Fingernails and Toenails
clear, hard derivatives of the stratum corneum. Composed of very thin, dead cells packed with hard keratin.
allow for more fleshy and sensitive fingertips. Tools for digging, gromming, picking apart food and other manipulations.
Nail Structure - Nail Bed
skin underlying the nail plate.
Hyponychium - epidermis of the the nail bed.
Nail Structure - Nail Matrix
Growth zone of thickend stratum basale at the proximal end of nail. Mitosis here accounts for nail growth. 1mm per week in fingernails, slightly slower on toenails.
Five Glands of Skin
Merocrine sweat glands, apocrine sweat glands, sebaceous glands, ceruminous glands, mammary glands.
Sweat (sudoriferous) Glands - Merocrine
Most numerous skin glands: 3-4 million in adult skin. Simple tubular glands. Watery perspiration that helps cool the body. Myoepithelial cells - contract in response to stimulation by sympathetic nervous stem and squeeze perspiration up the duct.
Sweat (sudoriferous) Glands - Apocrine
Occur in groin, anal region, axilla, areola, bearded area in mature males. Ducts lead to nearby hair follicles. Produces sweat that is thicker, milky and contains fatty acids. Scents glands that respond to stress and sexual stimulation. Develop at puberty.
Apocrine Sweat Glands - Pheromones
Chemicals that influence the physiology of behavior of other members of the species
Apocrine Sweat Glands - Bromhidrosis
disagreeable body odor produced by bacterial action on fatty acids
Composition of Sweat
Sweat production takes place in the deep secretory portion of the gland. It is made up of sodium chloride, potassium, urea, lactic acid and ammonia. Some drugs are also excreted in the perspiration.
Flask shapped glands with short ducts opening into hair follicle. These are Holocrine Gland - secretion consists of broken down cells. Replaced by mitosis at base of gland. Keeps skin and hair from becoming dry, brittle, and cracked.
Found only in external ear canal. Their secretion combines with sebum and dead epithelial cells to form earwax (cerumen).
Ceruminous Glands - Earwax (cerumen) -Funtions
-Keeps eardum pliable. - Waterproofs the canal.
- Kills bacteria. - makes guard hairs of ear sticky to help block foreign particles from entering auditory canal. - Simple, cubodial tubula glands with ducts that lead to skin surface.
Breasts (mammae) of both sexes contain very little glandular material. Mammary glands - Milk producing glands that develop only during pregnacy and lactation. - Modified apocrine sweat gland. - Richer secretion released by ducts opening into the nipple (mammary ridge or milk lines). - Two rows of mammary glands in most mammals. - Primates kept only anteriormost glands. - Additional nipples (polythelia). - May develop along milk lines.
Skin Disorders - Skin Cancer
induced by UV rays of the sun. most often on head and neck. Most common in fair-skinned people and ederly. One of the most common cancer. One of the easist to treat. Has one the highest survival rates if detected and treated early.
Three types of skin cancer
Named for the epidermal cells in which they originate. Basal cell carcinoma, squamous cell carcinoma, malignant melanoma
Basal Cell Carcinoma
Most common type. Least dangerous because it seldom metastasizes. Forms from cells in stratum basale. Lesion is small, shiny bump with central depression and beaded edges.
Squamous Cell Carcinoma
Arise from keratinocytes from stratum spinosum. Lesions usually appear on scalp, ears, lower lip or back of the hand. Have raised, reddened, scaly appearance later forming a concave ulcer. Chance of recovery good with early detection and surgical removal. Tends to metastasize to lymph nodes and may become lethal.
Skin cancer that arises from melanocytes; often in a preexisting mole. Less than 5% of skin cancers, but most deadly form. Treated surgically if caught early. Metastasizes rapidly; unresponsive to chemotherapy; usually fatal. Person with metastic melanoma lives 6 months from diagnosis. 5% to 14% survive 5 years. Greatest risk factor; familial history of malignant melanoma. High incidence in men, redheads, people who experience severe sunburn in childhood.
UVA and UVB
Improperly called "tanning rays" and "burning rays". Both thought to inititate skin cancer.
protect you from sunburn but unsure if they provide protection against cancer. Chemical in sunscreen damage DNA and generate harmful free radicals
Leading cause of accidental death. Fires, kitchen spills, sunlight, ionizing radiation, strong acids or bases, or electrical shock. Deaths result primarily from fluid loss, infection, and toxic effects of eschar (burned, dead tissue). Debridement; removal of eschar
partial-thickness burn; involves only the epidermis. marked by redness, slight edema and pain. Heals in a few days. Most sunburns are First-degree burns.
Partial thickness burn; involves the epidermis and part of the dermis. Leaves part of the dermis intact. Red, tan, or white. Two weeks to several months to heal and may leave scars.
full-thickness burn;the epidermis and all the dermis, and often some deeper tissus (muscles or bones) are destroyed. Often requires skin grafts. Needs fluid replacement. and infection control.
Autograft (skin graft)
tissue taken from another location on the same person's body. Split-skin graft taking epidermis and part of the dermis from an undamaged area such as the thigh or buttocks and grafting it into the burned area.