Words about skin WORDS ABOUT SKIN A DNA Deoxyribonucleic acid located in the nucleus of each cell. DNA is structured in a double helix, and is the support of the genetic information. Amino-acid Small molecule of 10 to 15 atoms, the basic component of the proteins of all living things. 20 in number, they join together in chains to form the protein. As an illustration they might be compared with the letters of the alphabet which are the building blocks of our writing system. Fatty Acid Organic acid, a major constituent of lipids. A fatty acid has a long hydrocarbon chain and a terminal carboxyl group. Acne Acne is a skin disorder involving the sebaceous gland. The canal leading from this gland becomes blocked leading to the formation of spots. Male hormones play a significant role in triggering acne. Surfactants Chemical molecules capable of enhancing wetting by water (such as detergents and soaps). Albinism A genetic illness characterised by the absence of melanin pigments in the skin and hair. Androgens Male hormone which in particular regulate the appeance and the development of the male charcteristics (e.g.

testosterone) Antifungal agent A substance destroying the fungi and yeast-like organisms responsible for mycosis. Antigen Any substance capable of triggering an immune response. Anucleate Used to describe a cell without a nucleus. Apocrine Describes a sweat gland whose secretions flow into the pilary canal. They are only found in specific zones of the organism (armpit, pubic area, perineum, etc.). Apoptosis Or programmed cell death. Biological process during which the cells commit suicid, by fragmentation of their genetic matter. C Capillary vessel Very thin blood vessel organised in a network un every tissues. Gas, nutriment exchange and waste elimination in tissue take place at their level. Sun capital All the systems that defend the skin against the harmful effects of the sun. This degree of tolerance is acquired at birth, is not renewable and depends on an individual's phototype. Langerhans' Cell Epidermal dendritic cell involved in the immune response. Merkel Cell Sensory cell located on the baal layer of the epidermis, involved in the sense of touch. Ceramides Particular class of lipids naturally present in the skin and hair.

Intercellular cement Extra-cellular substance which ensures the cohesion of cells within a tissue. Connective tissue Tissue which has the role of supporting the other tissues (or organs of the body) and protecting, nourishing and holding them together. Corneocyte An anucleate, biologically dead cell, that characterises the distinctive end state of the keratincocytes. Corneodesmosomes Desmosomes that maintain cohesion between the corneocytes in the horny layer. Corneometer Device for measuring level of skin moisturisation. Malpighian layer Layer of the epidermis 5 to 6 cells deep that become flatter in the superficial part, often called the spinous layer or spinosum stratum. Meissner Corpuscle Sensory cell located in the dermis, on the boundary of the epidermis. These receptors are also involved in the sense of touch. Pacinian Corpuscle Sensory receptor highly sensitive to pressure and vibrations. They are located deep in the dermis and the hypodermis. Ruffinian Corpuscle Sensory receptor that are confined to the dermis and are stimulated by variations caused by tension and stretching.

Horny layer Differentiation layer Layer in the epidermis located between the mitotic layer and the horny layer. This is the layer in which keratinisation takes place. Cysteine Sulphur containing amino-acid, a constituent of proteins. Cytokine Branching prolongations of nerve cells, or cells of nervous origin. Densi-score Device for measuring skin creasing. Dermis Deep layer of the skin, covered by the epidermis and formed from connective tissue. Desmosome Connecting zone between two epithelial cells. Desquamation Elimination of superficial layers of the epidermis in the form of small flakes. Cellular differentiation Process by which an unspecialized cell becomes specialized into one of the many cells that make up the body, such as a heart, liver or muscle or skin cell. Cell division Usual method of cell multiplication in which a mother cell divides into two identical daughter cells, each containing a set of chromosomes identical to those of the mother cell. E Eccrine Describes a small sweat gland that leaves its secretions on the skin's surface. Eccrine sweat gland are ubiquitous.

Elasticity Property of certain bodies of returning to their original shape and volume when the force exerted on them ceases to act. Enzyme Protein which accelerates a biochemical reaction such as the chemical transformation of a given substance into another substance. Epidermis Superficial layer of the skin, covering the dermis and formed from epithelial tissue. Epithelium Tissue formed from one or more layers of cells which covers the body (epidermis), the internal cavities (mucosae) or which makes up the glands. Eumelanin G Lymph node Swelling in a lymph vessel in which the lymph is relieved of waste and infectious agents that it contains by lymphocytes and macrophages. Genotype All the genes carried by the chromosomes and which make up an individual's genetic inheritance. Sebaceous gland Skin appendage responsible for producing sebum. Sweat gland Skin appendage responsible for producing sweat. Glycoprotein Protein linked to one or more sugars. Birbeck granule H Hair follicle Invisible part of the hair buried 4 mm under the scalp and which is the place where the hair is produced. Henna Plant from the Middle-East and North Africa.

Dried and ground henna leaves produce a powder used to dye hair and nails. Hypodermis Deepest layer of the skin essentially made up of fatty cells, the adipocytes, and connective tissue. Hypothalamus Part of the central nervous system that controls sleep and sexual activity as well as hunger, thirst, body temperature control mechanisms and certain emotions. I In vitro (Latin words: "in glass") Used to describe any biological experiment carried out outside of the organism. As opposed to in vivo. In vivo (Latin words: "in the living") Used to describe any biological experiment carried out within the living organism. As opposed to in vitro. Infra-red (IR) Major part of the sun's rays, with a long wavelength, responsible for the heat effect. MRI K Keratin Sulphur rich fibrous protein, insoluble in water and very strong. It forms the essential part of hair fibre, the skin, nails, horns, hooves, feathers and wool. It is also present in the superficial cells of the epidermis. Keratinised About an epithelium having keratin as its main protein component.

Keratinocyte L Lipids Fatty chemical substances, found in all living organisms, playing a considerable role in cell structure and with an important energetic role as well. Lipometer Device for measuring the skin's lipid content. Lymph Organic yellow liquid essentially made up of water, lymphocytes and various organic substances (cholesterol) and minerals. Lymphocyte Cell found in the lymph nodes, thymus, bone marrow and spleen playing a role in the immune defence system. Coloured pigment giving colour to the hair and skin. Basement membrane Is described as being the interface between the cells and the extracellular matrix. Micrometer Unit of measurement equal to one millionth of a metre or a thousandth of a millimetre (formerly: micron). Melanocytes Cells of the epidermis or of hair follicles, responsible for the synthesis of melanin and transmitting it to the keratinocytes. Confocal Microscopy (C. M) Method of microscopy using Laser light beams, enabling the same object to be observed at successive depths. Scanning Electron Microscopy (S.E.M) Observation method using electron beams enabling surfaces to be examined and relief to be shown.

Possible enlargement from 10 to 100,000 times. Mitosis Usual method of cell multiplication in which a mother cell divides into two identical daughter cells, each containing a set of chromosomes identical to those of the mother cell. Programmed cell death Part of an organised body that carries out one or more defined functions. Organelle Any structure differentiated from the cell having the role of an organ, for example: mitochondria, Golgi bodies. Organites Any structure differentiated from the cell having the role of an organ, for example: mitochondria, Golgi bodies. Ostium P Squamous Used to describe a squamous or pavement epithelium has a superficial layer of cells, which are flat. It looks like a pavement. Peptide Molecule made up of a small number of amino acids. It is small protein. pH Abbreviation of "hydrogen potential".) Index expressing the activity (or concentration) of hydrogen ions in a solution. If the pH is less than 7, the solution is acidic. If it is equal to 7, it is neutral. If it is greater than 7, it is alkaline.

Phenotype All the apparent characteristics of an individual, which correspond both to the expressed part of the genotype and phenomena defined by the external environment. Phototype Classification of sensitivity to solar radiation based on skin, eye and hair colour. Physiology Science involving the study of an organ's functions and properties, and the tissue of a plant or animal. Piercing Inserting a jewel or decoration into the skin by perforation. Pigment Coloured matter in various plant or animal tissue and organs giving it a particular colour. Plexus Network of inter-woven nerves and blood vessels. Protï¿½ine Molecule made up of an association between 4 to several thousand amino acids and forming the essential component of cells (the word "protein" coming from the Greek prï¿½tos which means "first"). Serious neurological illness due to an intoxication from lead or lead salts. Scarring Symbolic ritual marking indicating ethnic membership or initiation. Sebum Greasy material produced by the sebaceous glands associated with the hair follicles and which naturally lubricates the hair. Stratified Used to describe an epithelium made up of several layers of cells (stratum = layer).

Stratum corneum T Tattooing Cultural tradition aiming at introducing pigments into the upper dermis so as to creates coloured designs. Tattoos are indelible. Thermoregulation Regulatory mechanism by which the internal temperature of the body of mammals and birds is maintained constant. Torquemeter U Ultraviolet (UV) Minority part of solar radiation, short wave but highly energetic. UV rays cause a lot of damage to the epidermis and to the dermis. V Lymphatic vessels Membranous duct punctuated with nodes in which the lymph circulates. They have a very similar structure to that of blood vessels. Visible radiation X Xeroderma Pigmentosum (XP) Rare genetic illness in which the enzymes that repair DNA are deficient. This dillness causes people to be highly sensitive to solar irradiation and are proned to develop cancers. Skin Pigmentation Disorders | definition of Skin Pigmentation Disorders by Medical dictionary Skin Pigmentation Disorders | definition of Skin Pigmentation Disorders by Medical dictionary Definition Skin pigmentation disorders are conditions that cause the skin to appear lighter or darker than normal, or blotchy and discolored. Description People of all races have skin pigmentation disorders.

Some disorders, like albinism (which affects one out of every 17,000 people) are rare. Others, such as age spots, are very common. Skin pigmentation disorders occur because the body produces either too much or too little melanin, a pigment that creates hair, skin, and eye color. Melanin protects the body by absorbing ultraviolet light. In hypopigmentation means the body does not produces enough melanin. Albinism, for example, is an inherited condition that causes a lack of pigment. So people with albinism typically have light skin, white or pale yellow hair, and light blue or gray eyes. Another condition called vitilgo, creates smooth, depigmented white spots on the skin. Vitilgo affects nearly 2% of the population, but it strikes people between 10 and 30 years old more often, and is more evident in people with darker skin. In hyperpigmentation , the body produces too much melanin, causing skin to become darker than usual. Lichen simplex chronicus is a skin disorder with severe itching that causes thick, dark patches of skin to develop.

Lamellar ichthyosis (fish scale disease) is an inherited disease that also is characterized by darkened, scaly, dry patches of skin. Hyperpigmentation also occurs in melasma, a dark mask-like discoloration that covers the cheeks and bridge of the nose. Melasma can occur during the end of pregnancy . People with the autoimmune disease (when immune cells, which attack invaders, become abnormally programed to kill self cells inside the body) systemic lupus also may develop a similar butterfly-shaped mask on their faces. In addition, many people have moles, freckles, age spots, and birthmarks , ranging from red or brown to bluish, black, covering various parts of their bodies. Causes and symptoms Scientists are still studying the reasons why skin pigmentation disorders occur. In some cases there are tangible causes, such as sun exposure, drug reactions or genetic inheritance. In other cases, it is not as clear. Albinism is an inherited recessive trait. Albinism has many different forms, but most people who have this condition have pale skin, hair, and eyes. Melanin also creates eye color, and serves as a filter that prevents too much light from entering the eye.

Since they lack melanin in their eyes, many people with albinism also have visual impairment . With little skin pigmentation, they also sunburn easily and are more prone to skin cancer . The hypopigmentation spots associated with vitilgo sometimes form where a person has been cut or injured. Research has shown that the light patches associated with vitilgo do not contain melanocytes, the type of skin cells that create melanin. Some scientists believe vitilgo may be caused by an autoimmune disorder. It also has been linked to other conditions such as hyperthyroidism (too much thyroid hormone) and Addison's Disease, which affects the adrenal gland. Hyperpigmentation can be caused by many factors, from too much sunbathing to drug reactions or poor nutrition . Wounds and scars also can develop darker patches of skin. A psychological syndrome gives people with lichen simplex chronicus to develop a compulsive need to scratch, which causes dark, leathery skin to form. This can lead to permanent scarring and infection if untreated. Scientists believe lamellar ichthyosis is caused by genetics. The mask caused by melasma may be related to pregnancy hormones, and usually disappears after a woman gives birth.

Birthmarks, moles , and aging spots usually are harmless. Some moles, however, can change in size, color, texture, or start bleeding, which could indicate possible skin cancer. Diagnosis Diagnostic tests vary for different types of skin pigmentation disorders. Physicians usually can diagnose albinism by looking carefully at a person's hair, skin, and eyes. They may order blood tests and eye exams as well. A visual exam also is enough to diagnose vitilgo. For most hyperpigmentation disorders, doctors can make a diagnosis by looking at a person's appearance. To detect conditions like lichen simplex chronicus or lamellar ichthyosis, or skin cancer, they may also do a biopsy to remove some of the affected skin for further study under a microscope. Some physicians also use a wood's lamp, or black light test, to diagnose skin conditions. Affected areas would absorb the ultraviolet light and stand out with flourescent colors in the darkened room. Key terms Albinism — An inherited condition that causes a lack of pigment.

People with albinism typically have light skin, white or pale yellow hair and light blue or gray eyes Hyperpigmentation — A skin condition that occurs when the body has too much melanin, or pigment. Hypopigmentation — A skin condition that occurs when the body has too little melanin, or pigment. Lamellar ichthyosis — Also called fish scale disease, this inherited condition is characterized by darkened, scaly, dry patches of skin. Lichen simplex chronicus — A skin disorder with severe itching that causes thick, dark patches of skin to develop. Melanin — A pigment that creates hair, skin and eye color. Melanin also protects the body by absorbing ultraviolet light. Melanocytes — The type of skin cells that create melanin. Melasma — A dark mask-like discoloration that covers the cheeks and bridge of the nose. Also called "the mask of pregnancy." Vitilgo — A skin disorder that creates smooth, depigmented white spots on the skin. Treatment For albinism, healthcare providers advise people to cover up, use sunscreen and avoid excess sunlight to prevent skin cancer. People with albinism also must wear protective sunglasses and, in some cases, prescription corrective lenses.

Surgery may be necessary to correct visual impairments. To treat vitilgo, physicians may prescribe a combination of photo-sensitive medications like trimethylpsoralen and ultraviolet light therapy to darken the spots. If the person has depigmented patches covering more than 50% of the body, doctors also may be able to use skin bleaching agents like monobenzone to give the skin a lighter, more uniform appearance. Other options include cosmetic concealers and skin grafting . Skin-lightening creams are available for hyper-pigmentation disorders. Doctors also advise staying out of the sun. Counseling with a dietitian may help in cases caused by poor nutrition. For lichen simplex chronicus, doctors could prescribe antihistamines and topical steroid creams to stop the itching. If a mole or birthmark appears suspicious, physicians often will surgically remove it to prevent skin cancer. Prognosis Pigmentation | Article about pigmentation by The Free Dictionary Pigmentation | Article about pigmentation by The Free Dictionary Also found in: Dictionary , Thesaurus , Medical , Wikipedia . pigmentation, name for the coloring matter found in certain plant and animal cells and for the color produced thereby. Pigmentation occurs in nearly all living organisms.

Almost all plants synthesize their own pigments; animals either derive pigments from plant foods or synthesize them themselves. In plants the major pigments are the carotenes (reddish orange to yellow), the anthocyanins (red, blue, and violet), and the chlorophylls (green). The red and yellow colors of autumn foliage are due to the exposure of the anthocyanins after the green chlorophyll pigments, which usually mask them, have decomposed and faded. The major animal pigments are the hemes (red) of blood hemoglobin, the carotenes, the melanins (black and brown), and guanine (white and iridescent). The latter three produce the surface coloration of most animals. Pigments not only provide external coloration but also function in some important physiological processes. In the retina of the eye the pigment cells (rods and cones) adjust or regulate the entering light (see vision vision, physiological sense of sight by which the form, color, size, movements, and distance of objects are perceived. Vision in Humans The human eye functions somewhat like a camera; that is, it receives and focuses light upon a photosensitive receiver, the retina. .....

Click the link for more information. ). Among its other functions, carotene operates in the synthesis of vitamins and of chlorophyll. Chlorophyll is essential for plant photosynthesis photosynthesis , process in which green plants, algae, and cyanobacteria utilize the energy of sunlight to manufacture carbohydrates from carbon dioxide and water in the presence of chlorophyll. Some of the plants that lack chlorophyll, e.g. ..... Click the link for more information. . Hemoglobin in the blood carries oxygen for respiration. Chlorophyll and hemoglobin are structurally quite similar, both belonging to the pyrrole group of pigments. Human Pigmentation In humans the degree of darkness of the skin, hair, and iris of the eye depends primarily on the amount of melanin present. The presence of hemoglobin and carotene in the blood blood, fluid pumped by the heart that circulates throughout the body via the arteries, veins, and capillaries (see circulatory system; heart). An adult male of average size normally has about 6 quarts (5.6 liters) of blood. ..... Click the link for more information. contributes to skin color.

Moles and freckles are caused by high local concentrations of melanin; albinism by a lack of melanin; and some birthmarks, e.g., "strawberry marks," by an unusual local proliferation of blood vessels (and hence of hemoglobin) near the skin surface. Tanning of human skin results from an increase of melanin production under the stimulation of ultraviolet light. Pigment and Refraction in Coloration The coloration of an organism may be caused by deposits of organic pigments in the tissues (as in human skin or in plant leaves), by optical effects of the refraction of light rays (as in mollusk shells and in some butterfly wings and bird feathers), or by a combination of both (see color color, effect produced on the eye and its associated nerves by light waves of different wavelength or frequency. Light transmitted from an object to the eye stimulates the different color cones of the retina, thus making possible perception of various colors in the object. ..... Click the link for more information. ).

The different modes are illustrated in the baboon and the mandrill: the predominantly brown coloring is due to melanin, but the red and blue markings are also caused by melanin, in the latter case by the refraction of light due to specific spatial arrangements of the pigment granules in the skin areas involved. Pigmentation Adaptation in Animals The pigmentation of many animals is adapted to their environment and aids in their survival (see mimicry mimicry, in biology, the advantageous resemblance of one species to another, often unrelated, species or to a feature of its own environment. (When the latter results from pigmentation it is classed as protective coloration. ..... Click the link for more information. ; protective coloration protective coloration, coloration or color pattern of an animal that affords it protection from observation either by its predators or by its prey. The most widespread form of protective coloration is called cryptic resemblance, in which various effects that supplement the ..... Click the link for more information. ). In some animals the pigment is changeable; the flounder and the squid, for example, are capable of adapting themselves to the color of their background and thus often of escaping detection by their enemies.

The exact mechanism of such changeability is not clearly understood, but in most cases it is due primarily to visual stimulation. In the squid the chromatophores (containing melanin granules) are controlled by muscles and can expand from an almost invisible pinpoint to 60 times their original size, giving the whole animal a dark appearance. Pigmentation changes are also at least partially controlled by hormones—as, in part, is pigmentation synthesis itself. Pigmentation A property of biological materials that imparts coloration. Hence, pigmentation determines the quantity and quality of reflected visible light. The characteristics of light returning from living matter are a function of its chemical and physical properties and, therefore, are not only due to pigments proper but can be of structural origin (for example, due to reflection, scattering, or interference) as well. Pigments are essential constituents of the living world. Their contribution to the evolution and maintenance of life, and its manifold expressions, is most evident in the role of chlorophylls and the associated carotenoids of certain bacteria and most plants. These pigments harvest solar light energy for utilization in the photosynthesis of organic material from inorganic precursors.

See Chlorophyll , Photosynthesis The outermost structures on the animal skin are pigmented for many reasons, for example, to reduce the animal's visibility against a colored background or to provide optical signals to the other sex or to other species. Conspicuously pigmented flowers attract pollinators, and colored fruits are easily found by animals, which eat them and then disperse the undigested seeds. The role of pigments in communication depends on the ability of organisms to discriminate between different regions of the solar spectrum. In animals with eyes, this is accomplished by differently colored visual pigments contained in specialized receptor cells. Microorganisms, fungi, and plants also have special pigment systems that permit these organisms to move or grow toward, or away from, light (positive and negative phototaxis and phototropism, respectively). See Plant movements Since most organisms are totally dependent on light—at least indirectly—elaborate pigment systems have evolved which tune metabolic and activity patterns to the daily pattern of light and dark, and to the changes in the relative lengths of day and night in the course of a year.

The phytochrome of plants and the pigments of the eye or of extraretinal photoreceptor organs of many vertebrates and invertebrates are typical representatives of pigments that correlate biological activity with light-dark cycles (photoperiodism). See Color vision , Photoperiodism , Photoreception In the examples listed above, pigments mediate, in various ways, the beneficial actions of light. Absorbed solar light energy may, however, also have detrimental effects by causing undesirable or even destructive reactions. Pigmentations can provide a light-absorbing shield that protects the tissue below from such potentially damaging radiation of the Sun. See Skin Pigmentation the coloration of tissues and organs as a result of the formation and deposition of pigments. The pigmentation of skin, hair, and the iris, which depends on the quantity and distribution of the pigment melanin, is one of the main racial features that are considered in anthropology. Melanin is found in tissues in the form of granules or a solution in the cellular protoplasm. Skin color results from the presence of melanin in the epidermis and the translucence of capillaries in the derma.

Melanin is formed by melanocytes, which are specialized cells in the basal layer of the epidermis. In light-skinned peoples the basal layer contains only a few melanin granules, while in dark-skinned peoples the layer is packed with granules. Skin color is not uniform throughout the body. The extensor surfaces of the extremities are darker than the flexor surfaces, and the back is more pigmented than the chest or abdomen. Coloration is most intense around the nipples. Even in dark-skinned peoples, the palms and soles are light. The lips of light-skinned peoples are covered by a nonpigmented mucous membrane, and the red color of such lips is due to the translucence of labial capillaries. On the other hand, melanin in the mucous membrane imparts a bluish color to the lips of dark-skinned peoples. Exposure to the sun darkens the skin because solar rays intensify the formation of melanin, which is capable of absorbing the ultraviolet light that harms tissues. In this manner, dark skin protects an organism against sunlight.

Skin color varies from pinkish, in light-skinned peoples of Europe, to chocolate, mostly in peoples that inhabit the tropics, for example, African Negroes, Papuans, Melanesians, and Australians. It is one of the most important inherited racial characteristics. Hair color is also determined by the content of melanin, chiefly in the cortex of the hair. Melanin granules are formed in melanocytes, which are present in the epithelium of the hair follicle. Dark hair is rich in pigment granules, which can penetrate into the medullary column, or pith, of the hair; light hair has fewer and smaller granules. Melanin in solution imparts a reddish tint to hair. Hair color changes with age, light hair becoming darker. Graying is caused by the cessation of melanin biosynthesis. People with light or reddish hair are predominantly found only in northwestern Europe; elsewhere, dark hair is prevalent, but the intensity and shade vary even among dark-pigmented populations. The color of the iris depends on the quantity of melanin and the depth at which the melanin is deposited. The pigment is found in the pigmented layer and the posterior limiting layer of the iris.

If the anterior layers are nonpigmented, the melanin that shows through them imparts a dark or light blue color to the iris. If the pigment is also present in the anterior layers (the simple squamous epithelium and the stroma), the iris appears yellow or brown. An uneven distribution of pigment in the anterior layers produces green eyes, gray eyes, and eyes that appear to contain a mixture of yellow, brown, and light blue. The presence of large quantities of pigment in the anterior layers accounts for eyes that are black or brown. In some populations, women’s eyes are somewhat darker than men’s. Dark eyes lighten with age, while light eyes darken. Eye color more or less corresponds to hair color, although in moderately pigmented populations light eyes are found more often than light hair. The absence of normal pigmentation in the skin, hair, and iris, a condition called albinism, is due to a hereditary disturbance in melanin biosynthesis.

REFERENCES Albinism | definition of albinism by Medical dictionary Albinism | definition of albinism by Medical dictionary Related to albinism: Ocular Albinism Albinism Definition Albinism is an inherited condition present at birth, characterized by a lack of pigment that normally gives color to the skin, hair, and eyes. Many types of albinism exist, all of which involve lack of pigment in varying degrees. The condition, which is found in all races, may be accompanied by eye problems and may lead to skin cancer later in life. Description Albinism is a rare disorder found in fewer than five people per 100,000 in the United States and Europe. Other parts of the world have a much higher rate; for example, albinism is found in about 20 out of every 100,000 people in southern Nigeria. There are 10 types of the most common form of the condition, known as "oculocutaneous albinism," which affects the eyes, hair, and skin. In its most severe form, hair and skin remain pure white throughout life.

People with a less severe form are born with white hair and skin, which turn slightly darker as they age. Everyone with oculocutaneous albinism experiences abnormal flickering eye movements ( nystagmus ) and sensitivity to bright light. There may be other eye problems as well, including poor vision and crossed or "lazy" eyes (strabismus). The second most common type of the condition is known as "ocular" albinism, in which only the eyes lack color; skin and hair are normal. There are five forms of ocular albinism; some types cause more problems-especially eye problems-than others. Causes and symptoms Every cell in the body contains a matched pair of genes, one inherited from each parent. These genes act as a sort of "blueprint" that guides the development of a fetus. Albinism is an inherited problem caused by a flaw in one or more of the genes that are responsible for directing the eyes and skin to make melanin (pigment). As a result, little or no pigment is made, and the child's skin, eyes and hair may be colorless.

In most types of albinism, a recessive trait, the child inherits flawed genes for making melanin from both parents. Because the task of making melanin is complex, there are many different types of albinism, involving a number of different genes. It's also possible to inherit one normal gene and one albinism gene. In this case, the one normal gene provides enough information in its cellular blueprint to make some pigment, and the child will have normal skin and eye color. They "carry" one gene for albinism. About one in 70 people are albinism carriers, with one flawed gene but no symptoms; they have a 50% chance of passing the albinism gene to their child. However, if both parents are carriers with one flawed gene each, they have a 1 in 4 chance of passing on both copies of the flawed gene to the child, who will have albinism. (There is also a type of ocular albinism that is carried on the X chromosome and occurs almost exclusively in males because they have only one X chromosome and, therefore, no other gene for the trait to override the flawed one.) Symptoms of albinism can involve the skin, hair, and eyes.

The skin, because it contains little pigment, appears very light, as does the hair. Although people with albinism may experience a variety of eye problems, one of the myths about albinism is that it causes people to have pink or red eyes. In fact, people with albinism can have irises varying from light gray or blue to brown. (The iris is the colored portion of the eye that controls the size of the pupil, the opening that lets light into the eye.) If people with albinism seem to have reddish eyes, it's because light is being reflected from the back of the eye (retina) in much the same way as happens when people are photographed with an electronic flash. People with albinism may have one or more of the following eye problems: They may be very far-sighted or near-sighted, and may have other defects in the curvature of the lens of the eye ( astigmatism ) that cause images to appear unfocused. They may have a constant, involuntary movement of the eyeball called nystagmus. They may have problems in coordinating the eyes in fixing and tracking objects (strabismus), which may lead to an appearance of having "crossed eyes" at times.

Strabismus may cause some problems with depth perception, especially at close distances. They may be very sensitive to light (photophobia) because their irises allow "stray" light to enter their eyes. It's a common misconception that people with albinism shouldn't go out on sunny days, but wearing sunglasses can make it possible to go outside quite comfortably. In addition to the characteristically light skin and eye problems, people with a rare form of albinism called Hermansky-Pudlak Syndrome (HPS) also have a greater tendency to have bleeding disorders, inflammation of the large bowel (colitis), lung (pulmonary) disease, and kidney (renal) problems. Diagnosis It's not always easy to diagnose the exact type of albinism a person has; there are two tests available that can identify only two types of the condition. Recently, a blood test has been developed that can identify carriers of the gene for some types of albinism; a similar test during amniocentesis can diagnose some types of albinism in an unborn child. A chorionic villus sampling test during the fifth week of pregnancy may also reveal some types of albinism.

The specific type of albinism a person has can be determined by taking a good family history and examining the patient and several close relatives. The "hairbulb pigmentation test" is used to identify carriers by incubating a piece of the person's hair in a solution of tyrosine, a substance in food which the body uses to make melanin. If the hair turns dark, it means the hair is making melanin (a "positive" test); light hair means there is no melanin. This test is the source of the names of two types of albinism: "ty-pos" and "ty-neg." The tyrosinase test is more precise than the hairbulb pigmentation test. It measures the rate at which hair converts tyrosine into another chemical (DOPA), which is then made into pigment. The hair converts tyrosine with the help of a substance called "tyrosinase." In some types of albinism, tyrosinase doesn't do its job, and melanin production breaks down. Treatment There is no treatment that can replace the lack of melanin that causes the symptoms of albinism.

Doctors can only treat, not cure, the eye problems that often accompany the lack of skin color. Glasses are usually needed and can be tinted to ease pain from too much sunlight. There is no cure for involuntary eye movements (nystagmus), and treatments for focusing problems (surgery or contact lenses) are not effective in all cases. Key terms Amino acids — Natural substances that are the building blocks of protein. The body breaks down the protein in food into amino acids, and then uses these amino acids to create other proteins. The body also changes amino acids into melanin pigment. Astigmatism — An eye condition in which the lens doesn't focus light evenly on the retina, leading to problems with visual sharpness. Carrier — A person with one normal gene and one faulty gene, who can pass on a condition to others without actually having symptoms. DNA — The abbreviation for "deoxyribonucleic acid," the primary carrier of genetic information found in the chromosomes of almost all organisms. The entwined double structure allows the chromosomes to be copied exactly during cell division.

DOPA — The common name for a natural chemical (3, 4-dihydroxyphenylalanine) made by the body during the process of making melanin. Enzyme — A protein that helps the body convert one chemical substance to another. Gene — The basic unit of genetic material carried in a particular place on a chromosome. Genes are passed on from parents to child when the sperm and egg unite during conception. Hairbulb — The root of a strand of hair from which the color develops. Hermansky-Pudlak Syndrome (HPS) — A rare type of albinism characterized by a problem with blood clotting and a buildup of waxy material in lungs and intestines. Melanin — Pigment made in the hair, skin and eyes. Nystagmus — An involuntary back-and-forth movement of the eyes that is often found in albinism. Strabismus — Crossed or "lazy" eyes, often found in albinism. Tyrosinase — An enzyme in a pigment cell which helps change tyrosine to DOPA during the process of making melanin.

Tyrosine — A protein building block found in a wide variety of foods that is used by the body to make melanin. Crossed eyes (strabismus) can be treated during infancy, using eye patches, surgery or medicine injections. Treatment may improve the appearance of the eye, but it can do nothing to cure the underlying condition. Patients with albinism should avoid excessive exposure to the sun, especially between 10 a.m. and 2 p.m. If exposure can't be avoided, they should use UVA-UVB sunblocks with an SPF of at least 20. Taking beta- carotene may help provide some skin color, although it doesn't protect against sun exposure. Prognosis In the United States, people with this condition can expect to have a normal lifespan. People with albinism may experience some social problems because of a lack of understanding on the part of others. When a member of a normally dark-skinned ethnic group has albinism, he or she may face some very complex social challenges. One of the greatest health hazards for people with albinism is excessive exposure to sun without protection, which could lead to skin cancer.

Wearing opaque clothes and sunscreen rated SPF 20, people with albinism can safely work and play outdoors safely even during the summer. Prevention American Foundation for the Blind. 15 W. 16th St., New York, NY 10011. (800) AFB-LIND. Hermansky-Pudlak Syndrome Network, Inc. One South Road, Oyster Bay, NY 11771-1905. (800) 789-9477. 〈appell@theonramp.net〉. National Organization for Albinism and Hypopigmentation (NOAH). 1530 Locust St., #29, Philadelphia, PA 19102-4415. (800) 473-2310.

albinism [al´bĭ-nizm] a hereditary disorder, usually transmitted as an autosomal recessive trait, in which there is partial or total absence of pigment in the skin, hair, and eyes (oculocutaneous albinism) or in the eyes alone (ocular albinism), caused by defective or absent function of the enzyme tyrosinase. It is imperative that individuals affected with albinism be taught how to protect themselves from the harmful effects of the sun. al·bi·nism (al'bi-nizm), A group of inherited (usually autosomal recessive) disorders with deficiency or absence of pigment in the skin, hair, and eyes, or eyes only, resulting from an abnormality in melanin production. See: ocular albinism , piebaldism .

[albino + ism] albinism /al·bi·nism/ (al´bĭ-nizm) congenital absence, either total or partial, of normal pigmentation in the body (hair, skin, eyes) due to a defect in melanin synthesis.albinot´ic ocular albinism that in which skin and hair pigmentation is virtually or wholly normal, with ocular abnormalities varying by type. oculocutaneous albinism (OCA) a human albinism occurring in ten types, all having in common decreased melanotic pigmentation of the hair, skin, and eyes, hypoplastic foveas, photophobia, nystagmus, and decreased visual acuity. albinism (ăl′bə-nĭz′əm) n. 1. Any of several inherited conditions characterized by the reduction or absence of the pigment melanin in a person or animal, resulting in lack of pigmentation in the eyes, skin, and hair. Humans with albinism usually have vision problems. 2. Lack of chlorophyll in a plant or plant part, resulting in a pale color. al′bi·nis′tic adj.

albinism [al′biniz′əm] a rare inherited disorder characterized by a lack of melanin in the skin. Total albinos have pale skin that does not tan, white hair, pink eyes, nystagmus, astigmatism, and photophobia. Albinos are prone to severe sunburn, actinic dermatitis, and skin cancer. Compare piebald, vitiligo . White hair and pale skin in albinism albinism A group of hereditary and congenital, often AR diseases that share a metabolic defect in the production of mature melanin, which translates clinically into hypopigmentation of skin, hair, and eyes–iris See Oculocutaneous albinism type I, Oculocutaneous albinism type II, Yellow albinism.

Albinism, major groups Generalized (oculocutaneous) albinism All 6 subtypes are AR; the most common, type IA is due to tyrosinase deficiency, which may be due to a missense mutation; GA also occurs in Chediak-Higashi, Hermansky-Pudlak, & Cross syndromes Partial albinism al·bi·nism (al'bi-nizm) A group of inherited (usually autosomal recessive) disorders with deficiency or absence of pigment in the skin, hair, and eyes, or eyes only, due to an abnormality in production of melanin. See: ocular albinism , piebaldism albinism Congenital absence of the normal body colouring pigment MELANIN . This is formed from tyrosine by the action of an enzyme tyrosinase present in cells called melanocytes. There are two kinds of albinism, tyrosinase positive and tyrosinase negative, due to mutations in different GENES that are not ALLELES . Albinism is an AUTOSOMAL RECESSIVE inheritance.

Because the two mutations are on unrelated genes, people HETEROZYGOUS for both of the abnormal genes have normal colouring. For the same reason, two albino parents do not necessarily have albino children. Tyrosinase negative people are completely free of pigment, have pure white hair, pink-white skin and blue eyes and usually have visual problems. Tyrosinase positive people are less severely affected. Albinos often have defective eyesight from pigment deficiency in the eyes, and usually suffer from NYSTAGMUS . Fig. 20 Albinism . Blockage in tyrosine metabolism. albinism an inherited condition found in many organisms, whose chief feature is a lack of MELANIN pigment in structures that are normally coloured. In humans the syndrome of albinism comprises: pinkish skin in which the pigment-containing cells (MELANOPHORES) are present but contain little or no melanin. The pinkish coloration comes from the underlying blood vessels. eyes with a deep red pupil and pink iris, both due to a lack of normal pigmentation and heavy vascularization. photophobia (fear of light) brought on by excess light entering the eye and reflecting onto the retina.

Albinos usually wear dark glasses. pale yellow hair. Albinism is an INBORN ERROR OF METABOLISM produced by a blockage in tyrosine metabolism due to the absence of a functional tyrosinase enzyme. The condition is controlled by a single RECESSIVE GENE on an AUTOSOME . Approximately 1 in 20 000 of the population are albinos. See Fig. 20 . albinism congenital inherited absence of pigmentation in skin, hair and eyes due to melanocyte dysfunction or deficiency albinism, Glossary Glossary WXYZ Aestivate - To remain inactive during a prolonged period of high temperatures or drought, usually while hidden. (also estivate) Albino - An animal with a congenital absence of pigment in the skin and eyes (which are typically pink.) Allopatric - Describes two or more taxa which have geographic ranges that are completely separated. (Compare with sympatric and parapatric.) Amelanistic - Lacking melanin, or dark pigment, but not all pigment, as with an albino.

Amplexus - The sexual embrace of a male amphibian (when a male frog or salamander clasps the female from behind or above with his forelimbs either behind her forelimbs - axillary amplexus - or at her rear legs or waist - inguinal amplexus.) Anal Spur - Vestigial hind limbs on each side of the vent of a boid snake appearing as a pointed spur. Anerythristic - Lacking the red (or orange) coloration (erythrin) which normally occurs. (EG. a snake that is normally black, red, and white, that is black and white only.) Anterior - Toward the front or head end. Antibiosis - an antagonistic association between two organisms in which one is adversely affected. Anuran - A frog or toad. Aposematic - (of coloration or markings) serving to warn or repel predators. Colored or constructed in a way that indicates special capabilities for defense. Aquatic - Frequenting, living, or growing in water. Arboreal - Living in trees or shrubs. Arenicolous - Inhabiting sand. Attenuated - Thin or slender.

Autotomy - The spontaneous casting off of the tail when under attack. Lizards and Salamanders both have the ability to release the tail when it has been grasped, and sometimes when it hasn't. The tail continues wiggling which distracts the predator allowing the lizard or salamander to escape. The tail later regenerates or grows back, although not usually to the same length. Axillary - Relating to the armpits. Barbel - A nipple-like projection. A slender tactile fleshy growth. Batrachology - the study of amphibians. Batesian Mimicry - a form of mimicry typified by a situation where a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator. ( Wickipedia ) Behaviourism - The scientific study of the trained behavioral responses of animals in a laboratory context. (See ethology) Biotic - of, relating to, or resulting from living things, especially in their ecological relation.

Boss - A raised rounded area (often inbetween the eyes of a toad.) CA - Abbreviation for "California" (This is for those Europeans who have emailed me complaining they didn't understand what it means.) Carapace - The upper part of the shell of a turtle. Caudal - Pertaining to the tail. Caudals - The scales beneath the tail (often in two rows on some snakes.) (subcaudals) Chemoreceptor (Chemosensor) - a sensory receptor that detects certain chemical stimuli in the environment. Clinal Variation - A geographic character gradient - (differences in color or pattern in one species at southern point in range from northern). Cline - A gradual change in a variable characteristic. Cloaca - The cavity at the end of the digestive tract which serves for excretion and reproduction (See vent.) Clutch - A group of eggs fertilized at the same time, and typically laid in a single session and incubated together. Cold-blooded - Without a constant body temperature regulated by the animal's metabolism. A cold-blooded animal adjusts its body temperature by exposing it to warmer or cooler situations, such as basking in the sun, or going underground.

Commensalism - an association between two organisms in which one benefits and the other derives neither benefit nor harm. Costal Folds - The vertical folds of skin on the sides of the body of a salamander between the costal grooves. Costal Grooves - The vertical grooves in the skin on the sides of the body of a salamander between the costal folds. Cranial Crest - The raised ridges on the head of a toad, either between or behind the eyes. Crepuscular - Active during twilight; active at dawn and dusk. Crypsis -The ability to avoid observation or detection. Camouflaging behavior. Cycloid Scales - Smooth rounded scales. Dimorphic - Different in color or structure (males and females of a species are sexually dimorphic when they differ in color or structure.) Dimorphism - Difference in color or structure between members of the same species. (Sexual dimorphism is differences between males and females of the species.) Diurnal - Active during daytime. Dorsal - Relating to the upper side or back. Dorsolateral - Involving the upper surfaces of the sides below the back.

Dorsolateral Fold - The glandular ridge running lengthwise on the sides or back of a frog. Dorsum - The upper part of the body or back. Ecology - the branch of biology that deals with the relations of organisms to one another and to their physical surroundings, Ecosystem - A biological community of interacting organisms and their physical environment; the interaction among plants and animals in a given environment. Endemic - Native or confined to a certain region or country. Estivate - To remain inactive during a prolonged period of hight temperatures or drought, usually while hidden. (Aestivate) Ethology - The scientific study of the behavior of animals under natural conditions. (See behaviourism) Exotic - Not native to a region; originating elsewhere; Alien Femoral Pore- Small openings on the undersides of the thighs of some families of male (and sometimes female) lizards that are a part of glands that release pheromones to attract mates or mark territory. Fieldherping - The activity of searching for wild herps.

("Wild" meaning living in a natural environment (the field); not captive or domesticated.) Motives for fieldherping include, but are not limited to, observation, lifelisting, photography, and collecting herps. (Many herpers use the term "Herping" to mean "Fieldherping," but Herping has now become a catch-all term to incude any herp-related activity.) Form - A species, subspecies, or distinct identifiable population. Fossorial - Adapted for burrowing. Genus - A group of closely related species having common characteristics distinct from those of other such groupings. Gills - The paired respiratory organ of salamanders by which oxygen is extracted from water. Granules - Very small, flat scales. Gravid - Bearing eggs or young. Gular - Pertaining to the throat. Habitat - The natural home or environment of an organism. Hatchling - A recently hatched animal; an animal that has recently emerged from an egg. Hemipenis - Either of the paired copulatory organs of male snakes and lizards.

(plural - Hemipenes) Herp - A reptile, amphibian, or amphisbaenian (ie frogs, toads, salamanders, caecilians, turtles, lizards, snakes, crocodiles, alligators, and worm lizards.) (The term is short for herptile, which is a composite of herpetology and reptile.) Herpetoculture - Keeping live herps in captivity. Herpetofauna - The reptiles and amphibians of a particular region, habitat, or geological period. Herpetology - The study of amphibians and/or reptiles. Herper - A person who is involved with herps. Herpes - A viral disease that has nothing to do with herps! (A common misspelling of the plural form of the word herp.) Herping - Any activity involving captive or wild herps, including, but not limited to, fieldherping, herp photography, going to reptile shows and pet stores, and researching herps online or in a library. (The word once referred to fieldherping, but it has been appropriated by herpers who are not involved in fieldherping.) Herptile - a reptile or amphibian.

Hibernaculum - A place where an animal seeks refuge from cold temperatures in order to hibernate, or overwinter. Hydric - very wet. Horizontal Pupil - An elliptical pupil with its long axis horizontal. Hybrid - The offspring of the mating of two distinct species. Hypomelanistic - lacking melanin or dark pigmentation. In Situ - in its original place, as it was found Indigenous - Originating or occurring naturally in a particular place; native. Inguinal - Of, relating to, or located in the Groin. Insectivorous - feeding on worms, insects, and other invertebrates. Intergrade - An animal that shares the characteristics of two closely related subspecies of the same species (but is not a specific subspecies as it does not show the exact characteristics of any subspecies.) Animals within intergrade zones are usually highly variable in appearance. They can look like any one of the subspecies that share the zone or have characteristics of more than one subspecies. Interspace - the patch of color between markings (bands or blotches) on lizards and snakes. Juvenile - A young animal not yet sexually mature, often showing colors and proportions that differ from adults of the species.

Keel - A ridge that runs lengthwise along the center of a scale. Labial - Relating to the lips. Larva (pl. Larvae) - An immature form of a frog or salamander that must undergo metamorphosis to assume adult characteristics. Lateral - Referring to the side. Lateral Stripe - A stripe running lengthwise along the body. Lentic - inhabiting or situated in still fresh water. Lotic - inhabiting or situated in rapidly moving fresh water. Melanin - dark (black or brown) pigment. Melanistic - A condition of dark coloration of the skin due to a high concentration of the pigment melanin. (An unusual amount of black pigmentation.) Melanophore - A pigment cell containing melanin. Mental Gland - A gland on the chins of some male salamanders, the secretions from which are used to stimulate a sexual response in females of the species. Mesic - of, pertaining to or adapted to a habitat or environment containing a moderate amount of moisture. Metamorph - A recently metamorphosed frog, toad, or salamander.

Metamorphose - To undergo metamorphosis from a larval state to an adult state (frogs and toads and certain salamanders.) Microhabitat - A small part of an animal's habitat. (For example: the area under a rock which the animal utilizes occasionally, as opposed to the surrounding habitat where the rock is found.) Monotypic - A genus with only one species; the only representative of a group. Morphology - the study of the forms of living organisms, and with relationships between their structures. The branch of biology that deals with the form of living organisms, and with relationships between their structures. Morphotype - A physically distinct population with a geographical range that does not conform to taxonomy based on molecular evidence (includes many accepted subspecies.) Mottled - Irregularly marked with blotches and spots. Mullerian Mimicry - when two harmful species that are not closely related and share common predators have evolved to mimic each others warning signals. Nares - Nostrils Nasolabial Groove - In Plethodontid salamanders - a fine groove that extends from the nostril to the edge of the lip containing chemoreceptors.

Native - Of indigenous origin or growth; a local inhabitant; associated with a country or region. Neonate - A newborn. Neotenic - Remaining in the aquatic larval condition beyond the usual time of metamorphosis. Neoteny - Retention of juvenile characteristics in the adults of a species; Retaining larval features throughout adult life. Neurotoxic - Components of snake venom that damage the nervous system and often causing paralysis. Nocturnal - Active at night. Non-Venomous - Not capable of producing a venom that is dangerous to humans. (Many snakes long considered nonvenomous have been found to produce a venom that is harmful to their prey, usually through small rear fangs that very rarey can inject this venom into humans.) Nuchal - Referring to the back of the neck. Nuptial Pad - A rough patch of dark skin on the fingers of some male amphibians during the breeding season to help the male hold on to a female during amplexus. Ocelli - Round, eye-like spots. Ocular Scale - The enlarged scale covering the vestigial eyes on a blind snake (threadsnake.) Ophidian - Referring to snakes.

Ophiophagous - Feeding on snakes. Oviporous - Producing eggs that hatch after they are laid, with little or no other embryonic development within the mother. Ovoviparity - A mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch.. Paedomorph - An adult organism that has retained the juvenile characteristics. Pedogenesis - Neoteny. Papillae - Small, nipple-like protuberances. Parapatric - Describes two or more taxa which have geographic ranges that meet but do not overlap substantially. (Compare with allopatric and sympatric.) Parasite- an organism that lives on an organism (its host) and benefits by deriving nutrients at the expense of the host. Parotoid Glands - (Parotid Glands) Wartlike poison glands that occur on the backs, the necks, the shoulders, and the tails of some toads and salamanders. Parthenogenesis - Reproduction without fertilization by a male. Pectoral - Relating to the chest. Phylogeography - The study of the historical processes that may be responsible for the contemporary geographic distributions of individuals.

This is accomplished by considering the geographic distribution of individuals in light of the paatterns associated with a gene genealogy. ( Wickipedia ) Plastron - The underside of the shell of a turtle. Plethodon - Lung-less salamanders of the genus Plethodon. Polymorphic - Occurring in several different forms. (A species is polymorphic when it contains a number of different color morphs with respect to ground color, blotching, stripes, flecking, within and between populations, including clutches.) Posterior - Referring to the rear part of the body. Polymorphism - Having more than one form or appearance. Postanal Scale - A scale in back of the vent. Postocular - Behind the eye. Postocular Stripe - A stripe behind the eye. Preanal scale - A scale in front of the vent. Prehensile - A tail that can grasp or wrap around something. Preocular - In front of the eyes. Race - Subspecies. Reticulum - A netlike formation or structure; a fine network. Riparian - Wetlands adjacent to rivers and streams. Sacran Hump (Sacral Prominence) - The rounded raised part of the lower back in anurans.

Saxicolous - Living or growing among rocks (saxatile). Semiaquatic - Moving in and out of water, but not containing gills to extract oxygen from water. Sexual Dimorphism - differences between males and females of the species. Scansorial - Adapted for climbing. Habitually climbing. Scute - One of the horny plates covering the shell of a turtle. A large scale. Subadult - An animal that is not fully adult. Subcaudals - The scales beneath the tail (often in two rows on some snakes.) (caudals) Subocular - Beneath the eye Subspecies - A subdivision of a species which ranks below species, usually a fairly permanent geographically isolated race. SVL - (Snout-to-Vent Length) Length measured from the snout to the vent. Symbiosis - a mutually beneficial interaction between two different organisms living in physical association. Sympatric - Describes two or more taxa which have geographic ranges that overlap substantially. (Compare with allopatric and parapatric.) Synonym - In taxonomy, a synonym is a different name for the same species or type of organism.

Synonymize - To demonsrate that a taxonomic name is a synonym, which is one of two or more scientific names used to designate the same taxonomic group. (IE. to show that there is more than one scientific name for an animal, recommending that only one specific name be used in the future.) Syntopic - Different species found sharing the same habitat within the same geographic range. Talus - Rocks piled up at the base of a slope or cliff. Taxon (TAXA pl.) - A specific taxonomic category - e.g., a specific species or genus. Tibia - The leg of frog or toad from the heel to the knee. Total Length - Length measured from snout to the end of the tail. Troglodyte - A cave dweller. Tubercle - A small bump or knob on the body, which is smaller than a wart. Tympanum - Eardrum (enlarged on certain frogs.) Type Specimen - "The specific specimen on which the scientist who first names a new taxon bases the original description.

One individual is designated as the holotype, the name bearer, in order to permanently attach the name to a single taxon in the event that later research reveals that the type series was composed of more than one species." Venomous - capable of injecting venom (by means of their bite, regarding snakes and lizards.) Vent - The cloacal opening which serves for excretion and reproduction. Venter - The underside of an animal including the tail. Ventral - Relating to the underside or belly. Vertical Pupil - An elliptical pupil with its long axis vertical. Vocal Sac - Loose skin on the throat of a frog or toad which acts as a resonating chamber when the animal produces a vocal sound. (Usually single, but paired in some species.) Xanthic - Tending toward a yellow or yellowish color. Wart - A bump or growth on the skin. Xeric - of, pertaining to or adapted to a very dry habitat or environment (such as a desert.) Albino | Define Albino at Dictionary.com albino [al-bahy-noh or, esp. British, -bee-] /ælˈbaɪ noʊ or, esp.

British, -ˈbi-/ Spell noun, plural albinos. 1. a person with pale skin, light hair, pinkish eyes, and visual abnormalities resulting from a hereditary inability to produce the pigment melanin. 2. an animal or plant with a marked deficiency in pigmentation. 3. Philately. an embossed stamp accidentally left without ink. Origin of albino 1770-80; < Portuguese, equivalent to alb(o) white (< Latin albus) + -ino -ine 1 Related forms [al-bin-ik] /ælˈbɪn ɪk/ (Show IPA), albinal [al-buh-nl] /ˈæl bə nl/ (Show IPA), adjective Dictionary.com Unabridged Examples from the Web for albino Expand Contemporary Examples America's Secret Nuclear Test Revealed in Area 51 Annie Jacobsen May 12, 2011 Historical Examples Iday had the round card on which were written the forty-eight questions, while albino held the book of answers.

Marge Askinforit Barry Pain They were both speckled trout, lived side by side, ate the same food, but differed as greatly as a red-headed boy and an albino. British Dictionary definitions for albino Expand a person with congenital absence of pigmentation in the skin, eyes, and hair 2. any animal or plant that is deficient in pigment Derived Forms C18: via Portuguese from Spanish, from albo white, from Latin albus Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Word Origin and History for albino Expand n. 1777, from Spanish or Portuguese albino, from Latin albus "white" (see alb ). Used by Portuguese of white-spotted African negroes. Extended 1859 to animals having the same peculiarity.

A female albino formerly was an albiness (1808). Online Etymology Dictionary, © 2010 Douglas Harper Human Biological Adaptability: Skin Color as an Adaptation is essentially unable to tan While skin tanning is often most noticeable on light complexioned people, even those with very dark brown skin can tan as a result of prolonged exposure to the sun. Some Northwest Europeans have substantially lost the ability to tan as a result of relaxed natural selection. Their skin burns and peels rather than tans. This is due to the fact that they produce a defective form of a skin protein Mc1r (melanocortin-1 receptor) which is necessary for the production of melanin. They are at a distinct disadvantage in tropical and subtropical environments. Not only do they suffer the discomfort of readily burning, but they are at a much higher risk for skin cancer. The same is true of albinos . It would be harmful if melanin acted as a complete shield. A certain amount of shortwave ultraviolet radiation (UVB) must penetrate the outer skin layer in order for the body to produce vitamin D.

Approximately 90% of this vitamin in people normally is synthesized in their skin and the kidneys from a cholesterol-like precursor chemical with the help of ultraviolet radiation. The remaining 10% comes from foods such as fatty fish and egg yolks. Simple vitamin D is converted by our bodies into two sequential forms. The last form, commonly referred to as vitamin D3, is needed for the intestines to absorb calcium and phosphorus from food for bone growth and repair. Calcium is also necessary in adults to maintain normal heart action, blood clotting, and a stable nervous system. New evidence suggests that vitamin D may help prevent a wide range of cancers, including those of the colon and breasts. Vitamin D plays an additional important role in promoting the production of cathelicidin, which helps to defend our bodies against fungal, bacterial, and viral infections, including the common flu. Too much ultraviolet radiation penetrating the skin may cause the breakdown of folate in the body, which can cause anemia . Folate is derived from folic acid (one of the B vitamins) in our food. Pregnant women who are deficient in folate are at a higher risk of having miscarriages and babies with neural tube defects .

Because folate is needed for DNA replication in dividing cells, its absence can have an effect on many body processes, including the production of sperm cells. It may be that the ability to produce melanin was selected for in our early human ancestors because it helped preserve the body's supply of folate in addition to reducing the chances of developing skin cancer. People who live in far northern latitudes, where solar radiation is relatively weak most of the year, have an advantage if their skin has little shielding pigmentation. Nature selects for less melanin when ultraviolet radiation is weak. In such an environment, very dark skin is a disadvantage because it can prevent people from producing enough vitamin D, potentially resulting in rickets disease in children and osteoporosis in adults. Contributing to the development of osteoporosis in older people is the fact that their skin generally loses some of its ability to produce vitamin D. Women who had prolonged vitamin D deficiencies as girls have a higher incidence of pelvic deformities that prevent normal delivery of babies. The Inuit people of the American Subarctic are an exception. They have moderately heavy skin pigmentation despite the far northern latitude at which they live.

While this is a disadvantage for vitamin D production, they apparently made up for it by eating fish and sea mammal blubber that are high in vitamin D. In addition, the Inuit have been in the far north for only about 5,000 years. This may not have been enough time for significantly lower melanin production to have been selected for by nature. In the United States and other developed nations, milk is now usually fortified with vitamins D and A in order to prevent developmental problems such as those described above. However, the popularity of carbonated soft drinks and other alternatives to milk along with a decrease in the amount of time spent outdoors has led to a considerable rise in the rate of rickets disease. Not surprisingly, vitamin D deficiency is most acute in the winter in temperate and colder zones, especially among people of African ancestry. There is a growing epidemic of vitamin D deficiency in the United States. The 2007-2008 "National Government Health and Nutrition Examination Survey" found that only 23% of teens and adults had a sufficient amount of this essential vitamin in their blood. It was 45% a decade earlier. The rate for African Americans in particular was far worse.

It has dropped from 12% to only 3% having what doctors consider to be an adequate amount of vitamin D for overall good health. Given this difference, it is not surprising that 15% African American women have pelvis deformities, while the rate among European Americans is only 2%. There is also a strong correlation between the amount of sunlight that children are exposed to and whether or not they will develop multiple sclerosis as adults. Most cases of this degenerative neural disorder are in the temperate regions of the world where the sunlight is rarely intense. Children growing up in tropical and subtropical regions rarely develop MS regardless of where their ancestors came from. This protection apparently continues for those who move to far northern or far southern regions after 16 years of age. What processes are responsible for this protection from MS and its possible relationship to skin color are unknown. New research by Nina Jablonski and George Chaplin has led to the discovery that women generally produce 3-4% less melanin in their skin than do men in all populations of the world. They suggest that this is probably due to the fact that women have far higher calcium requirements during their reproductive years.

Mate selection preference and other cultural practices may also be partly responsible for this gender difference in skin coloration. Nina Jablonski breaks the illusion of skin color --explanation of why humans have a wide variation in skin color around the world. This link takes you to an external website. To return here, you must click the "back" button on your browser program. (length = 14 mins, 46 secs) Skin Color Distribution Around the World Before the mass global migrations of people during the last 500 years, dark skin color was mostly concentrated in the southern hemisphere near the equator and light color progressively increased farther away, as illustrated in the map below. In fact, the majority of dark pigmented people lived within 20� of the equator. Most of the lighter pigmented people lived in the northern hemisphere north of 20� latitude, where ultraviolet radiation is much less intense on average. (Data for native populations collected by R. Biasutti prior to 1940.) Such a non-random distribution pattern of human skin color was predicted by Constantin Wilhelm Lambert Gloger, a 19th century German zoologist.

In 1833, he observed that heavily pigmented animals are to be found mostly in hot climates where there is intense sunshine. Conversely, those in cold climates closer to the poles commonly have light pigmentation. Presumably, the relative intensity of solar radiation is largely responsible for this distribution pattern. There are exceptions to Gloger's rule in the animal kingdom. In some species the survival value of having a camouflaged body can be more important than the selective pressures of ultraviolet radiation. This is the case with arctic hares, which are white like snow in the winter and mottled black, brown, and gray similar to the rocky ground in their region after the snow melts in the summer. These color changes make it more difficult for arctic foxes to prey on them. Among humans, mate selection preferences may counter some of the evolutionary trend in skin color predicted by Gloger. Ultraviolet radiation is also blocked to some degree by hair, clothing, smog, fog, smoke, clouds, and trees. The Inuit case described earlier suggests that diet may additionally be a significant factor in some societies.

NEWS: In the February 2007 issue of the Journal of Nutrition, a research team led by Lisa Bodnar of the University of Pittsburgh School of Public Health reported that among 400 first-time pregnant women from that city who participated in their study, only 16.1% of African Americans and 52.9% of European Americans had sufficient amounts of vitamin D in their blood to be considered healthy at the end of their pregnancies. This was despite the fact that more than 90% of them had regularly taken standard doses of prenatal vitamin supplements. Tests of umbilical cord blood indicated that only 7.6% of the African American infants and 33.9% of the European American ones had adequate amounts of vitamin D at birth. The authors concluded that prenatal vitamins should include higher doses of vitamin D, especially in the northern regions of the U.S.

Question: What word describes an organism with an absence of pigment in the skin?
Answer: Albino