Home About us Products Services Contact us Bookmark
:: wikimiki.org ::
Lymphogranuloma Venereum

Lymphogranuloma venereum

Lymphogranuloma venereum (LGV), also known as lymphopathia venerea, tropical bubo, climatic bubo, strumous bubo, poradenitis inguinales, Durand-Nicolas-Favre disease and lymphogranuloma inguinale, is a sexually transmitted disease caused by the invasive serovars L1, L2, or L3 of Chlamydia trachomatis. LGV was first described by Wallace in 1833 and again by Durand, Nicolas, and Favre in 1913. LGV is primarily an infection of lymphatics and lymph nodes. Chlamydia trachomatis is the bacteria responsible for LGV. It gains entrance through breaks in the skin, or it can cross the epithelial cell layer of mucous membranes. The organism travels from the site of inoculation down the lymphatic channels to multiply within mononuclear phagocytes of the lymph nodes it passes. In the United States, Europe, Australia and most of Asia and South America LGV is generally considered to be a rare disease. Only 42 cases were reported in the US in 2000. The incidence of LGV is on the rise since the early 2000's in homosexual populations. Example, the Netherlands, which typically has fewer than five cases a year, as of September 2004, a total of 92 cases of LGV had been confirmed during the preceding 17 months among men having sex with men. According to the New York State Department of Health, the incidence of LGV is highest among sexually active people living in tropical or subtropical climates, including some areas of the southern U.S. LGV is considered endemic in East and West Africa, India, parts of southeast Asia, South America, and the Caribbean.

Signs and symptoms

Primary stage

LGV may begin as a self-limited painless genital ulcer that occurs at the contact site 3-12 days or longer in this primary stage. Rarely do women notice a primary infection, their inflamed lymph nodes are often deeper (because their infection site and drainage sites are usually different) and not as noticeable, and fewer that 1/3 of men notice as well. This primary stage heals in a few days. Erythema nodosum occurs in 10% of cases.

Secondary stage

The secondary stage occurs from 10-30 days later most often, but has occurred up to 6 months later. The infection is then spread to the lymph nodes through lymphatic drainage pathways. The most frequent presenting clinical manifestation of LGV among males whose primary exposure was genital is unilateral, in 2/3 of cases, lymphadenitis and lymphangitis, often tender inguinal and/or femoral lymphadenopathy because of the drainage pathway for their likely infected areas. Lymphangitis of the dorsal penis may also occur and resembles string or cord. If the route was anal sex or contamination occurred via the fecal-oral route the infected person may experience lymphadenitis and lymphangitis noted above or may have proctitis, inflammation limited to the rectum (the distal 10--12 cm) that may be associated with anorectal pain, tenesmus, or rectal discharge, or proctocolitis, inflammation of the colonic mucosa extending to 12 cm above the anus and is associated with symptoms of proctitis plus diarrhea or abdominal cramps and or inflammatory involvement of perirectal or perianal lymphatic tissues. In females cervicitis, perimetritis, or salpingitis may occur as well as the lymphangitis and lymphadenitis in deeper nodes. Because of lymphatic drainage pathways, some end up with an abdominal mass which seldom suppurates and only 20-30% end up with inguinal lymphadenopathy. Systemic signs: fever, decreased appetite, and malaise, may occur as well. Diagnosis is more difficult in women and homosexual men who may not have the inguinal symptoms. Over the course of the disease, lymph nodes enlarge, enlarged nodes are called buboes, and become painful at first (which may occur in any infection of the same areas as well). The next most common thing is inflammation, thinning and fixation of the overlying skin. Lastly in the progression are necrosis, fluctuant and suppurative lymph nodes, abscesses, fistulas, strictures, and sinus tracts all may occur. During the infection and when it subsides and healing takes place, fibrosis may occur. This can result in varying degrees of lymphatic obstruction, chronic edema, and strictures.

Prognosis

Highly variable. Spontaneous remission is common. Complete cure can be obtained with proper antibiotic treatment. Course is more favorable with early treatment. Bacterial superinfections may complicate course. Death can occur from bowel obstruction or perforation. Follicular conjunctivitis due to autoinoculation of infectious discharge.

Long term complications

Genital elephantiasis or esthiomene ,which is the dramatic end-result of lymphatic obstruction, which may occur because of the strictures themselves, or fistulas. This is usually seen if females, may ulcerate and often occurs 1-20 years after primary infection. Fistulas of, but not limited to, the penis, urethra, vagina, uterus, or rectum. Also, surrounding edema often occurs. Rectal or other strictures and scarring. Systemic spread may occur, possible results are arthritis, pneumonitis, hepatitis, or perihepatitis.

Diagnosis

The diagnosis usually is made serologically (through complement fixation) and by exclusion of other causes of inguinal lymphadenopathy or genital ulcers. Serologic testing is has a sensitivity of 80% after 2 weeks. Serologic testing may not be specific for serotype (has some cross reactivity with other chlamydia species) and can suggest LGV from other forms because of their difference in dilution, 1:64 more likely to be LGV and lower than 1:16 is likely to be other chlamydia forms (emedicine). For idenification of serotypes, culture is often used. Culture is difficult. Requiring a special media, cycloheximide-treated McCoy or HeLa cells, and yields are still only 30-50%. DFA, or direct fluorescent antibody test, PCR of likely infected areas and pus, are also sometimes used. DFA test for the L-type serovar of C trachomatis is the most sensitive and specific test, but is not readily available. If polymerase chain reaction (PCR) tests on infected material are positive, subsequent restriction endonuclease pattern analysis of the amplified outer membrane protein A gene can be done to determine the genotype. It has been noted that one type of testing my not be thorough enough.

Further recommendations

As with all STD's sex partners of patients who have LGV should be examined and tested for urethral or cervical chlamydial infection. After a positive culture for chalamydia, clinical suspicion should be confirmed with testing to distinguish serotype. Antibiotic treatment should be started if they had sexual contact with the patient during the 30 days preceding onset of symptoms in the patient. Patients with a sexually transmited disease need to be tested for other STD's. Antibiotics are not without risks and prophylaxtic broad antibiotic coverage is not recommended.

Treatment

Treatment involves Antibiotics and may involve drainage of the buboes or abscesses by needle aspiration or incision. Further supportive measure may need to be taken: dilatation of the rectal stricture, repair of rectovaginal fistulae, or colostomy for rectal obstruction. Commonly antibiotic treatments include: tetracycline, doxycycline (adults only 2nd to teeth discoloration in children) and erythromycin.

References and external links


- Original article from the public domain resource "1998 Guidelines for Treatment of Sexually Transmitted Diseases" MMWR 47(RR-1);1-118 Publication date: 23 January 1998 at http://wonder.cdc.gov/wonder/prevguid/p0000480/p0000480.asp#head007005000000000 note that this has not been modified since 1998, and may be out of date.
- [http://www.emedicine.com/EMERG/topic304.htm Article on eMedicine.com] Last Updated: 16 October 2004
- Centers for Disease Control and Prevention. Proctitis, proctocolitis, and enteritis. Sexually transmitted diseases treatment guidelines. MMWR Recomm Rep 2002 10 May;51(RR-6):66-7.
- Fitzpatrick's color atlas and synopsis of clinical dermatology 5th ed. Wolff et al.
- Rosen T. Brown: Genital ulcers - evaluation and treatment. Dermatology Clin. 1998;16:673.
- Nederlands tijdschrift voor geneeskunde. vol. 148, no. 51 (18 December 2004): 2544-6.
- Dermatology. vol. 209, no. 3 (2004): 230-2.
- MMWR. Morbidity and mortality weekly report. vol. 53, no. 42 (29 October 2004 ): 985-8.
- International journal of STD & AIDS. vol. 13, no. 6 (2002 Jun): 427-9.
- http://www.essti.org/ Category:Sexually-transmitted diseases

Sexually Transmitted Disease

Sexually transmitted infections (STIs), also known as sexually transmitted diseases (STDs), are diseases that are commonly transmitted between partners through some form of sexual activity, most commonly vaginal intercourse, oral sex, or anal sex. They were commonly known as venereal diseases (VD); Veneris is in Latin the genitive (possessive) form of the name Venus, the Roman goddess of love) until some time around 1990, when public health officials introduced the new term in an effort to improve the clarity of their warnings to the public. Although STD and STI are most often used interchangeably, some make distinctions between the two. As quoted from http://www.etharc.org, "Sometimes the terms STI and STD are used interchangeably. This can be confusing and not always accurate, so it helps first to understand the difference between infection and disease. Infection simply means that a germ – virus, bacteria, or parasite – that can cause disease or sickness is present inside a person’s body. An infected person does not necessarily have any symptoms or signs that the virus or bacteria is actually hurting their body (they do not necessarily feel sick). A disease means that the infection is actually causing the infected person to feel sick, or to notice something is wrong. For this reason, the term STI – which refers to infection with any germ that can cause an STD, even if the infected person has no symptoms – is a much broader term than STD." The distinction being made, however, is closer to that between a "colonization" and an "infection", rather than between an "infection" and a "disease". The term STD refers only to infections that are causing symptoms or problems. Because most of the time, people don’t know they are infected with an STD until they start showing symptoms of disease, most people use the term STD, even though the term STI is also appropriate in many cases. Depending on the STD, a person may or may not still be able to spread the infection if no signs of disease are present. For example, a person is much more likely to spread herpes infection when blisters are present (STD) than when they are absent (STI). However, a person can spread HIV infection (STI) at any time, even if they haven’t developed symptoms of AIDS (STD)." Note that all sexual behaviors that involve contact with another person or the bodily fluids of another person should be considered to contain some risk of transmission of sexually transmitted diseases. Most attention has focused on controlling HIV, which causes AIDS, but each STD presents a different situation. As may be noted from the name, sexually transmitted diseases are transmitted from one person to another by certain sexual activities rather than being actually caused by those sexual activities. Bacteria, fungi, protozoa or viruses are still the causative agents. It is not possible to catch any sexually transmitted disease from a sexual activity with a person who is not carrying a disease; conversely a person who has an STD got it from contact (sexual or otherwise) with someone who had it, or their bodily fluids. Although the likelihood of transmitting various diseases by various sexual activities varies a great deal, in general, all sexual activities between two (or more) people should be considered as being a two-way route for the transmission of STDs (i.e., "giving" or "receiving" are both risky). Health care professionals suggest safer sex, such as the use of condoms in any sexual activity, but safer sex should by no means be considered an absolute safeguard. Abstinence from sexual activities involving other people will protect against sexual transmission of sexually-transmitted infections; however, it must be noted that STDs can also be transmitted through other activities involving transfer of and exposure to bodily fluids, such as blood transfusions and other blood products, sharing injection needles, needle-stick injuries (when medical staff are inadvertently jabbed or pricked with needles during medical procedures), sharing tattoo needles, and childbirth. These means of transmission make certain groups, such as doctors, haemophiliacs and drug users, particularly at risk. Recent epidemiological studies have investigated the networks that are defined by sexual relationships between individuals, and discovered that the properties of sexual networks are crucial to the spread of sexually-transmitted diseases. In particular, assortative mixing between people with large numbers of sexual partners seems to be an important factor. Since prostitutes tend to have large numbers of sexual partners, prostitution without the use of safer sex precautions has often been associated with the spread of sexually transmitted diseases. Some travellers such as truck drivers and sailors also often have high numbers of sexual partners (often prostitutes). However, sexually transmitted diseases are potentially transmitted in any form of sexual relationship, so it is important that all members of the community who are engaged in sexual relationships use safer sex precautions, regardless of the nature of their relationships. It is possible to be an asymptomatic carrier of sexually transmitted diseases. In particular, sexually transmitted diseases in women often cause the serious condition of pelvic inflammatory disease.

Treatment

pelvic inflammatory disease pelvic inflammatory disease Sexually-transmitted diseases have been well-known for hundreds of years — the English language has short words for two of the most common: the "pox" (syphilis) and "the clap" (gonorrhea). Prior to the invention of modern medicines, sexually-transmitted diseases were generally incurable, and treatment was limited to treating the symptoms of the disease. The first venereal diseases clinic opened on January 31, 1747 at London Dock Hospital. The first effective treatment for a sexually-transmitted disease was salvarsan, a treatment for syphilis. With the discovery of antibiotics, a large number of sexually-transmitted diseases became easily curable, and this, combined with effective public health campaigns against STIs, led to a public perception during the 1960s and 1970s that they had ceased to be a serious medical threat. During this period, the importance of contact tracing in treating STIs was recognized. By tracing the sexual partners of infected individuals, testing them for infection, treating the infected and tracing their contacts in turn, STI clinics could be very effective at suppressing infections in the general population. In the 1980s, first genital herpes and then AIDS emerged into the public consciousness as sexually transmitted diseases that could not be cured by modern medicine. AIDS in particular has an asymptomatic period which allowed the disease to be spread to others, followed by a symptomatic period which leads rapidly to death unless treated. Recognition that AIDS threatened a global pandemic led to public information campaigns and the development of treatments that allow AIDS to be managed by suppressing the HIV virus for as long as possible. Contact tracing continues to be an important measure, even when diseases are incurable, as it helps to contain infection. There is now a recognition that safer sex is the most reliable way of decreasing the risk of contracting sexually-transmitted diseases, both curable and incurable. [http://std-gov.org/stds/treatment.htm Current STD Treatment (Cure)]

Types and their causative organisms

Note: All of the diseases on this list can be transmitted sexually. Some of the diseases on this list are commonly transmitted in other ways besides sexually, for example, HIV/AIDS is also commonly transmitted through the sharing of infected needles by drug users, and candidiasis, whilst it can be sexually transmitted, is very often not associated with sexual activity.

Bacterial


- Chancroid (Haemophilus ducreyi)
- Chlamydia infection (Chlamydia trachomatis)
- Donovanosis (Granuloma inguinale or Calymmatobacterium granulomatis)
- Gonorrhea (Neisseria gonorrheae)
- Lymphogranuloma venereum (LGV) (Chlamydia trachomatis serotypes L1, L2, L3. See Chlamydia)
- Non-gonococcal urethritis (NGU) (Ureaplasma urealyticum or Mycoplasma hominis)
- Syphilis (Treponema pallidum)

Viral


- Cytomegalovirus
- Hepatitis (Hepatitis A and Hepatitis E are transmitted via the fæcal-oral route, not sexually; Hepatitis C is probably not sexually transmittable)
  - Hepatitis B
  - Hepatitis D
- Herpes /HSV (Herpes simplex virus)
- Human Immunodeficiency Virus (HIV/AIDS)
- Human papillomavirus (HPV)
  - Certain strains of HPV cause genital warts
  - Certain strains of HPV cause cervical dysplasias which can lead to cervical cancer

Parasites


- Pubic lice a.k.a "crabs"(Phthirius pubis)
- Scabies (Sarcoptes scabiei)

Fungal


- Candidiasis (thrush) (Candida albicans) is not strictly an STD but can be transmitted through sexual contact

Protozoal


- Amoebiasis (Entamoeba histolytica)
- Giardiasis (Giardia lamblia)
- Trichomoniasis (Trichomonas vaginalis)

See also


- Vulvovaginal disorders
- Transmission (medicine)

External links


- [http://www.arhp.org/healthcareproviders/resources/stdis/index.cfm Sexually Transmitted Diseases/Infections Resource Center from the Association of Reproductive Health Professionals]
- [http://www.niaid.nih.gov/publications/stds.htm Fact sheet on sexually transmitted diseases from the National Institute of Allergies and Infections]
- [http://powerlaws.media.mit.edu/papers/liljeros03.pdf "Sexual networks: implications for the transmission of sexually transmitted infections"]
- [http://www.stdhelper.com/ Sexually Transmitted Disease Information]
- [http://std-gov.org Sexually Transmitted Diseases - STD Guide] ja:性行為感染症

Chlamydia trachomatis

Chlamydia trachomatis is a species of the chlamydiae, a group of obligately intracellular bacteria. It causes chlamydia, a sexually transmitted disease, and trachoma, an eye infection that is a frequent cause of blindness. It is one of the smallest of all bacteria and its size may be as small as 500 nm in width, not much bigger than the largest viruses.

External link


- [http://www.gpnotebook.co.uk/cache/342556674.htm Chlamydia trachomatis] - GP Notebook Category:Chlamydiae

Lymph nodes

Lymph nodes are components of the lymphatic system. Clusters of lymph nodes are found in the underarms, groin, neck, chest, and abdomen. Lymph nodes act as filters, with an internal honeycomb of connective tissue filled with lymphocytes that collect and destroy bacteria and viruses. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. The spleen and tonsils are large lymphoid organs that serve similar functions, though the spleen does not filter lymph but blood. Lymph nodes are bean-shaped and range in size from a few millimeters to about 1-2 cm in their normal state. They may become enlarged due to a tumor or infection. The lymph node is surrounded by a fibrous capsule, and inside the lymph node the fibrous capsule extends to form trabeculae. Thin reticular fibers form a supporting meshwork inside the node. The concave side of the lymph node is called the hilum. The artery and vein attach at the hilum and allow blood to enter and leave the organ, respectively. The parenchyma of the lymph node is divided into an outer cortex and an inner medulla. The cortex is absent at the hilum. The cortex contains several oval-shaped lymphoid nodules (also called follicles) which are aggregates of lymphocytes contained within a meshwork of supporting cells. Nodules that consist mainly of small lymphocytes are called primary nodules. Nodules called secondary nodules are those that contain a pale central region called a germinal center. The germinal center forms (and thus a primary nodule becomes a secondary nodule) when a B cell that has recognized an antigen undergoes proliferation, differentiates into plasma cells, and forms antibodies. The band of the cortex adjacent to the medulla is the deep cortex, also called the juxtamedullary cortex or paracortex. This layer is devoid of nodules. Formation of the deep cortex depends on the migration of T cells. Thus it is sometimes also called the thymus-dependent cortex. In comparison, the layer of the cortex that contains nodules is called the nodular cortex. The medulla consists of cords of lymphatic tissue (medullary cords) separated by vessel-like spaces called medullary sinuses. Lymph travels to the lymph node via afferent lymphatic vessels and drains into the node just beneath the capsule in a space called the subcapsular sinus. The subcapsular sinus drains into trabecular sinuses and finally into medullary sinuses. The sinus space is criss-crossed by the pseudopods of macrophages which act to trap foreign particles and filter the lymph. The medullary sinuses converge at the hilum and lymph then leaves the lymph node via the efferent lymphatic vessel. Lymphocytes, both B cells and T cells, constantly circulate through the lymph nodes. They enter the lymph node via the bloodstream and may cross the wall of the bloodvessel by the process of diapedesis. The B cells migrate to the nodular cortex and medulla, and the T cells migrate to the deep cortex. When a lymphocyte recognizes an antigen, B cells become activated and migrate to germinal centers. When antibody-producing plasma cells are formed, they migrate to the medullary cords antigen

Lymph nodes of the head and neck

Anterior Cervical

These nodes, both superficial and deep, lie above and beneath the sternocleidomastoid muscles. They drain the internal structures of the throat as well as part of the posterior pharynx, tonsils, and thyroid gland.

Posterior Cervical

These nodes extend in a line posterior to the sternocleidomastoids but in front of the trapezius, from the level of the mastoid bone to the clavicle. They drain the skin on the back of the head. They are frequently enlarged during upper respiratory infections.

Tonsilar

These nodes are located just below the angle of the mandible. They drain the tonsilar and posterior pharyngeal regions.

Sub-mandibular

These nodes run along the underside of the jaw on either side. They drain the structures in the floor of the mouth.

Sub-mental

These nodes are just below the chin. They drain the teeth and intra-oral cavity.

Supraclavicular

These nodes are in the hollow above the clavicle, just lateral to where it joins the sternum. They drain a part of the thoracic cavity and abdomen. Virchow's node is a left supraclavicular lymph node which receives the lymph drainage from most of the body (especially the abdomen) via the thoracic duct and is thus an early site of metastasis for various malignancies.

See also


- Adenitis Category:Lymphatic system ja:リンパ節

Epithelial

In zootomy, epithelium is a tissue composed of a layer of cells. Epithelium can be found lining internal (e.g., endothelium, which lines the inside of blood vessels) or external (e.g., skin, cornea) free surfaces of the body. The outermost layer of our skin is composed of dead squamous epithelial cells, as are the mucous membranes lining the inside of mouths and body cavities. Other epithelial cells line the insides of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, and make up the exocrine and endocrine glands. Functions of epithelial cells include secretion, absorption and protection. Epithelial cells sit on a basal lamina (formerly called a basement membrane). "Neuroepithelium" refers to epithelial tissue that has sensory nerve endings.

Classification

Epithelial cells are classified by the following three factors: -
- Shape
- Stratification (number of layers)
- Specialization

Shape


- Squamous: Squamous cells are flat cells with an irregular flattened shape. The one-cell layer of simple squamous epithelium is a minimal barrier to diffusion. Places where squamous cells can be found include the alveoli of the lungs, the filtration of the kidneys, and the major cavities of the body. These cells are relatively inactive metabolically, and are associated with the diffusion of water, electrolytes, and other substances.
- Cuboidal: As the name suggests, these cells have a shape similar to a cube, meaning its width is the same size as its height. The nuclei of these cells are usually located in the center.
- Columnar: Simple columnar epithelium is made up of a single layer of cells that are longer than they are wide. The nucleus is also closer to the base of the cell. The small intestine is a tubular organ lined with this type of tissue. Unicellular glands called goblet cells are scattered throughout the simple columnar epithelial cells and secrete mucus. The free surface of the columnar cell has tiny hairlike projections called microvilli. They increase the surface area for absorption.

Stratification


- Simple: There is a single layer.
- Stratified: More than one layer of cells. The superficial layer is used to classify the layer. Only one layer touches the basal lamina. Stratified cells can usually withstand large amounts of stress.
- Pseudostratified with cilia: This is used mainly in one type of classification (pseudostratified columnar epithelium). There is only a single layer of cells, but the position of the nuclei gives the impression that it is stratified. If a specimen looks stratified, but you can identify cilia, the specimen is pseudostratified ciliated epithelium since stratified epithelium cannot have cilia.
- Transitional: This is a specialized type of epithelium found lining organs that can stretch, such as the bladder or the ureter of mammals. Since the cells can slide over each other, the appearance of this epithelium depends on whether the organ is distended or contracted: if distended, it appears as if there are only a few layers; when contracted, it appears as if there are several layers.

Specialization


- Keratinization / Cornification: Cells contain keratin (a cytoskeletal protein). This process occurs mainly in skin, since it provides a tough, impermeable barrier.
- Ciliated: See Cilia
- Brush border / Microvilli: See Microvilli. These are found in cells that play an absorptive role since they greatly increase the surface area. Found in intestine and kidney tubules.
- Stereocilia: Similar to cilia, except they have no internal structure and are non-motile. Found in vas deferens and epididymis.

Examples


- Simple squamous: Found in blood vessels & lymph channels (called endothelium) and body cavities (called mesothelium)
- Keratinized stratified squamous: Found in human skin (specifically, the dead superficial layer)
- Stratified squamous: Found in human oesophagus
- Simple cuboidal: Found in thyroid follicles
- Stratified cuboidal: Exclusively found in sweat gland ducts
- Ciliated simple columnar: Found in intestine and kidney (specifically, distal convoluted tubule)
- Stratified columnar: Ducts of submandibular glands
- Transitional: Specialized to distend (stretch) as the urinary bladder fills

Junctional complexes

See junctional complex

Secretory epithelia

As stated above, secretion is one major function of epithelial cells. Glands are formed from the invagination / infolding of epithelial cells and subsequent growth in the underlying connective tissue. There are two major classification of glands: endocrine glands and exocrine glands. Category:Tissues ja:上皮細胞

United States

:For alternative meanings, see the disambiguation page for US, USA, United States, or American. The United States of America is a federal democratic republic situated primarily in central North America. It comprises 50 states and one federal district, and has several territories. It is also referred to, with varying formality, as the United States, the U.S., the U.S.A., the States, or simply and most commonly, America. The official founding date of the United States is July 4, 1776, when the Second Continental Congress—representing thirteen British colonies—adopted the Declaration of Independence. However, the structure of the government was profoundly changed in 1788, when the states replaced the Articles of Confederation with the United States Constitution. The date on which each of the fifty states adopted the Constitution is typically regarded as the date that state "entered the Union" (became part of the United States). Since the mid-20th century, following World War II, the United States has emerged as a dominant global influence in economic, political, military, scientific, technological, and cultural affairs.

Geography and climate

The United States shares land borders with Canada (to the north) and Mexico (to the south), and territorial water boundaries with Canada, Russia, the Bahamas, and numerous smaller nations. It is otherwise bounded by the Pacific Ocean and the Bering Sea, in the west; the Arctic Ocean, in the northernmost areas; and the Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea, in the eastern and southeastern areas. Forty-eight of the states are in the single region between Canada and Mexico; this group is referred to, with varying precision and formality, as the continental or contiguous United States, sometimes abbreviated CONUS, and as the Lower 48. Alaska, which is not included in the term contiguous United States, is at the northwestern end of North America, separated from the Lower 48 by Canada. The archipelago of Hawaii is in the Pacific Ocean. The capital city, Washington, District of Columbia is a federal district located on land donated by the state of Maryland. (Virginia also donated land, but it was returned in 1847.) The United States also has overseas territories with varying levels of independence and organization. When inland water is included in the total area, only Russia and Canada are larger than the United States; if inland water is excluded, China ranks third and the U.S. ranks fourth. The United States' total area is 3,718,711 square miles (9,631,418 km²), of which land makes up 3,537,438 square miles (9,161,923 km²) and water makes up 181,273 square miles (469,495 km²). The United States' landscape is one of the most varied among those of the world's nations: among its many features are temperate forestland and rolling hills, on the east coast; mangrove, in Florida; the Great Plains, in the center of the country; the Mississippi–Missouri river system; the Great Lakes, four of the five of which are shared with Canada; the Rocky Mountains, west of the Great Plains; deserts and temperate coastal zones, west of the Rocky Mountains; and temperate rain forests, in the Pacific northwest. Alaska's tundra, and the volcanic, tropical islands of Hawaii add to the geographic diversity. Hawaii The climate varies along with the landscape, from tropical in Hawaii and southern Florida to tundra in Alaska and atop some of the highest mountains. Most of the North and East experience a temperate continental climate, with warm summers and cold winters. Most of the South experiences a subtropical humid climate with mild winters and long, hot, humid summers. Rainfall decreases markedly from the humid forests of the Eastern Great Plains to the semi-arid shortgrass prairies on the high plains abutting the Rocky Mountains. Arid deserts, including the Mojave, extend through the lowlands and valleys of the southwest, from westernmost Texas to California and northward throughout much of Nevada. Some parts of California have a Mediterranean climate. Rainforests line the windward mountains of the Pacific Northwest from Oregon to Alaska.

History

American history started with the migration of people from Asia across the Bering land bridge approximately 12,000 years ago following large animals that they hunted into the Americas. These Native Americans left evidence of their presence in petroglyphs, burial mounds, and other artifacts. It is estimated that 2-9 million people lived in the territory now occupied by the U.S. before European contact, and the subsequent introduction of foreign diseases such as small pox that greatly diminished the native populations. Some advanced societies were the Anasazi of the southwest, who inhabited Chaco Canyon, and the Woodland Indians, who built Cahokia, located near present-day St Louis, a city with a population of 40,000 at its peak in AD 1200. Vikings first visited North America around 1000, but did not settle permanently. Following the discovery voyages of Christopher Columbus around 1492, other Europeans began to explore and settle there. During the 1500s and 1600s, the Spanish settled parts of the present-day Southwest and Florida, founding St. Augustine, Florida in 1565 and Santa Fe (in what is now New Mexico) in 1607. The first successful English settlement was at Jamestown, Virginia, also in 1607. Within the next two decades, several Dutch settlements, including New Amsterdam (the predecessor to New York City), were established in what are now the states of New York and New Jersey. In 1637, Sweden established a colony at Fort Christina (in what is now Delaware), but lost the settlement to the Dutch in 1655. This was followed by extensive British settlement of the east coast. The British colonists remained relatively undisturbed by their home country until after the French and Indian War, when France ceded Canada and the Great Lakes region to Britain. Britain then imposed taxes on the 13 colonies, widely regarded by the colonists as unfair because they were denied representation in the British Parliament. Tensions between Britain and the colonists increased, and the thirteen colonies eventually rebelled against British rule. British Parliament, George Washington (1789-1797).]] In 1776, the 13 colonies split from Great Britain and formed the United States, the world's first constitutional and democratic federal republic, after their Declaration of Independence of that year, and the Revolutionary War (1775 to 1783). The original political structure was a confederation in 1777, ratified in 1781 as the Articles of Confederation. After long debate, this was supplanted by the Constitution in 1789, forming a more centralized federal government. Prior to all these was the Albany Congress in 1754, in which a union was first seriously proposed. From early colonial times, there was a shortage of labor, which encouraged unfree labor, particularly indentured servitude and slavery. In the mid-19th century, a major division occurred in the United States over the issue of states' rights and the expansion of slavery. The northern states had become opposed to slavery, while the southern states saw it as necessary for the continued success of southern agriculture and wanted it expanded to the territories. Several federal laws were passed in an attempt to settle the dispute, including the Missouri Compromise and the Compromise of 1850. The dispute reached a crisis in 1861, when seven southern states seceded1 from the Union and formed the Confederate States of America, leading to the Civil War. Soon after the war began, four more southern states seceded. During the war, Abraham Lincoln issued the Emancipation Proclamation, mandating the freedom of all slaves in states in rebellion, though full emancipation did not take place until after the end of the war in 1865, the dissolution of the Confederacy, and the Thirteenth Amendment took effect. The Civil War effectively ended the question of a state's right to secede, and is widely accepted as a major turning point after which the federal government became more powerful than state governments. Thirteenth Amendment). The title of the painting, from a 1726 poem by Bishop Berkeley, was a phrase often quoted in the era of Manifest Destiny, expressing a widely held belief that civilization had steadily moved westward throughout history. [http://americanart.si.edu/t2go/1lw/1931.6.1.html (more)] ]] During the 19th century, many new states were added to the original 13 as the nation expanded across the continent. Manifest Destiny was a philosophy that encouraged westward expansion in the United States. As the population of the Eastern states grew and as a steady increase of immigrants entered the country, settlers moved steadily westward across North America. In the process, the U.S. displaced most American Indian nations. This displacement of American Indians continues to be a matter of contention in the U.S. with many tribes attempting to assert their original claims to various lands. In some areas American Indian populations were reduced by foreign diseases contracted through contact with European settlers, and US settlers acquired those emptied lands. In other instances American Indians were removed from their traditional lands by force. Though some would say the U.S. was not a colonial power until the Spanish-American War when it acquired Puerto Rico, Guam and the Philippines, the dominion exercised over land in North America the United States claimed is essentially colonial. The Philippines became independent in 1946. During this period, the nation also became an industrial power. This continued into the 20th century, which has been termed "the American Century" because of the nation's overriding influence on the world. The US became a center for innovation and technological development; major technologies that America either developed or was greatly involved in improving include the telephone, television, computer, the Internet, nuclear weapons, nuclear power, aviation, and aeronautics. In addition to the Civil War, another major traumatic experience for the nation was the Great Depression (1929 to 1939). The nation has also taken part in several major foreign wars, including World War I and World War II (in both of which the US later joined the Allies). During the Cold War, the US was a major player in the Korean War and Vietnam War, and, along with the Soviet Union, was considered one of the world's two "superpowers". With the collapse of the Soviet Union, the US emerged as the world's leading economic and military power. Beginning in the 1990s, the United States became very involved in police actions and peacekeeping, including actions in Kosovo, Haiti, Somalia and Liberia, and the first Persian Gulf War driving Iraq out of Kuwait. After attacks on the World Trade Center and the Pentagon on September 11, 2001, the United States and other allied nations found themselves involved in what has come to be called the "War on Terrorism," which has primarily encompassed military actions in both Afghanistan and Iraq.

Government

Iraq of the United States.]]

Republic and suffrage

The United States is an example of a constitutional republic, with a government composed of and operating through a set of limited powers imposed by its design and enumerated in the United States Constitution. Specifically, the nation operates as a presidential democracy. There are three levels of government: federal, state, and local. Officials of each of these levels are either elected by eligible voters via secret ballot or appointed by other elected officials. Americans enjoy almost universal suffrage from the age of 18 regardless of race, sex, or wealth. There are some limits, however: felons are disenfranchised and in some states former felons are likewise. Furthermore, the national representation of territories and the federal district of Washington, DC in Congress is limited: residents of the District of Columbia are subject to federal laws and federal taxes but their only Congressional representative is a non-voting delegate.

Federal government

The federal government is the national government, comprising the Legislative Branch (led by Congress), the Executive Branch (led by the President), and the Judicial Branch (led by the Supreme Court). These three branches were designed to apply checks and balances on each other. The Constitution limits the powers of the federal government to defense, foreign affairs, the issuing and management of currency, the management of trade and relations between the states, and the protection of human rights. In addition to these explicitly stated powers, the federal government—with the assistance of the Supreme Court—has gradually extended these powers into such areas as welfare and education, on the basis of the "necessary and proper" clause of the Constitution.

The Congress

necessary and proper The Congress of the United States is the legislative branch of the federal government of the United States. It is bicameral, comprising the House of Representatives and the Senate. The House of Representatives consists of 435 members, each of whom represents a congressional district and serves for a two-year term. House seats are apportioned among the states by population; in contrast, each state has two Senators, regardless of population. There are a total of 100 senators, who serve six-year terms. The powers of Congress are limited to those enumerated in the Constitution; all other powers are reserved to the states and the people. The Constitution also includes the necessary-and-proper clause, which grants Congress the power to "make all laws which shall be necessary and proper for carrying into execution the foregoing powers."

The President

necessary-and-proper clause At the top level of the executive branch is the President of the United States. The President and Vice-President are elected as 'running mates' for four-year terms by the Electoral College, for which each state, as well as the District of Columbia, is allocated a number of seats based on its representation (or ostensible representation, in the case of D. C.) in both houses of Congress (see U.S. Electoral College). The relationship between the President and the Congress reflects that between the English monarchy and parliament at the time of the framing of the United States Constitution. Congress can legislate to constrain the President's executive power, even with respect to his or her command of the armed forces; however, this power is used only very rarely—a notable example was the constraint placed on President Richard Nixon's strategy of bombing Cambodia during the Vietnam War. The President cannot directly propose legislation, and must rely on supporters in Congress to promote his or her legislative agenda. The President's signature is required to turn congressional bills into law; in this respect, the President has the power—only occasionally used—to veto congressional legislation. Congress can override a presidential veto with a two-thirds majority vote in both houses. The ultimate power of Congress over the President is that of impeachment or removal of the elected President through a House vote, a Senate trial, and a Senate vote. The threat of using this power has had major political ramifications in the cases of Presidents Andrew Johnson, Richard Nixon, and Bill Clinton. The President makes around 2,000 executive appointments, including members of the Cabinet and ambassadors, which must be approved by the Senate; the President can also issue executive orders and pardons, and has other Constitutional duties, among them the requirement to give a State of the Union address to Congress once a year. Although the President's constitutional role may appear to be constrained, in practice, the office carries enormous prestige that typically eclipses the power of Congress: the Presidency has justifiably been referred to as 'the most powerful office in the world'. The Vice President is first in the line of succession, and is the President of the Senate ex officio, with the ability to cast a tie-breaking vote. The members of the President's Cabinet are responsible for administering the various departments of state, including the Department of Defense, the Justice Department, and the State Department. These departments and department heads have considerable regulatory and political power, and it is they who are responsible for executing federal laws and regulations. George W. Bush is the 43rd President, currently serving his second term.

The Courts

George W. Bush The highest court is the Supreme Court, which consists of nine justices. The court deals with federal and constitutional matters, and can declare legislation made at any level of the government as unconstitutional, nullifying the law and creating precedent for future law and decisions. Below the Supreme Court are the courts of appeals, and below them in turn are the district courts, which are the general trial courts for federal law. Separate from, but not entirely independent of, this federal court system are the individual court systems of each state, each dealing with its own laws and having its own judicial rules and procedures. A case may be appealed from a state court to a federal court only if there is a federal question; the supreme court of each state is the final authority on the interpretation of that state's laws and constitution.

State and local governments

supreme court of each state. Note that Alaska and Hawaii are shown at different scales, and that the Aleutian Islands and the uninhabited Northwestern Hawaiian Islands are omitted from this map.]] The state governments have the greatest influence over people's daily lives. Each state has its own written constitution and has different laws. There are sometimes great differences in law and procedure between the different states, concerning issues such as property, crime, health, and education. The highest elected official of each state is the Governor. Each state also has an elected legislature (bicameral in every state except Nebraska), whose members represent the different parts of the state. Of note is the New Hampshire legislature, which is the third-largest legislative body in the English-speaking world, and has one representative for every 3,000 people. Each state maintains its own judiciary, with the lowest level typically being county courts, and culminating in each state supreme court, though sometimes named differently. In some states, supreme and lower court justices are elected by the people; in others, they are appointed, as they are in the federal system. The institutions that are responsible for local government are typically town, city, or county boards, making laws that affect their particular area. These laws concern issues such as traffic, the sale of alcohol, and keeping animals. The highest elected official of a town or city is usually the mayor. In New England, towns operate directly democratically, and in some states, such as Rhode Island and Connecticut, counties have little or no power, existing only as geographic distinctions. In other areas, county governments have more power, such as to collect taxes and maintain law enforcement agencies.

Political divisions

With the Declaration of Independence, the thirteen colonies proclaimed themselves to be nation states modeled after the European states of the time. Although considered as sovereigns initially, under the Articles of Confederation of 1781 they entered into a "Perpetual Union" and created a fully sovereign federal state, delegating certain powers to the national Congress, including the right to engage in diplomatic relations and to levy war, while each retaining their individual sovereignty, freedom and independence. But the national government proved too ineffective, so the administrative structure of the government was vastly reorganized with the United States Constitution of 1789. Under this new union, the continued status of the individual states as sovereign nation states fell into dispute in 1861, as several states attempted to secede from the union; in response, then-President Abraham Lincoln claimed that such secession was illegal, and the result was the American Civil War. Since the Union victory in 1865, the independent status of the individual states has not been broached again by any state, and the status of each state within the union has been deemed by mainstream officials and academics to be settled as being subordinate to the union as a whole. In subsequent years, the number of states grew steadily due to western expansion, the purchase of lands by the national government from other nation states, and the subdivision of existing states, resulting in the current total of 50. The states are generally divided into smaller administrative regions, including counties, cities and townships. The United States–Canadian border is the longest undefended political boundary in the world. The U.S. is divided into three distinct sections:
- the "continental United States," also known as "the Lower 48" and more accurately termed the conterminous, coterminous or contiguous United States
- Alaska, which is physically connected only to Canada
- the archipelago of Hawaii, in the central Pacific Ocean. The United States also holds several other territories, districts, and possessions, notably the federal district of the District of Columbia, which is the nation's capital, and several overseas insular areas, the most significant of which are American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands. The Palmyra Atoll is the United States' only incorporated territory; it is unorganized and uninhabited. The United States Navy has held a base at a portion of Guantanamo Bay, Cuba, since 1898. The United States government possesses a lease to this land, which only mutual agreement or United States abandonment of the area can terminate. The present Cuban government of Fidel Castro disputes this arrangement, claiming Cuba was not truly sovereign at the time of the signing. The United States argues this point moot because Cuba apparently ratified the lease post-revolution, and with full sovereignty, when it cashed one rent check in accordance with the disputed treaty.

Foreign relations and military

sovereign] The immense military and economic dominance of the United States has made foreign relations an especially important topic in its politics, with considerable concern about the image of the United States throughout the world. Reactions towards the United States by other nationalities are often strong, ranging from uninhibited admiration and mimicking of all things American to anti-Americanism. US foreign policy has swung about several times over the course of its history between the poles of strict isolationism and imperialism and everywhere in between. Three of the nation's four military branches are administered by the Department of Defense: the Army, the Navy (including the Marine Corps), and the Air Force. The Coast Guard falls under the jurisdiction of the Department of Homeland Security in peacetime, but is placed under the Department of the Navy in time of war. The combined United States armed forces consist of 1.4 million active duty personnel, along with several hundred thousand each in the Reserves and the National Guard. Military conscription ended in 1973. The United States Armed forces are considered to be the most powerful military (of any sort) on Earth and their force projection capabilities are unrivaled by any other nation. The 2005 defense budget amounted to $401.7 billion, which is an increase of 4% over 2004 and of 35% since 2001. Over 50% of that number is spent in research & development. (For comparison, in 2004 the European Union (considered as the second-largest military force) had a combined total of 1.6 million troops, and a defense budget of €160 billion, with less than 10% of that being spent on R&D.)

Largest cities

The United States has dozens of major cities, including 11 of the 55 global cities of all types — with three "alpha" global cities: New York City, Los Angeles, and Chicago. The figures expressed below are for populations within city limits. A different ranking is evident when considering U.S. metro area populations, although the top three would be unchanged. Note that some cities not listed (such as Atlanta, Boston, Las Vegas, Miami, Nashville, New Orleans, Seattle, and Washington, D.C.) are still considered important on the basis of other factors and issues, including culture, economics, heritage, and politics. The twenty largest cities, based on the United States Census Bureau's 2004 estimates, are as follows:

Economy

The United States has the largest single-country economy in the world, with a per-capita gross domestic product of $40,100. In this market-oriented economy, private individuals and business firms make most of the decisions, and the federal and state governments buy needed goods and services predominantly in the private marketplace. gross domestic product The largest industry of the U.S. is now service, which employs roughly three quarters of the U.S. work force. The United States has many natural resources, including oil and gas, metals, and such minerals as gold, soda ash, and zinc. In agriculture, the U.S. is a top producer of, among other crops, corn, soy beans, and wheat; the United States is a net exporter of food. The U.S. manufacturing sector produces goods such as, cars, airplanes, steel, and electronics, among many others. Economic activity varies greatly from one part of the country to another, with many industries being largely dependent on a certain city or region; New York City is the center of the American financial, publishing, broadcasting, and advertising industries; Silicon Valley is the country’s primary location for high-technology companies, while Los Angeles is the most important center for film production. The Midwest is known for its reliance on manufacturing and heavy industry, with Detroit, Michigan, serving as the center of the American automotive industry; the Great Plains are known as the "breadbasket" of America for their tremendous agricultural output; the intermountain region serves as a mining hub and natural gas resource; the Pacific Northwest for fish and timber, while Texas is largely associated with the oil industry; the Southeast is a major hub for both medical research and the textiles industry. Several countries continue to link their currency to the dollar or even use it as a currency (such as Ecuador), although this practice has subsided since the collapse of the Bretton Woods system. Many markets are also quoted in dollars, such as those of oil and gold. The dollar is also the predominant reserve currency in the world, and more than half of global reserves are in dollars. The largest trading partner of the United States is Canada (19%), followed by China (12%), Mexico (11%), and Japan (8%). More than 50% of total trade is with these four countries. In 2003, the United States was ranked as the third most visited tourist destination in the world; its 40,400,000 visitors ranked behind France's 75,000,000 and Spain's 52,500,000. Labor unions have existed since the 19th century, and grew large and powerful from the 1930s to the 1950s. See Labor history of the United States. Since 1970 they have shrunk in the private sector and now cover fewer than 8% of the workers. However union membership has grown rapidly in the public sector, especially among teachers, nurses, police, postal workers, and municipal clerks. There have been few strikes in recent years. The United States' imports exceed exports by 80%, leading to an annual trade deficit of $700,000,000,000, or 6% of gross domestic product. It is the largest debtor nation in the world, with total gross foreign debt of over $13,000,000,000,000 (2005 estimate); and it absorbs more than 50% of global savings annually. Since the 1980s, the U.S. has increased the use of neoliberal economic policies that reduce government intervention and reduce the size of the welfare state, backing away from the more interventionist Keynsian economic policies that had been in favor since the Great Depression. As a result, the United States provides fewer government-delivered social welfare services than most industrialized nations, choosing instead to keep its tax burden lower and relying more heavily on the free market and private charities. Sixteen states and the District of Columbia have minimum wages higher than the national level ($5.15 per-hour), including the highest, Washington State at $7.35. Twenty-six states are the same as the federal level; two--Ohio and Kansas--are below; and six do not have state laws. America's wealth is relatively highly concentrated. The average C.E.O. earns 500 times the typical amount a worker grosses, this is up from 25 times in the late 1970s. In terms of wealth the top 1% of Americans own 40% of all assets and 50.1% of the country's income goes to the top twenty percent of households. Average wages for the majority of employees have been largely stagnating since the 1970s. America's poverty line defined as a family of four earning less than $19,157 is at 12.7% of the general population. Approximately one out of every five children in the United States grows up below the official poverty line. Among racial groups; African Americans have the lowest median income while Asians had the highest. Regionally, the southern states had the lowest median incomes while the West Coast and New England had the highest. The current Federal Reserve Chairman Alan Greenspan remarked that the U.S.’s growing income inequality since the 1970s is, "not the type of thing which a democratic society - a capitalist democratic society - can really accept without addressing."[http://www.csmonitor.com/2005/0614/p01s03-usec.html?s=itm] However, Greenspan also noted, "...you can look at the system and say it's got a lot of problems to it, and sure it does. It always has. But you can't get around the fact that this is the most extraordinarily successful economy in history."

Transportation

Alan Greenspan ]] Because the United States is a relatively young nation, most of the development of U.S. cities has taken place since the invention of the automobile. To link its vast territory, the United States built a network of high-capacity, high-speed highways, of which the most important element is the Interstate Highway system, commissioned in the 1950s by President Dwight D. Eisenhower and modeled after the German Autobahn. The United States also has a transcontinental rail system, which is used for moving freight across the lower forty-eight states. Passenger rail service is provided by Amtrak, which serves forty-six of the lower forty-eight states. Many cities in the United States have extensive mass-transit systems. New York City operates one of the world's largest and most heavily used subway systems. The regional rail and bus networks that extend into Long Island, New Jersey, Upstate New York, and Connecticut are among the most heavily used in the world. Air travel is often preferred for destinations over 300 miles (500 kilometers) away. In terms of passengers, seventeen of the world's thirty busiest airports in 2004 were in the U.S., including the world's busiest, Hartsfield-Jackson Atlanta International Airport; in terms of cargo, in the same year, twelve of the world's thirty busiest airports were in the U.S., including the world's busiest, Memphis International Airport. There are several major seaports in the United States; the three busiest are the Port of Los Angeles, California; the Port of Long Beach, California; and the Port of New York and New Jersey. Others include Houston, Texas; Charleston, South Carolina; Savannah, Georgia; Miami, Florida; Portland, Oregon; San Francisco, California; Boston, Massachusetts; Philadelphia, Pennsylvania; and Seattle, Washington; plus, outside the contiguous forty-eight states, Anchorage, Alaska, and Honolulu, Hawaii.

Society

Demographics

Hawaii The mean center of the U.S. population continues to drift farther west and south. The fastest growing region is the western United States followed by the southern portion. According to Census 2000, the states that saw the greatest increases from 1990 were: Nevada (66.3%), Arizona (40%), Colorado (30.6%), Utah (29.6%), Idaho (28.5%), Georgia (26.4%), Florida (23.5%), Texas (22.8%), North Carolina (21.4%), and Washington (21.1%). [http://www.census.gov/population/cen2000/phc-t2/tab03.pdf]

Ethnicity and race

:Main article: Racial demographics of the United States The United States is a very racially diverse country. According to the 2000 census, it has 31 ethnic groups with at least one million members each, and numerous others represented in smaller amounts. The majority of Americans descend from white European immigrants who arrived at the establishment of the first colonies (most after Reconstruction). This majority--69.1% in 2000--decreases each year, and is expected to become a plurality within a few decades. The most frequently stated European ancestries are German (15.2%), Irish (10.8%), English (8.7%), Italian (5.6%) and Scandinavian (3.7%). Many immigrants also hail from Slavic countries such as Poland and Russia. Other significant immigrant populations came from eastern and southern Europe and French Canada. Russia Hispanics from Mexico and South and Central America are the largest minority group in the country, comprising 12.5% of the population (2000 census). People of Mexican descent made up 7.3% of the population in the 2000 census, and this proportion is expected to increase significantly in the coming decades. About 12.3% (2000 census) of the American people are African Americans (Blacks). African Americans are spread throughout the country, but their presence is largest in the South. Asian Americans--including Native Hawaiians and Pacific Islanders--are a third significant minority (3.7% of the population in 2000). Most Asian Americans are concentrated on the West Coast and Hawaii. The largest groups are immigrants or descendants of emigrants from the Philippines, China, India, Vietnam, South Korea, and Japan. Indigenous peoples in the United States, such as American Indians and Inuit, make up 0.9% of the population (2000 census). About 35% live on Indian reservations.

Religion

Polls estimate that just under 80 percent of Americans are Christians of various denominations. The other 20 percent comprises other religions such as Hinduism, Judaism, Islam, and Buddhism, other various faiths, and those without a specific religion. The United States is noteworthy among developed nations for its relatively high level of religiosity. According to a 2004 Gallup poll, about 44% of Americans attend a religious service at least once a week. However, this rate is not uniform across the country; attendance is more common in the Bible Belt—composed largely of Southern and Midwestern states—than in the Northeast and West Coast. In the Southern states, Baptists are the largest group, followed by Methodists; Roman Catholics are dominant in the Northeast and in large parts of the Midwest due to their being settled by descendants of Catholic immigrants from Europe (such as Germany, Ireland, Italy, and Poland) or other parts of North America (mainly Quebec and Puerto Rico). The rest of the country for the most part has a complex mixture of various Christian groups.

Education

West Coast's home at Monticello and the University of Virginia (library building shown above, and designed by Jefferson), the only collegiate campus on the list. Both sites are located in Charlottesville, Virginia.]] In the United States, education is a state, not federal, responsibility, and the laws and standards vary considerably. However, the federal government, through the Department of Education, is involved with funding of some programs and exerts some influence through its ability to control funding. In most states, all students must attend mandatory schooling starting with kindergarten, which children normally enter at age 5, and following through 12th grade, which is normally completed at age 18

Disease

A disease is any abnormal condition of the body or mind that causes discomfort, dysfunction, or distress to the person affected or those in contact with the person. Sometimes the term is used broadly to include injuries, disabilities, syndromes, symptoms, deviant behaviors, and atypical variations of structure and function, while in other contexts these may be considered distinguishable categories. Pathology is the study of diseases. The subject of systematic classification of diseases is referred to as nosology. The broader body of knowledge about diseases and their treatments is medicine.

Syndromes, illness and disease

Medical usage sometimes distinguishes a disease, which has a known specific cause or causes (called its etiology), from a syndrome, which is a collection of signs or symptoms that occur together. However, many conditions have been identified, yet continue to be referred to as "syndromes". Furthermore, numerous conditions of unknown etiology are referred to as "diseases" in many contexts. Illness, although often used to mean disease, can also refer to a person's perception of their health, regardless of whether they in fact have a disease. A person without any disease may feel unhealthy and believe he has an illness. Another person may feel healthy and believe he does not have an illness even though he may have a disease such as dangerously high blood pressure which may lead to a fatal heart attack or stroke.

Transmission of disease

Some diseases, such as influenza, are contagious or infectious, and can be transmitted by any of a variety of mechanisms, including droplets from coughs and sneezes, by bites of insects or other vectors, from contaminated water or food, etc. Other diseases, such as cancer and heart disease are not considered to be due to infection, although micro-organisms may play a role.

Social significance of disease

The identification of a condition as a disease, rather than as simply a variation of human structure or function, can have significant social or economic implications. The controversial recognitions as diseases of post-traumatic stress disorder, also known as "shell shock"; repetitive motion injury or repetitive stress injury (RSI); and Gulf War syndrome has had a number of positive and negative effects on the financial and other responsibilities of governments, corporations and institutions towards individuals, as well as on the individuals themselves. The social implication of viewing aging as a disease could be profound, though this classification is not yet widespread. A condition may be considered to be a disease in some cultures or eras but not in others. Oppositional-defiant disorder, attention-deficit hyperactivity disorder, and, increasingly, obesity are conditions considered to be diseases in the United States and Canada today, but were not so-considered decades ago and are not so-considered in some other countries. Conversely, the number of people in the West who consider homosexuality to be a disease became widespread in the 20th century but has been decreasing in the last two decades. To consider a condition to be a disease can sometimes involve a negative social value judgement. Lepers were a group of afflicted individuals who were historically shunned and the term "leper" still evokes social stigma. Fear of disease can still be a widespread social phenomena, though not all diseases evoke extreme social stigma.

Other uses of the term

In biology, disease refers to any abnormal condition of an organism that impairs function. The term disease is often used metaphorically for disordered, dysfunctional, or distressing conditions of other things, as in disease of society.

See also


- List of childhood diseases
- List of common diseases
- List of diseases for a huge list of 6000+ diseases, many very rare.
- List of genetic disorders
- List of environment topics
- Diagnosis
- Epidemic
- Illness
- Palliative care
- Therapy
- Transmission

External links


- [http://www.nlm.nih.gov/medlineplus/healthtopics.html Health Topics], MedlinePlus descriptions of most diseases, with access to current research articles.
- [http://www.cdc.gov/health/default.htm Center for Disease Control Health Topics A-Z], fact sheets about many common diseases
- [http://rarediseases.about.com/ Rare/Orphan Diseases]
- [http://www.national-health.org/rarediseases/ National Organization for Rare Disorders] Extensive, useful information on rare diseases.
- [http://www.merck.com/pubs/mmanual/sections.htm The Merck Manual], detailed description of most diseases, freely searchable online. Category:Diseases Category:Medical terms als:Krankheit zh-min-nan:Pīⁿ ms:Penyakit ja:病気 simple:Disease th:โรค



Tropics

The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the northern hemisphere and the Tropic of Capricorn in the southern hemisphere. This area lies approximately between 23°30'/23.5° N latitude and 23°30'/23.5° S latitude, and includes all the parts of the Earth where the sun reaches a point directly overhead at least once during the solar year. (In the temperate zones, north of the Tropic of Cancer and south of the Tropic of Capricorn, the sun never reaches an altitude of 90° or directly overhead.) The word "tropics" comes from Greek tropos meaning "turn", because the apparent position of the Sun oscillates between the two tropics with a period that defines the average length of a year. Tropical plants and animals are those species native to the tropics. Tropical is also sometimes used in a general sense of a place that is warm and moist year-round, often with the sense of lush vegetation. However, there are places in the tropics that are anything but "tropical" in this sense, with even alpine tundra and snow-capped peaks, including Mauna Kea, Mt. Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina. In Köppen's scheme of climate classification, a tropical climate is defined as a non-arid climate in which all twelve months have mean temperatures above 18 °C (64.4 °F).

Examples of tropical cities


- Bombay, India (19.1º N)
- Hong Kong, Hong Kong SAR, People's Republic of China (22.3º N)
- Rio de Janeiro, Brazil (22.9º S)
- Singapore (1.4º N)
- Manila, Philippines (14.6º N)
- Cairns, Queensland, Australia (16.7º S)

See also


- Subtropical
- Tropical year
- Tropical disease Category:Climate ko:열대 ja:熱帯 zh-min-nan:Jia̍t-tài

Subtropics

The subtropics (also known as semitropics) are the geographic regions of the Earth immediately north and south, respectively, of the two tropics: the Tropic of Cancer and the Tropic of Capricorn—i.e. above 23.5° N latitude and below 23.5° S latitude. The term is not well-defined but it implies a range of latitudes between 23.5 and approximately 35 degrees. A subtropical climate implies that the screen temperature normally does not dip below 0°C. This is a threshold temperature for a wide gamut of plants. This applies to coastal California, southern Florida, coastal Australia, and coastal South Africa, for instance. The poleward limit is higher on the west coast of the northern continents and less on the east, because occasional cold snaps in winter reach further south in the east. Beyond that the climate is called temperate, i.e. annual mean temperatures are less than 20°C while the warmest month averages over 10°C. (E. Linacre 12/98) ----

Ulcer

An ulcer (from Latin ulcus) is an open sore of the skin, eyes or mucous membrane, often caused by an initial abrasion and generally maintained by an inflammation and/or an infection.

Description

Ulcers are non-healing wounds that develop on the skin, mucous membranes or eye. Although they have many causes, they are marked by: # Loss of integrity of the area # Secondary infection of the site by bacteria, fungus or virus # Generalized debilitation of the patient # A lengthy healing time

Skin ulcers

The skin is the largest organ of the human body. Classification systems are used to communicate the severity and depth of an ulcer. It is an easy way to communicate changes for the better, or worse.

Merck Manual classification


- Stage 1: The skin is red. The underlying tissue is soft. The redness disappears with minor pressure.
- Stage 2: There is redness, swelling and hardening of the skin around the area. Sometimes there is blistering. Sometimes there is loss of the superficial skin.
- Stage 3: The skin becomes necrotic. There may be exposure of the fat beneath the skin. The skin may be lost through all its layers.
- Stage 4: There is more loss of fat and more necrosis of the skin through to the muscle beneath.
- Stage 5: Continuing loss of fat and necrosis of muscle below.
- Stage 6: Bone destruction begins with irritation of the bone, erosion of the bone cortex progressing to osteomyelitis. There may be sepsis of a joint, pathologic fracture or generalized body infection, septicemia.

National Pressure Ulcer Advisory Panel (NPUAP)


- Stage I - There is erythema of intact skin which does not blanch with pressure. It may be the heralding lesion of skin ulceration.
- Stage 2 - There is partial skin loss involving the epidermis, dermis, or both. The ulcer is superficial and presents as an abrasion, blister, or wound with a shallow center.
- Stage 3 - This is an entire thickness skin loss. It may involve damage to or necrosis of subcutaneous tissue that may extend down to underlying fascia. The ulcer presents as a deep crater with or without undermining of adjacent intact tissues.
- Stage 4 - Here there is entire thickness skin loss with extensive destruction, tissue necrosis, or damage to muscle, bone, or supporting structures. Tendons, and joints may also be exposed or involved. There may be undermining and holes or sinus tracts associated with ulcers at this stage.

Wagner's classification


- Grade 0 - Skin with prior healed ulcer scars, areas of pressure which are sometimes called pre-ulcerative lesion or the presence of bony deformity which puts pressure on an unguarded point.
- Grade I - A The wound is superficial in nature, with partial or full-thickness skin involvement but does not include tendon, capsule or bone.
- Grade I-B - As above, the wound is superficial in nature, with partial or full thickness skin involvement but not including tendon, capsule nor bone; however the wound is infected. The definition of this wound implies superficial infection without involvement of underlying structures. If the wound shows signs of significant purulence or fluctuance, further exploration to expose a higher grade classification of infection is in order.
- Grade I-C - As above but with vascular compromise.
- Grade I-D - As above but with ischemia. Because ischemia is a type of vascular compromise, the distinction between these two grades is often difficult to make.
- Grade 2-A - Penetration through the subcutaneous tissue exposing tendon or ligament, but not bone.
- Grade 2-B - Penetration through the deep tissues including tendon or ligament and even joint capsule but not bone.
- Grade 2-C - As above 2B, but including ischemia
- Grade 2-D - As above 2c, but including infection
- Grade 3-A - A wound which probes to bone but shows no signs of local infection nor systemic infection.
- Grade 3-B - A wound which probes to bone and is infected
- Grade 3-C - A wound which probes to bone is infected and is ischemic.
- Grade 3-D - A wound which probes to bone characterized by active infection, ischemic tissues and exposed bone.
- Grade 4 - Gangrene of the forefoot
- Grade 5 - Gangrene of the entire foot

Other locations