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| A group of interacting, interrelated, or interdependent organs forming a complex functional whole; the set of organs of the body regarded as a functional physiological unit. |
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| The membranous tissue forming the external covering or integument of a human and consisting of the epidermis (stratified squamous epithelium and epidermal derivatives) and the dermis (dense irregular connective tissue; the functions of the skin include protection and immune defense, thermoregulation, sensation, communication, vitamin D synthesis, etc. |
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| The branch of medicine that is concerned with the physiology and pathology of the skin. |
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| The physiological processes of discharging waste molecules/matter (e.g., respiration, urine, sweat, particularly feces) from individual cells and from the body. |
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| The subcutaneous layer of loose connective tissue containing a varying number of fat cells found below the dermis in many regions of the body. |
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| located or placed just beneath the skin, usually within the dermis |
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| the property of returning to an initial form or state following deformation;flexibility |
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| A sheet or band of irregular dense fibrous connective tissue separating the dermis from underlying muscles, tendons, ligaments or bones. |
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| A fat-soluble vitamin occurring in several forms, especially vitamin D2 or vitamin D3; required for proper calcium absorption and metabolism and therefore for normal growth of teeth and bones; produced in the skin by ultraviolet irradiation of sterols found in milk, fish, and eggs |
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A localized thickening and enlargement of the horny layer (stratum corneum) of the skin. Also called a callosity.
The hard mineralized tissue which develops around the ends of a fractured bone during healing. |
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| Any specialized structure derived from the germinal epithelium of the epidermis including hair and hair follicles, nails, sweat glands and sebaceous glands. |
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| The series of unique genetically determined patterns of narrow, raised strips of epidermis which are located on the palms of the hands and soles of the feet which increase friction and, therefore, traction of the foot and gripping ability of the hand; skin gland pores open on the crests which leave a pattern of oil and sweat on touched surfaces which permit the identification of fingerprints, palm prints, etc.; the pattern of these ridges is regulated by heredity. |
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| The maintenance of a constant internal body temperature independent from the environmental temperature; the skin (radiates heat even when dry), sweat glands (evaporative cooling), subcutaneous adipose tissue (thermal insulation), and dermal capillary beds (adjusts blood flow to encourage or discourage radiant heat loss) play important roles in thermoregulation. |
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| The first three tissue types to differentiate in an early stage of embryonic development and from which all other more specialized tissues are later derived; specifically, ectoderm, mesoderm, and endoderm; ectodermal stem cells give rise to the epidermis and the nervous system; mesodermal stem cells give rise to muscle, skeletal tissues, and other connective tissues including blood vessels and blood, and the urogenital system; endodermal stem cells give rise to most other epithelial tissues. |
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| The outermost of the three primary germ layers of an embryo, composed of stem cells from which certain epithelial tissues, the epidermis, nervous tissue, and, in vertebrates, sense organs develop. |
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| The middle embryonic germ layer, lying between the ectoderm and the endoderm, composed of stem cells from which the connective tissues, including muscle and bone, and the urogenital and circulatory systems develop. |
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| the innermost of the three primary germ layers of an animal embryo, composed of stem cells which develop into the epithelial linings of the gastrointestinal tract, the lungs, and associated structures, the majority of epithelial tissues in the body. |
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| The outer, pigmented, protective, innervated but nonvascular layer of keratinized stratified squamous epithelium covering the dermis; the epidermis gives rise to derivatives including hair, nails, sweat and sebaceous glands |
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| The process of converting (something, e.g., epidermis, hair, nails, horns, and hooves) into keratin. |
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| The protein precursor to keratin which is the predominant form of the protein observed in keratinocytes in the stratum granulosum of the epidermis of the skin. |
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| A tough, insoluble protein, produced by keratinocytes, which is the predominant form of the protein in the stratum lucidum and stratum corneum of the skin; it helps protect the epidermis from abrasion and water loss; keratin is also the chief structural constituent of hair, nails, horns, and hooves. |
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| The vast majority of cells comprising the stratified squamous epithelium of the epidermis which produce keratin and then die, forming the protective outer layers of the skin which are continually being sloughed; these tightly packed cells are held together by desmosomes. |
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| A small set of spider-shaped epidermal cells restricted to the stratum germinativum (10 - 25% of the basal cells) which synthesize the brown/black pigment melanin and then package the melanin in melanosomes which are transferred to keratinocytes; their melanin output is determined by an individual's heredity and by the environmental stimulus of exposure to uv radiation from sunlight; these are the cells of origin for malignant melanoma cnacers. |
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| epidermal dendritic cell = Langerhans' cell |
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| A star-shaped wandering macrophage derived from the bone marrow which infiltrate the epidermal layers and serve the immune functions of phagocytosis and antigen-presentation. |
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| An exteroreceptor located in the stratum germinativum of the epidermis; a small receptor resembling a spiky hemisphere which communicates with the disk-like sensory terminal of a neuron; the combined structure is termed a Merkel or tactile disc; they are receptors for light or discriminative touch. |
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| stratum basale = stratum germinativum |
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Definition
| he basal layer of the stratified squamous epithelium of the epidermis which consists primarily of the youngest cuboidal keratinocytes which are undergoing mitosis to produce the rest of the keratinocyte layers of the epidermis, as well as a few melanocytes, Merkel cells, and epidermal dendritic = Langerhans' cells; this layer is the site of origin for basal cell carcinoma cancers. |
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| The second deepest layer (from the basal layer) of the stratified squamous epithelium of the epidermis, several cell layers thick, which consists primarily of developing irregularly-shaped keratinocytes ("prickle cells") which are synthesizing prekeratin filaments. |
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| The third deepest layer (from the basal layer) of the stratified squamous epithelium of the epidermis, three to five cell layers thick, which consists primarily of flattening spindle-shaped keratinocytes which are synthesizing keratinohyaline and water-proofing glycolipids. |
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| The fourth deepest layer (from the basal layer) of the stratified squamous epithelium of the epidermis, a few cell layers thick (the "clear layer") located between the stratum granulosum and the stratum corneum, which only appear in the thick skin of the palms of the hands and soles of the feet, which consists primarily of flattening dead keratinocytes which have a relatively clear cytoplasm. |
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| The outer protective layer ("horny layer") of the stratified squamous epithelium of the epidermis, 20 to 30 cell layers thick, which consists primarily of flattened dead keratin-filled keratinocytes which are regularly sloughed in response to friction. |
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| An epidermal derivative produced by the hair follicle in the dermis of the skin; the cylindrical, keratinized, often pigmented protein filaments characteristically growing from the epidermis of a mammal, composed of an exposed shaft and an embedded root; their length and thickness varies over the body surface based on function; they function in thermoregulation (evaporative cooling), communication, sensory reception, dry lubrication where the limbs extend from the trunk, secondary sexual characteristic, etc.; growth patterns are regulated by heredity, sex hormones, nutrition and health status. |
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| The inner core of an internal organ or body structure; e.g., the interior of the hair shaft which contains soft keratin. |
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| The outer layer of an internal organ or body structure; e.g., the exterior of the hair shaft (which is covered by a thin layer of waterproof cuticle) which contains hard keratin and pigments |
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| The tubular infolding of the epidermis containing the root of a hair and the supporting sheath and bulb and to which are attached a sebaceous gland and an arrector pili muscle. |
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| The lower expanded section of the root of a hair which fits like a cap over the hair papilla; it is located at the bottom of the hair follicle and it contains the cells from which the hair shaft develops. |
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| The small nipplelike projection or protuberance of areolar connective tissue at the base of the bulb portion of the root of a hair which brings the capillary blood supply closer to the epidermal cells involved in the synthesis of the growing hair shaft. |
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| The short strand of involuntary smooth muscle that extends from the side of a hair follicle on which the sebaceous gland is located to the basement membrane of the nearby epidermis; when contracted the action of the muscle causes the hair shaft to stand more erect; contraction of the muscle is stimulated by exposure to cold or as a result of emotional upsets, e.g., anger or fear. |
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| A complex sensory exteroreceptor for fine touch consisting of a network of sensory nerve endings wrapped about the bulb of each hair follicle; external movements of the hair shaft stimulate the receptor. [aka hair follicle receptor] |
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| An epidermal derivative produced at the dorsal surface of the distal phalanges (fingers and toes) which consists of a flattened plate of densely packed keratinized cells, used to improve the grasp of the fingers and to protect the tips of the digits. |
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| The sensitive (innervated) dense irregular fibrous connective tissue layer of the skin located below the epidermis, containing nerve endings, hair follicles, sweat and sebaceous glands, and blood and lymph vessels. |
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| The superficial ~20% of the dermis, between the epidermis and the reticular region, which consists of highly vascular loose (areolar) connective tissue; named for the presence of the dermal papillae which increase the surface area of contact with the epidermal basal layer to facillitate nutrient and waste exchange between the two tissues. |
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| The series of bulges of the papillary region of the dermis of the skin increase the surface area under the epidermis to facilitate diffusion of nutrients, oxygen and wastes between the basal layers of epidermal cells and the blood. |
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| the deeper ~80% of the dermis, beneath the papillary region, which consists of dense irregular connective tissue. |
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| A group of specialized sensory receptors composed of a relatively rounded globular mass of cells, located in the dermis, or rarely the epidermis, which respond to varying degrees of mechanical pressure or vibrations. |
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| tactile corpuscle = Meisner's corpuscle |
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Definition
| An exteroreceptor located in the dermal papillae, especially in sensitive hairless areas such as the palms of the hands, soles of the feet, and nipples; a small receptor consisting of a few spiraling sensory terminals surrounded by Schwann cells and a thin egg-shaped connective tissue capsule; they are receptors for light or discriminative touch. |
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| lamellated corpuscle = Pacinian corpuscle |
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| An exteroreceptor scattered deep in the dermis and subcutaneous tissues; a large receptor consisting of a sensory dendrite surrounded by layers of flattened cells and layers of collagen fibers forming an egg-shaped capsule; they are receptors for vibration. |
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| Any of a group of naturally occurring insoluble dark (brown to black) protein pigments, found in the skin (brown to black) and hair (brown to black to red to orange), produced by specialized epithelial cells = melanocytes of the stratum germinativum and distributed to other epithelial cells, the keratinocytes; production of the pigment is stimulated by exposure to uv light; the pigment is also found in the external layer of the retina, in the outer layer of the choroid, and elsewhere in the body; melanin generally serves to prevent light from penetrating to deeper tissues; this is especially important in the skin for reducing mutagenic uv light penetration to deeper tissues; the pattern of melanin deposition is regulated by heredity while the concentration of the pigment is regulated by a combination of heredity and environment (uv light exposure). |
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| An orange-yellow to red crystalline fat-soluble pigment [C40H56] found in animal tissues and certain plants, such as carrots and squash; it exists in several isomeric forms and is converted to vitamin A in the liver. |
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| The iron-containing respiratory pigment in red blood cells of vertebrates, consisting of about 6 percent heme (lipid) and 94 percent globin (protein (2 alpha and 2 beta chains)); in arterial blood, it is always combined with oxygen, and is then called oxyhemoglobin; it functions primarily to transport oxygen from the lungs to the body tissues and is also a significant buffer of the blood. |
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| Any normal small brownish to orange spot on the skin, often turning darker or increasing in number upon exposure to the sun, caused by an increase in melanin deposition |
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| Congenital absence of any melanin pigmentation or coloration in a person, due to an hereditary defect in an enzyme in the melanin synthesis pathway, resulting in pale skin, white hair and pink eyes. |
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| A rare* acquired, possibly autoimmune, skin disease exhibiting a reduction in melanocytes and the resulting development of smooth, milk-white spots or patches of unpigmented skin (often surrounded by a heavily pigmented border) upon various parts of the body; hair in the affected areas is usually, but not always, white. [* Vitiligo is the most common skin pigmentation disorder.] |
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| The unnatural lack of color in the skin (as from bruising or sickness or emotional distress); generally the reduction in color is due to less red hemoglobin being routed through the subcutaneous capillary beds, e.g., in a person exposed to cold, or in certain emotional states such as fright or pain, or there may be a systemic anemia. |
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| A bluish discoloration of the skin and mucous membranes resulting from inadequate oxygenation of the blood; this color change is often a symptom of cardiovascular or respiratory disease; in dark-skinned individuals, it may be best observed on the mucous membranes, e.g., of the eyes or mouth, or in the nail beds at the finger tips. |
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| Yellowish discoloration of the whites of the eyes, skin, and mucous membranes (and of the urine) caused by the accumulation in these tissues of bilirubin (a lipid-soluble breakdown product of the heme groups in hemoglobin); it occurs as a symptom of various diseases, such as hemolytic disorders, hepatitis and other liver diseases, and with obstruction of the bile duct system. |
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| Redness of the skin caused by dilatation and congestion of the capillaries, often a sign of inflammation or infection. |
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| sebaceous glands = skin oil glands |
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| An epidermal derivative, the small subcutaneous exocrine glands, usually connected with hair follicles which secrete sebum, an oily semifluid material, composed in large part of lipids, which softens, prevents the drying of, and lubricates the hair and skin. |
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| The oily semifluid secretion of the sebaceous glands, consisting chiefly of lipids, keratin, and cellular material; with perspiration it moistens and protects the skin. |
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| sudoriferous glands = sweat glands |
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| An epidermal derivative, the small convoluted tubular exocrine glands which are situated in the subcutaneous tissues and discharge by minute orifices onto the surface of the skin; the secretion is regulated by the autonomic nervous system; the sweat is a plasma filtrate which serves in thermoregulation through evaporative cooling and the salty, slightly acid residue left behind has mild antibacterial properties. |
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| The predominant type of sweat gland found in the skin of most parts of the body, especially numerous on the palms, the soles of the feet and the forehead, play a major role in evaporative cooling (thermoregulation). [aka merocrine sweat glands] |
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| The minority of sweat glands, with a distribution limited to axillary and anogenital regions; they have almost no role in thermoregulation, instead they begin functioning at puberty and secrete in response to sympathetic autonomic nervous system commands related to stress, e.g., anger or fear, or during sexual arousal; their secretion is also regulated by the endocrine system, e.g., steroid sex hormones. |
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| An epidermal derivative, a pair of highly specialized sweat glands, located on the anterior thoracic wall, which secrete milk to nourish the newborn; these glands are regulated by estrogens, prolactin and oxytocin. |
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| An epidermal derivative, highly specialized sweat = sudoriferous glands, located in the external ear canal which produce a protective secretion, cerumen = earwax which discourages insects from entering the external ear canal. |
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| The secretion of the ceruminous glands, a yellow or orange sticky, bitter, waxy substance which assists in protecting the external ear canal from invasion by ectoparasites (insects). [Note: in the figure on the right, above, a cerumen blockage is illustrated. But that also gives you the general area where ceruminous glands are present.] |
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| A surgical graft of healthy skin (primarily epidermis) from one part of the body to another or from one individual to another in order to replace damaged or lost skin. |
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| A tissue or organ grafted into a new position in or on the body of the same individual; the most desirable source for skin grafting in burns, if possible, because no rejection will occur. |
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| A graft of tissue that is obtained from a donor genetically identical to the recipient for which no rejection will occur. |
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| A tissue or organ transplanted from a donor of the same species but different genetic makeup; the recipient's immune system must be suppressed to prevent rejection of the graft. |
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| A type of tissue graft in which the donor and recipient are of different species; most often restricted to temporary grafting (as in cases of severe burns) because the recipient's immune system must be suppressed to prevent rejection of the graft. |
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| An injury to tissue produced by fire, heat, friction, radiation, electricity, or a caustic agent; burns are classified according to their severity as determined by how many tissue layers (epidermis, dermis, hypodermis, deeper tissues) are involved and by the extent and character of the lesion (inflamed - inflamed and blistered - inflamed, blistered and charred). |
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| A mild burn that produces redness/inflammation of the skin but no blistering; epidermal damage only; burns may be caused by high temperature materials, fire, electricity, caustic chemicals, certain kinds of abrasion, and by radiation (uv, x-ray, etc.). |
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| A burn that blisters the skin and is more severe than a first-degree burn; epidermal and some dermal damage; burns may be caused by high temperature materials, fire, electricity, caustic chemicals, certain kinds of abrasion, and by radiation (uv, x-ray, etc.). |
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| An alternative category for classifying burns which includes both first- and second-degree burns; epidermal and, perhaps, some dermal damage; burns may be caused by high temperature materials, fire, electricity, caustic chemicals, certain kinds of abrasion, and by radiation (uv, x-ray, etc.). |
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| A severe burn in which the skin and underlying tissues are destroyed and sensitive nerve endings are exposed; severe epidermal and dermal damage as well as some damage to subcutaneous and even deeper tissues; burns may be caused by high temperature materials, fire, electricity, caustic chemicals, certain kinds of abrasion, and by radiation (uv, x-ray, etc.). |
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| An alternative category for classifying burns which includes the third-degree burns; severe epidermal and dermal damage as well as some damage to subcutaneous and even deeper tissues. |
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| A method used clinically to roughly estimate the amount of fluid lost from a burn patient by computing the percentage of body surface burned; the body is divided into 11 areas, each accounting for 9% of the total body area, and a 12th area representing the 1% of body surface occupied by the genitals. |
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| A scraped area on the skin or on a mucous membrane, resulting from a friction-induced injury or irritation, which penetrates beneath the epidermis (epithelium). |
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| An inflammatory disease of the sebaceous glands and hair follicles of the skin that is marked by the eruption of pimples or pustules, especially on the face. |
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| A skin condition marked by an overgrowth of layers of rough, gritty or scaly skin, more common in fair-skinned or elderly individuals; the lesions are abnormally sensitive to the effects of uv light (sunlight) and approximately one in five lesions will progress to squamous cell carcinoma. |
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| A chronic ulcer of the skin (the epidermis, dermis and sometimes deeper tissues) caused by prolonged pressure and reduced blood supply to a region over a bony prominence such as the hip or heel (as in bedridden patients); aka bedsore. |
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| A very common and the least malignant skin cancer in which cells of the stratum germinativum proliferate, invading the dermis and hypodermis; the lesions are slow-growing shiny raised nodules most occurring on skin regions exposed to the sun. |
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| A malignant (invasive and potentially metastatic) carcinoma that arises from squamous epithelium which generally produces an ulcerated hardened lesion; it is among the most common form of skin cancer. |
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| A malignant (invasive and potentially metastatic) carcinoma that arises from epidermal melanocytes which generally produces a raised hardened pigmented lesion; it is the most difficult to successfully treat of the skin cancers. |
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