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Fingernails and Toenails

clear, hard derivatives of the stratum corneum. Composed of very thin, dead cells packed with hard keratin.

Flat Nails

allow for more fleshy and sensitive fingertips. Tools for digging, gromming, picking apart food and other manipulations.

Structures of Nails

Nail plate, Nail fold, Nail goove, Nail bed, Nail matrix, Eponychium (cuticle).

Nail Structure - Nail Plate

Hard part of the nail. Includes: Free Edge, nail body, Nail root

Nail Structure - Nail Plate - Free Edge

overhangs the fingertips

Nail Structure - Nail Plate - Nail Body

visible attached part of nail

Nail Structure - Nail Plate - Nail Root

extends proximally under overlying skin

Nail Structure - Nail Fold

surrounding skin rising a bit above the nail

Nail Structure - Nail Groove

separates nail fold from nail plate

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.

Nail Structure - Nail Matrix - Lunule

an opaque white crescent at proximal end of nail

Eponychium (cuticle)

narrow zone of dead skin commonly overhangs this end of the nail

Five Glands of Skin

Merocrine sweat glands, apocrine sweat glands, sebaceous glands, ceruminous glands, mammary glands.

Sweat (sudoriferous) Glands

Merocrine (eccrine), Apocrine

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.

Sebaceous Glands - Sebum

oily secretion produced by sebaceous glands

Sebaceous Glands

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.

Sebaceous Glands - Lanolin

Sheep sebum

Ceruminous Glands

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.

Mammary Glands

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.

Malignant Malanoma

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.


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

Burn Classifications

First degree, Second Degree, Third Degree.

First-Degree Burn

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.

Second-Degree Burn

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.

Third-Degree Burn

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.

Graft options for Third Degree Burns

Autograft, isograft, temporary

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.

Isograft (skin graft)

skin from identical twin

Temporary Graft/Immune System Rejection (skin graft)

Homograft (allograft) -from unrelated person
Heterograft (xenograft) - from another species
Amnion from afterbirth
Artificial skin from silicone and collagen

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