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the outer covering of the body. The skin is the largest organ of the body, and it performs a number of vital functions. It serves as a protective barrier against microorganisms. It helps shield the delicate, sensitive tissues underneath from mechanical and other injuries. It acts as an insulator against heat and cold, and helps eliminate body wastes in the form of perspiration. It guards against excessive exposure to the ultraviolet rays of the sun by producing a protective pigmentation, and it helps produce the body's supply of vitamin D. Its sense receptors enable the body to feel pain, cold, heat, touch, and pressure. The skin consists of two main parts: an outer layer, the epidermis, and an inner layer, the corium (or dermis).

Epidermis. The epidermis is thinner than the corium, and is made up of several layers of different kinds of cells. The number of cells varies in different parts of the body; the greatest number is in the palms of the hands and soles of the feet, where the skin is thickest.

The cells in the outer or horny layer of the epidermis are constantly being shed and replaced by new cells from its bottom layers in the lower epidermis. The cells of the protective, horny layer are nonliving and require no supply of blood for nourishment. As long as the horny outer layer remains intact, microorganisms cannot enter.
Corium. Underneath the epidermis is the thicker part of the skin, the corium, or dermis, which is made up of connective tissue that contains blood vessels and nerves. It projects into the epidermis in ridges called papillae of the corium. The nerves that extend through the corium end in the papillae. The various skin sensations, such as touch, pain, pressure, heat, and cold, are felt through these nerves. The reaction to heat and cold causes the expansion and contraction of the blood capillaries of the corium. This in turn causes more or less blood to flow through the skin, resulting in greater or smaller loss of body heat (see temperature).

The sweat glands are situated deep in the corium. They collect fluid containing water, salt, and waste products from the blood and carry it away in canals that end in pores on the skin surface, where it is deposited as sweat. Perspiration helps regulate body temperature as well, because cooling of the skin occurs when sweat evaporates. The sebaceous glands are also in the corium. They secrete the oil that keeps the skin surface lubricated.

Beneath the corium is a layer of subcutaneous tissue. This tissue helps insulate the body against heat and cold, and cushions it against shock.

The hair and nails are outgrowths of the skin. The roots of the hair lie in follicles, or pockets of epidermal cells situated in the corium. Hair grows from the roots, but the hair cells die while still in the follicles, and the closely packed remains that are pushed upward form the hair shaft that is seen on the surface of the skin.

The nails grow in much the same way as the hair. The nail bed, like the hair root, is situated in the corium. The pink color of the nails is due to their translucent quality which allows the blood capillaries of the corium to show through.
Normal skin. From Frazier et al., 2000.
skin test application of a substance to the skin, or intradermal injection of a substance, to permit observation of the body's reaction to it. Such a test detects a person's sensitivity to such allergens as dust and pollen, or to preparations of microorganisms believed to be the cause of a disorder.

There are several types of skin tests, including the patch test, the scratch test, and the intradermal test.
Patch Test. This is the simplest type of skin test. A small piece of gauze or filter paper is impregnated with a minute quantity of the substance to be tested and is applied to the skin, usually on the forearm. After a certain length of time the patch is removed and the reaction observed. If there is no reaction, the test result is said to be negative; if the skin is reddened or swollen, the result is positive.

The patch test is used most often in testing for skin allergies, especially contact dermatitis.
Scratch Test. In this test, one or more small scratches or superficial cuts are made in the skin, and a minute amount of the substance to be tested is inserted in the scratches and allowed to remain there for a short time. If no reaction has occurred after 30 minutes, the substance is removed and the test is considered negative. If there is redness or swelling at the scratch sites, the test is considered positive.

The scratch test is often used in testing for allergies. A complete screening for allergic sensitivity may require numerous skin tests. Only an extremely minute quantity of the substance can be used in each test since severe allergic reactions can occur.

The scratch test is also used in the diagnosis of tuberculosis. In Pirquet's reaction, for example, tuberculin is used, and the local inflammatory reaction that results is more marked in tuberculous persons than in normal ones.
Intradermal Tests. In these tests, the substance under study is injected between the layers of skin. Intradermal tests are used for diagnosis of infectious diseases and determination of susceptibility to a disease or sensitivity to an allergen.

In the intradermal test for tuberculosis, the Mantoux test, a purified protein derivative (PPD), prepared from tubercle bacilli, is injected. In a positive result, the area becomes reddened or inflamed within 72 hours. This indicates past or present infection with or exposure to the tubercle bacillus. An infection that has been present for at least 2 to 8 weeks will usually be revealed by the test.

The Schick test is used to determine susceptibility to diphtheria. A very small dose of diphtheria antitoxin is injected into the forearm. In a positive reaction the area becomes red and remains so for about a week. If no reaction occurs, the person is immune to the disease.

The trichophytin test is sometimes used in diagnosing suspected cases of superficial fungus infection of the skin, such as ringworm. In the presence of infection by the fungus Trichophyton, an injection of trichophytin, which is prepared from cultures of the fungus, will produce a reaction similar to the tuberculin reaction. Skin tests, of course, are always made in an area separate from the infected area.

In addition to their frequent use in testing for allergies, intradermal tests are employed in the diagnosis of parasitic infections, such as schistosomiasis, other fungus diseases besides trichophytosis, and mumps.


(skin), [TA]
The membranous protective covering of the body, consisting of the epidermis and dermis (corium).
Synonym(s): cutis [TA]
[A.S. scinn]


(skin) the outer protective covering of the body, consisting of the dermis (or corium) and the epidermis.
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Diagram of a cross-section of the skin.

elastic skin  Ehlers-Danlos syndrome.
farmers' skin  actinic elastosis.
lax skin , loose skin cutis laxa.
sailors' skin  actinic elastosis.


The membranous tissue forming the external covering or integument of an animal and consisting in vertebrates of the epidermis and dermis.
v. skinned, skinning, skins
To bruise, cut, or injure the skin or surface of: She skinned her knee.


Etymology: AS, scinn
the tough, supple cutaneous membrane that covers the entire surface of the body. It is composed of a thick layer of connective tissue called the dermis and an epidermis made of five layers of cells. Skin color varies according to the amount of melanin in the epidermis. Genetic differences determine the amount of melanin. The ultraviolet rays of the sun stimulate the production of melanin, which absorbs the rays and simultaneously darkens the skin. Modified skin continues into various parts of the body, such as mucous membrane, as in the lining of the vagina, the bladder, the lungs, the intestines, the nose, and the mouth. Mucous membrane lacks the heavily keratinized layer of the outside skin. The skin helps to cool the body when the temperature rises by radiating the heat of increased blood flow in expanded blood vessels and by providing a surface for the evaporation of sweat. When the temperature drops, the blood vessels constrict and the production of sweat diminishes. Also called cutaneous membrane, integument. See also dermis.


Vox populi adjective Cutaneous noun Anatomy Cutis The outer integument of the body which consists of epidermis and dermis, the latter of which rests on subcutaneous tissue. See Aging skin, Artificial skin, Blue skin, Cigarette-paper skin, Composite cultured skin, Diamond skin, Elephant skin, Glossy skin, Harlequin skin, Hide-bound skin, Leopard skin, Lizard skin, Moleskin, Moroccan leather skin, Paper money skin, Red skin, Sandpaper skin, Second Skin®, Spray-on skin, Swiss cheese skin, Washerwoman skin.


(skin) [TA]
The membranous protective covering of the body, consisting of the epidermis and corium (dermis).
Synonym(s): cutis [TA] .
[A.S. scinn]


Enlarge picture
The organ that forms the outer surface of the body. It shields the body against infection, dehydration, and temperature changes; provides sensory information about the environment; manufactures vitamin D; and excretes salts and small amounts of urea.

Skin consists of two major divisions: the epidermis and the dermis. Depending on its location and local function, skin varies in terms of its thickness, strength, presence of hair, nails, or glands, pigmentation, vascularity, nerve supply, and keratinization. Skin may be classified as thin and hairy or thick and hairless (glabrous). Thin hairy skin covers most of the body. Glabrous skin covers the surface of the palms of the hands, soles of the feet, and flexor surfaces of the digits. See: illustration; hair for illus; burn; dermatitis; dermis; eczema; epidermis; rash

alligator skin

Severe scaling of the skin with formation of thick plates resembling the hide of an alligator. See: ichthyosis

artificial skin

Human skin equivalent.

bronzed skin

Brownish hyperpigmentation of the skin, seen in Addison's disease and hemochromatosis, some cases of diabetes mellitus, and cirrhosis.

deciduous skin


elastic skin

Ehlers-Danlos syndrome.

foreign bodies in the skin

Objects that enter the skin accidentally or are inserted deliberately. The areas involved are cleaned carefully. Foreign material can be removed carefully piece by piece or by vigorous swabbing with gauze or a brush and a soapy solution. A sterile dressing should be used.

For removal of a small foreign body, the area is cleaned first with mild soap and warm water. A clean needle can be sterilized by heating it to a dull or bright red in a flame; this can be done with a single match. Because both ends of the needle get hot, it is wise to hold the far end in a nonconductor such as a fold of paper or a cork. The needle is allowed to cool. A black deposit on its surface should be disregarded; it is sterile carbon and does not interfere with the procedure. The needle is introduced at right angles to the direction of the sliver, and the sliver is lifted out. Most people attempt to stick the needle in the direction of the foreign body and consequently thrust many times before they manage to lift the sliver out. When the sliver is removed, an antiseptic is applied and the wound covered with a sterile dressing. Tetanus antitoxin or a tetanus booster may be required, depending on the history of immunization.

glabrous skin

Skin that does not contain hair follicles, such as that over the palms and soles.

glossy skin

Shiny appearance of the skin due to atrophy or injury to nerves.

hidebound skin


loose skin

Hypertrophy of the skin.

parchment skin

Atrophy of the skin with stretching.

photoaged skin

Skin changes caused by chronic sun exposure. This condition is prevented by avoiding suntanning and sunburning and has been treated with topical tretinoin and chemical peels.
Synonym: photodamaged skin

photodamaged skin

Photoaged skin.

piebald skin


scarf skin

The cuticle, epidermis; the outer layer of the skin.

sun-damaged skin

Photoaged skin.

tissue-engineered skin

Human skin equivalent.

true skin



The body's outer covering. The skin is a major organ, of area 5–6 m2. It is self-regenerating, self-lubricating and self-repairing and provides heat regulation. It is sensitive to touch, pressure, pain and temperature. It protects against solar radiation and bacterial infection and synthesizes vitamin D. The lower layer, the true skin (corium) is living, the outer layer (epidermis) has an external layer of dead, flattened horny cells.
Fig. 285 Skin. A section of the human skin showing the for a larger image
Fig. 285 Skin . A section of the human skin showing the dermis.


an organ that forms the outer covering of an animal that is external to the main musculature, often bearing scales, hair or feathers. Skin is the most widespread organ of the body and consists of an EPIDERMIS derived from the embryonic ECTODERM, and a DERMIS originating from a MESODERMIS. The epidermis is often hardened and covered by a cuticle, but may be only one cell thick.

The subcutaneous fat of the dermis acts as insulation and reduces heat loss. Heat is also conserved by the skin in cold conditions by contraction of the superficial blood vessels which diverts blood to lower layers of the skin. In some structures, such as the ear, special shunt vessels occur which dilate in cold conditions and pass blood directly from arterioles to venules, thus bypassing the superficial capillaries to reduce heat loss.

The skin. Meissner's corpuscles serve touch sensation (named after the 19th-century anatomists who described them). Pacinian corpuscles serve pressure and vibration sensation (named after the 19th-century anatomists who described them).


human skin serves the functions of sensation, protection and insulation and has a major role in regulation of body temperature, by variations in heat loss or conservation (increasing loss by vasodilatation and sweating, decreasing it by vasoconstriction), under the control of the autonomic nervous system. Sensory nerve endings and receptors include those that mediate the sensations of touch, pain and pressure.


; cutis tissue investing the entire body, and in modified form lining the gut and respiratory systems; largest organ of the body; formed of four layered structures: epidermis, basement membranous zone, dermis, subcutaneous layer (Figure 1; Table 1 and Table 2)
Figure 1: Structure of the skin.
Table 1: Constituents of skin
EpidermisStratified squamous epithelium formed from keratinocytes
Basal layer: keratinocytes linked by desmosomal and hemidesmosomal and filamentous connections (cytoskeleton; prevents shear)
Spinous layer: keratinocytes shrink, retaining contact only at desmosomes and hemidesmosomes
Granular layer: keratinocytes secrete complex lipids which act as a semipermeable skin barrier
Corneal layer: cell and contents have become keratin to form squames moved towards the exterior
Epidermal cellsKeratinocytes
Melanocytes: lie between keratinocytes; secrete pigment and protect keratinocyte nuclei from ultraviolet radiation
Merkel cells: sensory cells
Langerhans cells: within spinous layer; antigen-presenting cells
Basement membrane zoneCollagen, hemidesmosomes, laminin which aid adhesion of epidermis to dermis; dysfunctional in disease such as epidermolysis bullosa
DermisMesodermal tissue containing blood vessels, nerve, muscle, skin appendages (sweat glands, sebaceous glands, hair follicles), immune cells (histamine-releasing mast cells) in a matrix of collagen, elastin and hyaluronic acid
Subcutaneous layerAdipose tissue, blood vessels and nerves, acting as an insulating layer
Table 2: Functions of skin
FunctionSkin constituent subserving that function
Physical barrier against friction and shearing forcesKeratinization of stratum corneum; undulating dermoepidermal junction; dermofibrillar and desmosomal links
Protective barrier to infectionIntact skin layer; desquamation; acid mantle; inflammatory response
Prevention of excessive water loss or absorptionIntact waterproof keratinized outer layer
Synthesis of vitamin DSunlight-induced formation of cholecalciferol (vitamin D3) from 7-dehydrocholesterol
Temperature regulationAutonomic regulation of blood flow through skin capillaries and arterioles
Environmental awarenessSpecialized skin nerve endings (Merkel's discs, Meissner's corpuscles, pacinian corpuscles, Ruffini endings, free nerve endings) subserve pain, touch, temperature, vibration, pressure, stereognosis
Antigen presentationLangerhans cells
Immunological reactionsKeratinocytes release cytokines
Wound healingCellular elements of the dermis and epidermis
Protection from ultraviolet lightMelanosomes inject melanin granules into local keratinocytes to form a protective cap over the nucleus


(skin) [TA]
Membranous protective body covering, consisting of epidermis and dermis (corium).
Synonym(s): cutis [TA] .
[A.S. scinn ]


n the tough, supple cutaneous membrane that covers the entire surface of the body. It is the largest organ of the body and is composed of five layers of cells in the epidermis, which overlies the dermis. See also stratum.


the outer covering and largest organ of the body. It serves as a protective barrier against microorganisms, helps shield delicate tissues underneath from mechanical and other injuries, insulates against heat and cold, and helps eliminate body wastes. It guards against ultraviolet radiation by producing a protective pigment and it helps produce vitamin D. Its sense receptors detect pain, cold, heat, touch and pressure.
The skin consists of an outer cellular, avascular epidermis, and an inner fibrous corium (dermis, true skin) resting upon a hypodermis of fat and panniculus muscle.
See also cutaneous, epidermal, epidermis.
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Basic structure of the skin. By permission from McCurnin D, Poffenbarger EM, Small Animal Physical Diagnosis and Clinical Procedures, Saunders, 1991

skin appendages
skin-associated lymphoid tissues (SALT)
see skin-associated lymphoid tissue.
autoimmune skin disease
skin biopsy
removal of a small section of skin for histopathological examination. See also keyes punch.
skin cancer
include squamous cell carcinoma, papilloma and fibropapilloma, intracutaneous cornifying epithelioma (keratoacanthoma), basal cell tumors and tumors of the adnexa, perianal gland and hair follicles.
congenital absence of skin
see epitheliogenesis imperfecta.
skin depigmentation
skin emphysema
see subcutaneous emphysema.
skin fold thickness
a measure of obesity in humans but not a valid indicator in dogs or cats as the skin lifts off the subcutaneous tissue.
skin fungal infection
skin gangrene
death of tissue and usually involves dermis, epidermis and subcutaneous tissue, e.g. severe saddle galls, heat burns, chemical burns, Claviceps purpurea poisoning. The affected area is cold and bluish in color. This changes to black and the area begins to lift at the edges and to dry out.
skin inflammation
skin leukosis
occurs in marek's disease. Called also cutaneous lymphosarcoma.
skin-maggot fly
see cordylobiaanthropophaga.
skin memory
skin receptor
cutaneous sensory endorgans.
skin resiliency test
see skin tenting test (below).
skin tag
see fibrovascular papilloma.
skin tension lines
see tension line.
skin tenting test
a fold of skin is picked up and then quickly let go. The amount that it will stretch is an indication of its extensibility. The speed with which it returns to a normal position is determined by the degree of hydration of the skin and subcutaneous tissue and the amount of fat in the subcutaneous tissue, e.g. in an animal that is 10 to 12% dehydrated the skin fold will not disappear until 20 to 45 seconds have elapsed.
Enlarge picture
Tenting of the skin in a dehydrated cow. By permission from Blowey RW, Weaver AD, Diseases and Disorders of Cattle, Mosby, 1997
skin test
application or intradermal injection of a substance to the skin to test the body's reaction to it. Such a test detects an animal's sensitivity to such allergens as dust and pollen, or to preparations of microorganisms believed to be the cause of a disorder.
There are several types of skin tests, including the patch test, the scratch test, and the intradermal test.
skin wool
scoured wool from a fellmonger.

Patient discussion about skin

Q. What are the causes of viral blisters on the skin? For a few months now I've been having these hard viral blisters on my fingers. The only way to get rid of them is with freezed carbon. It does go away with that treatment- after a few weeks but then a new one appears. How can I prevent it from "attacking" again??

A. These viral blisters you are describing are caused by HPV (papilloma virus), and are very hard to get rid of without treatment with freezed carbon. Many of us have the virus but not everyone gets the actual infection. There is not a proved way of preventing from it to happen again after treatment, unfortunately..

Q. anyone knows how to stop hard skin on the feet from becoming cracked??? during summer my feet got lots of hard skin and in the heel area the skin actually got cracked kinda deep. it hurts now and the cracks are starting to get infected I guess... do u guys know how to solve this?? I know there are some creams for that but I thought maybe now it's too late for that and I need something stronger?

A. There are good creams for moisterizing the skin of your feet on a daily basis, however now that you feel they might be infected you should see a dermatologist for some better treatment.

Q. How can you know if a mole is a skin cancer or not? I'm only 15, but I’ve had this small thing on my right shoulder for a reeeeaaaally long time. It's the same color as my skin. It’s smaller than the head of a pencil eraser, perfectly round, and its smooth. I've never worried about it seriously, until about a week ago, when I read an article in a magazine about skin cancer. Even then I wouldn't have worried about it, because It didn't really match any of the symptoms, except one. It did bleed once about 2 1/2 years ago. And it said bleeding was a big sign I don't know, what do you think? And please try and say something other than," go have it checked out". Because I currently have no insurance. Thanks :]

A. If I’m not mistaken- there are clinics that do free checkups for skin cancer. I know that in my town there are couple. Here is a link I got when I googled “do free checks for skin cancer”:
look for one near your home.

More discussions about skin