integumentary system

integumentary system

SKIN

The body needs a special protection or integumentary system to protect it from the constant attacks coming from the external environment. The forms of aggression to which the organism is exposed are multiple and diverse source (solar radiation, temperature, shock, pathogens).

The skin is a major organ or membranous sheet that covers the entire outer surface of the body separating the individual from the external environment and defending their attacks.

skin functions

- The skin is the residence of the sense of touch receptors

- Complies with protection functions, is an effective barrier to microbial penetration,

has antibacterial and antifungal acid pH and the fatty acids of their secretions neutralized solar radiation by the pigments contained therein.

- Prevents loss of water and electrolytes, excretory acts as removing waste organic metabolism, gases and other substances exchanged lipoprotein.

- Contributes to the regulation of temperature by vasodilation and sweating or insensible perspiration.

Specific layers of the skin, also contain other three cell types:

melanocytes (skin pigmentation)

The lapiel important endogenous pigment is "melanin." Producing cells

are melanin and dendritic melanocytes.

The precursors of these cells arise from neural crest and migrate during prenatal life to the limit

of the epidermis to the dermis, fixed in the site or in the basal layer of the epidermis and differentiate

in melanocytes.

Melanocytes are located below the stratum germinativum cells or between them, have long

dendritic which extend between the basal layer cells.

The most important function of epidermal melanin is to protect cells from layers

depth of the epidermis and the underlying dermis, against the harmful effects of ultraviolet light

excess, for which disperses the latter. The effect of UV light is beneficial to some

point as it causes a form of vitamin D, but too much has carcinogenic effects.

Langerhans cells

Langerhans cells are scattered throughout the epidermis, but localized

mainly in the stratum spinosum.

These cells are also called dendritic cells for numerous long extensions.

They are found also in the dermis, as in the stratified epithelia of the drawings

oral cavity, esophagus, vagina.

The light microscope these cells show a dense core, pale cytoplasm and extensions

long thin radiating from the cell body into the intercellular spaces between cells

epithelial (keratinocytes).

Electron microscopy reveals that the nucleus is polymorphic, cytoplasm electronlucent home

few mitochondria, RER and no intermediate filament short but contains lysosomes, bodies

multivesicular and small vesicles.

The more characteristic aspect of these cells is the presence of Birbeck granules, limited by

membrane, no function has been identified.

These cells originate from bone marrow precursors, but are capable of entering mitosis

is restricted to them this activity, therefore, continuously restore precursor cells

leave the blood to migrate to the epidermis and differentiate into Langerhans cells.

These cells function in the immune response. Have cell surface receptors for Fc

(antibody) and C3 (complement) and phagocytose foreign antigens and disintegrate.

Langerhans cells migrate to lymph nodes in the neighborhood, which present

epitopes of foreign agents undergoing processing to T cells are thus cells

antigen presenters.

merkel cells

Are interspersed among the keratinocytes of the basal layer of the epidermis. It remains unclear origin.

  Although usually found as single cells oriented in parallel with the basal lamina, can extend their processes between keratinocytes, to which are connected by desmosomes.

The nuclei are deeply indented and three types of cytokeratins

within the cytoplasm are the cytoskeletal filaments. Contents present inside dense granules located in the perinuclear region and in the

extensions whose function is unclear. There unmyelinated sensory nerves passing through the basal lamina and approaching to the cells

Merkel to form complexes with Merkel cells and axons. It is possible that these complexes function as mechanoreceptors.

skin diseases

Acute contact dermatitis (irritant or allergic).

The acute contact dermatitis eczema may be caused hundreds of chemicals, plants and photoreactive agents irritants and sensitizers. Most dermatoses

professionals can be classified as allergic dermatitis acute eczematous contact. Clinical signs are heat, redness, swelling, blistering and oozing. The patients suffer from itching, burning and discomfort general. The backs of the hands and the inside of the wrists and the forearms are the most frequently affected sites, although contact dermatitis may appear at any point of the skin. If the dermatitis appears on the front, eyelids, ears,

Subacute contact dermatitis

Using a cumulative effect, repeated exposure to irritants can cause weak and moderate a subacute contact dermatitis characterized by the appearance of plaques red and dry. If exposure continues, the dermatitis becomes chronic.

                                          Contact dermatitis chronic eczematous

If a contact dermatitis relapse over a prolonged period of time is called chronic eczematous contact dermatitis. The areas most commonly affected by chronic eczematous lesions are the hands, fingers, wrists and forearms, the affected skin is red, dry and is scaly

Photosensitivity dermatitis (phototoxic or photoallergic)

Most photoreactions on the skin are phototoxic source. Artificial light sources or natural, alone or combined with various chemicals, plants or drugs, may induce photosensitivity or phototoxic response. The phototoxic reaction is usually limited to areas exposed to light, while the photosensitivity reaction usually develops in unexposed surfaces

Folliculitis and acneiform dermatoses

including chloracne People who perform their work in dirty conditions often develop lesions involving the follicular orifices. Comedones (blackheads) may be the only obvious effect of exposure but also secondary infections often occur in the follicle. The problem may also worsen if personal hygiene and grooming habits are inadequate. Follicular lesions usually appear on the forearms and, less frequently, thighs and buttocks, but they can occur anywhere, except in the palms of the hands and soles of the feet

Reactions induced by the sweat

Many jobs involve exposure to heat, if heat and sweating are excessive and insufficient follow evaporation of sweat from the skin, can cause a rash. If the affected area is eroded by rubbing a skin surface to another, are often bacterial or fungal

granulomas

In many jobs granulomas can occur if the right circumstances. Occupational exposure to bacteria, fungi, viruses or parasites can cause granulomas. Substances such as bone fragments, wood chips, charcoal, coral rubble or gravel and minerals such as beryllium, silica and zirconia can also cause granulomas after embedded in the skin.

ulcerative changes

Ulcerative action is demonstrated in the following chemicals: chromic acid, potassium dichromate concentrated, arsenic trioxide, calcium oxide, calcium nitrate and calcium carbide.

The main areas affected are the fingers and palm creases and cracks. Several of these agents also produce nasal septum perforation.

Chemical or thermal burns, wounds or contusions bacterial or fungal infections can cause ulcerative excavation of the affected part

viral infections

Viral diseases are the group most common infectious diseases in childhood, and its very common skin symptoms. It should also be remembered that in the first years of life there is a special predisposition to these infections in relation to the immunological immaturity of both humoral and cellular. Skin lesions can be caused by the virus itself, which may be isolated or, conversely, the clinical skin is the result of interaction with the immune system, as in the case of most rash diseases. We should note also that the lesions are nodular or vesicular which may contain the virus and potentially infectious.

SKIN DISEASES BY

HERPES SIMPLEX VIRUS

etiology

Skin infections with HSV are most common viral diseases. They are DNA viruses belonging to the family Herpesviridae exclusively human reservoir and usually cause vesicular lesions in clusters with erythematous edematous base, often accompanied by a satellite adenopathy.

SKIN DISEASES BY

Human Papillomavirus (HPV)

Approximately, between 7 and 10% of the population present at some point common warts, reaching 20% in children of school age, reaching a peak frequency between 12 and 16. The frequency is increased in case of immunosuppression. More rare is the appearance of genital warts in children, we always should be suspected sexual abuse.

SKIN DISEASES poxvirus

The molluscum contagious virus (CMV) is the largest known virus. The course of infection is usually self-limited, we must individually evaluate the appropriateness of treatment

The infection occurs worldwide but is most common in tropical and subtropical regions, probably due to greater inherent scaling hydration. Epidemiological studies suggest that is related to poor hygiene and climatic factors such as heat and humidity

Physical findings are usually limited to the skin, but have been reported cases that affect eyelids and conjunctiva. It usually appears as a para-

pulas small (usually 2-6 mm, but may vary from 1 to 15), dome-shaped. Can not change color over normal skin, or appear as white or yellowish translucent

herpes zoster

VZV remains throughout life in the sensory ganglia after the primary infection. When beyond the control of the immune system appears herpes zoster.

Herpes zoster (HZ) is a viral skin manifested by pain nerve and a vesicular rash distributed in the peripheral territory innervation of a sensory ganglion (metamer). Is caused by varicella zoster virus (VZV), viral DNA of 90 Kd. Infection with this virus usually occurs from contact by air and, in non-immune causes chickenpox

bacterial infection

PATHOGENESIS OF INFECTION

BACTERIAL SKIN

It involves three main factors.

A. - Pathogenicity of the organism: It is determined by:

a) The invasiveness, antifagocitarios dependent components of the surface.

b) The properties of the microorganism toxigenic. some

species have the ability to multiply and invade tissues profusely through a resistance to phagocytic action. Others have toxigenic properties of the lesion responsible local or systemic manifestations of a local infection. Local invasiveness is an important factor in streptococcal pharyngitis, but the clinical manifestations of scarlet fever are the result of the development of erythrogenic toxin

- Entrance doors: The way in which microorganisms reach

the zone of injury will determine the character of the cutaneous inflammatory response to certain bacteria, the vascular wall is the first site of cutaneous involvement when infection is bacteremic, the initial manifestation is bleeding or thrombosis with infarction, followed by tissue reaction observed with the direct incubation of the skin.

CLASSIFICATION

Several classifications may be of bacterial infections

skin, these vary according to the source studied.

The dermatologic literature the most commonly classified into primary, secondary and tertiary; infectious literature classifies them according to the causative agent, others according to the potential severity and skin structure

affected. When divided into primary, secondary and tertiary, we have:

A. - Primary: This is one in which the infection itself, represents the

injury and is not associated with other skin disease or systemic bacterial infection.

2. - Secondary: This is one in which a preexisting skin disease is aggravated by infection added. When the number of organisms colonizing the skin injured increase at 10 6 / ml or more, bacteria can act as pathogens creating additional inflammation.

3. - Tertiary: Skin lesions resulting from systemic bacterial infection.

fungal infections

The fungi that cause mycoses in humans are in two states: yeasts and molds. A yeast fungus can be defined as comprising a single cell, while the molds are fungi with many cells of filamentous structure. The cells of fungi have little or nothing to do with those of other germs that cause infections, being more nearly related, though far behind, with plants with bacteria. By this, the products used to treat fungal lesions or have little to do with the antibiotics used to treat other infections.

The same disorder, such as infections of the nails or onychomycosis, can be produced by different groups of fungi. Also important are the ecological and environmental factors, to the definition which are responsible for the infection.

 Tubs

- Tinea capitis or scalp: areas appear hairless and scaly, sometimes with pustules and crusts. Sometimes the injury smells of ammonia.

- Tinea barbae or beard and mustache: follicular Small abscesses in the area of ​​the beard and mustache.

- Tinea corporis: In areas of hairless skin, regions of the trunk, abdomen, arms, legs and face. The lesions are circular with red borders and scaly, itchy and grow out. There are different ways with inflammation variable.

- Tinea cruris: In the groin, a red, scaly plaque, which causes itching, blisters on the edges. This form is more common in the adult male.

- Tinea manum: On the palms of the hands and fingers edges scaly plaques and vesicles with or without thickening of the skin. They can be an eczema-like lesions of contact.

- Tinea pedis: On the soles and the spaces between the toes. The lesions are scaly, itchy, and cracks in the bottom of the folds of the spaces between the fingers, especially in the fourth space. It is also called athlete's foot, as it relates to sweating when wearing athletic shoes.

- Tinea unguium or ringworm of the nails.

- Pityriasis versicolor

It is characterized by lesions similar to bran, with more or less color than the skin on that seat, located on the trunk, especially in the shoulders and back. The appearance of the lesions is related to factors of the individual, since the fungus is a commensal that is normally inhabits the skin of healthy people. These factors that favor its appearance is related to a replacement of the outer layers of the skin slower than usual.

- Candidiasis

The Candida yeasts usually infect large folds under the breasts and English, causing the so-called intertrigo. It also results as eczema pictures of diapers, or nail infections that are common in people who often have wet hands, as waiters, sometimes accompanied by inflammation in the skin around the nail.

infection by parasites

A parasite is an organism, such as a one-celled animal (protozoan) or worm, that survives dwelling within another organism, usually larger (the host).

Parasitic infections are common in rural Africa, Asia and South America but are rare in developed countries. However, those living in developed countries and visit other developing can become infected by parasites and return home unaware that carry the disease, which can be difficult to diagnose because it is very rare.

The worms usually enter the body through the mouth, although some do it through the skin. Those that infect the intestine may stay there or penetrate the intestinal wall and infect other organs. The worms usually do so through the skin through the soles of the feet, or enter the body when the person anything in infected waters.

amebiasis

amebiasis

In addition to ulcers in the colon, amoebae can cause abscesses in different organs, of which the most frequently affected is the liver.

Amebiasis is an infection of intestine caused by Entamoeba histolytica, a unicellular parasite.

Entamoeba histolytica exists in two forms during its life cycle: active parasite (trophozoite) and the inactive parasite (cyst). Trophozoites live between intestinal contents and feed on bacteria or gut wall. When you start the infection, the trophozoites can cause diarrhea, which makes getting in and out of the body. Once outside, the fragile trophozoites die. When the patient does not have diarrhea, they often become cysts before leaving the intestine. The cysts are very hardy and can be spread both directly from person to person, and indirectly through food or water.

giardiasis

Giardiasis is an infection of the small intestine caused by Giardia lamblia, a unicellular parasite.

Giardiasis occurs worldwide and is especially common among children and in places where sanitation is poor. In some developed countries, giardiasis is one of the most common intestinal parasitic infections. It is more common among gay men and who have traveled to developing countries. It is also more common among people who have low stomach acid, to those who have been surgically removed, in those with chronic pancreatitis and in people whose immune system is weak.

trichinosis

Trichinosis is a parasitic infection caused by Trichinella spiralis.

Trichinosis is present in most of the world, but is rare or absent in areas where pigs are fed with root vegetables, as in France. In the United States, has become infrequent.

Infection occurs by eating pork or pork products, raw, undercooked or badly processed. In rare cases, infection can be acquired from eating bear meat, wild boar and some marine mammals. Any of these animals may contain a cyst of the larvae (trichinae). When the cyst capsule is digested in the stomach or duodenum, releasing larvae that penetrate the wall of the small intestine. In the course of 2 days, the larvae mature and mate. Male worms are no longer involved in the production of infection. Females remain nested within the intestinal wall and the seventh day live larvae begin to download.

trichinosis

Aspect of Trichinella spiralis, female and male. The female (left) contains larvae inside. On the right (box), appearance of a cyst in a muscle.

Each female can produce over 1 000 larvae. Production continues for 4 to 6 weeks, after which the female dies and is digested. The tiny larvae are transported throughout the body through the lymphatic vessels and blood flow. Which survive only manage to reach skeletal muscle. Penetrate them and cause inflammation. At the end of the third month encyst.

ankylostomiasis

Hookworm infection is caused by an intestinal worm either Ancylostoma duodenale or Necator americanus.

About a quarter of the world population is infected with these worms with hooks. The infection is common in warm, moist areas where sanitation is poor. The Ancylostoma duodenale is found in the Mediterranean, India, China and Japan, Necator americanus is typical of tropical Africa, Asia and the Americas.

Hookworm Lifecycle duodenal

In the life cycle of each worm, the eggs are discharged in the feces and mature in the ground after being incubated for one or two days. A few days later, larvae hatch and live on earth. An individual can become infected by walking barefoot in an area contaminated by human feces and the larvae penetrate the skin.