In order to understand what causes skin lesions, it is instructive to learn about the structure and function of your skin. Your skin is also known as the integumentary system. This integumentary system is actually the largest organ in your body and has many functions and structures. This vital organ system protects your body from various kinds of damage including maintaining such as loss of water or abrasions from outside. Therefore your skin serves to protect your deeper tissues from dehydration and injury but your skin has many other functions. Your skin acts as a protective barrier against invading organisms that can cause infections. Your skin helps regulate your body temperature by closing and opening your pores and controlling your perspiration (which has a cooling effect when your sweat evaporates). Your skin is an excretory organ allowing you to rid your body of various waste products. Your skin and integumentary system also is a sensory organ which allows you to detect pain, sensation, pressure, and temperature. Also when the cholesterol within your skin cells comes in contact with sunlight, this is the first step in the production of vitamin D.
Your integumentary system is more than just your skin. This vital system also includes your hair, nails, and related muscle and glands.
Primary lesions Skin Legions
- Bulla – A bulla is a large vesicle described as a rounded or irregularly shaped blister containing serous or seropurulent fluid, equal to or greater than either 5 or 10 mm, depending on one's definition of a vesicle.
- Burrow – A burrow appears as a slightly elevated, grayish, tortuous line in the skin, and is caused by burrowing organisms.
- Cyst – A cyst is an epithelial-lined cavity containing liquid, semi-solid, or solid material.
- Erosion – An Erosion is a discontinuity of the skin exhibiting incomplete loss of the epidermis, a lesion that is moist, circumscribed, and usually depressed.
- Fissure – A fissure is a crack in the skin that is usually narrow but deep.
- Papule – (Solid mass) A papule is a circumscribed, solid elevation of skin with no visible fluid, varying in size from a pinhead to less than either 5 or 10 mm in diameter at the widest point.
- Pustule- (Liquid) – A pustule is a small elevation of the skin containing cloudy or purulent material usually consisting of necrotic inflammatory cells. These can be either white or red.
- Plaque – A plaque has been described as a broad papule, or confluence of papules equal to or greater than 1 cm or alternatively as an elevated, plateau-like lesion that is greater in its diameter than in its depth.
- Patch – A patch is a large macule equal to or greater than either 5 or 10 mm across, depending on one's definition of a macule. Patches may have some subtle surface change, such as a fine scale or wrinkling, but although the consistency of the surface is changed, the lesion itself is not palpable.
- Macule – A macule is a change in surface color, without elevation or depression and, therefore, non-palpable, well or ill-defined, variously sized, but generally considered less than either 5 or 10 mm in diameters at the widest point.
- Nodule – A nodule is morphologically similar to a papule, but is greater than either 5or 10 mm in both width and depth, and most frequently centered in the dermis or subcutaneous fat. The depth of involvement is what differentiates a nodule from a papule.
- Telangiectasia – A telangiectasia represents an enlargement of superficial blood vessels to the point of being visible.
- Ulcer – An ulcer is a discontinuity of the skin exhibiting complete loss of the epidermis and often portions of the dermis and even subcutaneous fat.
- Vesicle – A vesicle is a circumscribed, fluid-containing, epidermal elevation generally considered less than either 5or 10 mm in diameter at the widest point.
- Wheal – A wheal is a rounded or flat-topped, pale red papule or plaque that is characteristically evanescent, disappearing within 24 to 48 hours. The temporary raised bubble of taut skin on the site of a properly-delivered intradermal injection is also called a wheal, with the ID injection process itself frequently referred to as simply "raising a wheal" in medical texts.
- Keloid- A keloid is the formation that a type of scar which, depending on its maturity, is composed mainly of either type III (early) or type I (late) collagen. It is a result of an overgrowth of granulation tissue (collagen type 3) at the site of a healed skin injury which is then slowly replaced by collagen type
Secondary Skin Legions
- Atrophy – refers to a loss of tissue, and can be epidermal, dermal, or subcutaneous. With epidermal atrophy, the skin appears thin, translucent, and wrinkled. Dermal or subcutaneous atrophy is represented by depression of the skin.
- Crust – dried serum, pus, or blood usually mixed with epithelial and sometimes bacterial debris.
- Cherry angiomas, also known as senile angiomas- are cherry red papules on the skin containing an abnormal proliferation of blood vessels. They are the most common kind of angioma. Cherry angiomas are made up of clusters of capillaries at the surface of the skin, forming a small round papule, which may be flat topped
- Excoriation – a punctate or linear abrasion produced by mechanical means (often scratching), usually involving only the epidermis, but commonly reaching the papillary dermis.
- Ecchymosis- A broader definition of ecchymosis is the escape of blood into the tissues from ruptured blood vessels. The term also applies to the subcutaneous discoloration resulting from seepage of blood within the contused tissue.
- Induration – is a dermal thickening causing the cutaneous surface to feel thicker and firmer.
- Lichenification – is an epidermal thickening characterized by visible and palpable thickening of the skin with accentuated skin markings.
- Maceration – is a softening and turning white of the skin due to being consistently wet.
- Petechial -A Petechial (plural petechiae), is a small 1 - 2 mm red or purple spot on the body, caused by a minor hemorrhage (broken capillary blood vessels).
- Scale – dry or greasy laminated masses of keratin that represent thickened stratum corneum.
- Umbilication – is a formation of a depression at the top of a papule, vesicle, or pustule.
- Ecchymosis- is a subcutaneous purpura (extravasation of blood) larger than 1 centimeter or a hematoma, commonly, but erroneously, called a bruise. That is, bruises are caused by trauma whereas ecchymosis is a type of purpura, and are not caused by trauma.