonucleic acid (DNA) found in the chromosomes. Such damage can arise during cell division, be induced by environmental agents, or be inherited. Regardless of how the damage is caused, genetic changes and the abnormal growth pattern that they promote are passed on to a cell's progeny (its daughter cells) as the cell divides. Important determinant of the way a tumor will grow how fast it will give rise to clinical symptoms, and how early it may be diagnosed. For example, a tumor of the skin located on the face is usually detected very early, whereas a sarcoma located in the deep soft tissues of the abdomen can grow to weigh 2 kilograms before it causes much of a disturbance. The site of origin of a tumor also determines the signs and symptoms of disease that the individual will experience and influences possible therapeutic options. The most common tumor sites in females are the breast, lung, and colon. In men the most frequently affected sites are the prostate, lung, and colon. Cancer is to a great degree a disease of the elderly, and age is thus a very important factor in cancer development. However, individuals of any age, including very young children, can be stricken with the disease. Benign and malignant tumors produce a number of effects in an individual that vary depending on the location of the tumor, the tumor’s functional activity, and any acute events that occur as the tumor mass grows and evolves. Metastatic tumors (those that result from the spread of the primary tumor) can produce the same consequences. A tumor affects normal bodily functions by compressing, invading, and destroying normal tissues and also by producing substances that circulate in the bloodstream .In order for cancer to be diagnosed as early as possible, an individual should be aware of symptoms that may be related to the disease. The standard diagnostic workup begins with a detailed clinical history of the person. A complete physical examination, including laboratory tests such as a complete blood count and a urinalysis, is made. Diagnostic imaging using X-ray, ultrasound, computed tomography (CT) scans, or magnetic resonance imaging(MRI) may be essential, and radioisotopes can be used to visualize certain organs or regions of the body.

Hepatitis

There are seven known hepatitis viruses, which are labeled A, B, C, D, E, F, and G. Hepatitis A, E, and F viruses are transmitted through the ingestion of contaminated food or water (called the fecal-oral route); the spread of these agents is aggravated by crowded conditions and poor sanitation. The B, C, D, and E viruses are transmitted mainly by blood or bodily fluids; sexual contact or exposure to contaminated blood are common modes of transmission The signs and symptoms of acute viral hepatitis result from damage to the liver and are similar regardless of the hepatitis virus responsible. Patients may experience a flulike illness, and general symptoms include nausea, vomiting, abdominal pain, fever, fatigue, loss of appetite, and, less commonly, rash and joint pain. The onset of hepatitis A usually occurs 15 to 45 days after exposure to the virus, and some infected individuals, especially children, exhibit no clinical manifestations. In the majority of cases, no special treatment other than bed rest is required; most recover fully from the disease. Hepatitis A does not give rise to chronic hepatitis. The severity of the disease can be reduced if the affected individual is injected within two weeks of exposure with immune serum globulin obtained from persons exposed to hepatitis A virus. This approach, called passive immunization, is effective because the serum contains antibodies against hepatitis A virus. Hepatitis B may occur as an acute disease, or, in about 5 to 10 percent of cases, the illness may become chronic and lead to permanent liver damage. Symptoms usually appear from 40 days to 6 months after exposure to the hepatitis B. Those persons at greatest risk for contracting hepatitis B include intravenous drug users, sexual partners of individuals with the disease, health care workers who are not adequately immunized, and recipients of organ transplants or blood transfusions. A safe and effective vaccine against HBV is available and provides protection for at least five years. Passive immunization with Symptoms of hepatitis C usually appears within six to nine weeks after exposure. Hepatitis C virus appears to be transmitted in a manner similar to hepatitis B virus. Hepatitis C has a greater propensity than hepatitis B to develop into chronic liver disease. Alcoholics who are infected with hepatitis C are more prone to develop cirrhosis. Infection with hepatitis D virus may occur at the same time infection with hepatitis B virus occurs, or hepatitis D virus may infect a person already infected with hepatitis B virus. The latter situation appears to give rise to a more serious condition, leading to cirrhosis or chronic liver disease. Alpha interferon is the only treatment for hepatitis D virus infection. Preventing infection with hepatitis B virus also prevents hepatitis D virus infection. Hepatitis E virus is transmitted in the same manner as hepatitis B virus, and it, too, only causes acute infection. However, the effects of infection with hepatitis E virus are more severe than those caused by hepatitis A virus, and death is more common. The risk of acute liver failure from infection with hepatitis E virus is especially great for pregnant women. In less-developed countries, including Mexico, India, and those in Africa, hepatitis E virus is responsible for widespread epidemics of hepatitis that occur as a result of ingestion of contaminated water or food enteric transmission.

AIDS

HIV has been found in Chimpanzees in western equatorial Africa. This virus, known as simian immunodeficiency virus (SIV), does not readily cause disease in chimpanzees. However, AIDS is a Zoonosis, an infection that is shared by humans and lower vertebrate animals. The practice of hunting, butchering, and eating the meat of chimpanzees may have allowed transmission of the virus to humans, probably in the late 19th century or early 20th century. Genetic studies of a pandemic strain of HIV, known as HIV-1 group M, have indicated that the virus emerged between 1884 and 1924 in central and western Africa. Researchers estimate that this strain of the virus began spreading throughout these areas in the late 1950s. Later, in the mid-1960s, an evolved strain called HIV-1 group M subtype B spread from Africa to Haiti. In Haiti this subtype acquired unique characteristics, presumably through the process of genetic recombination. Sometime between 1969 and 1972, the virus migrated from Haiti to the United States. The virus spread within the United States for about a decade before it was discovered in the early 1980s. The worldwide spread of HIV-1 was likely facilitated by several factors, including increasing urbanization and long-distance travel in Africa, international travel, changing sexual mores, and intravenous drug use. In 1981 investigators in New York and California reported the first official case of AIDS. Initially, most cases of AIDS in the United States were diagnosed in homosexual men, who contracted the virus primarily through sexual contact, and in intravenous drug users, who became infected mainly by sharing contaminated hypodermic needles HIV is transmitted by the direct transfer of bodily fluids, such as blood and blood products, semen and other genital secretions, or breast milk, from an infected person to an uninfected person. The primary means of transmission worldwide is sexual contact with an infected individual. HIV frequently is spread among intravenous drug users who share needles or syringes. Prior to the development of screening procedures and heat-treating techniques that destroy HIV in blood products, transmission also occurred through contaminated blood products; many people with hemophilia contracted HIV in this way. Today the risk of contracting HIV from a blood transfusion is extremely small. In rare cases transmission to health care workers may occur by an accidental stick with a needle used to obtain blood from an infected person Tests for the disease check for antibodies to HIV, which appear from four weeks to six months after exposure. The most common test for HIV is the enzyme linked immunosorbent assay (ELISA). If the result is positive, the test is repeated on the same blood sample. Another positive result is confirmed using a more specific test such as the Western blot. A problem with ELISA is that it produces false positive results in people who have been exposed to parasitic diseases such as malaria; this is particularly troublesome in Africa, where both AIDS and malaria are rampant As with any epidemic for which there is no cure, tragedy shadows the disease's advance The United Nations designated December 1 as World Aids Day.