Terminal:
-Eyebrows, eyelashes, and scalp
-Armpit and pubic hair
-Male facial hair
Lanugo:
-Mostly found on a fetus
-Replaced by vellus
Vellus:
-90% of the hair on women
-Most of the hair on children except eyebrows, eyelashes, and scalp
-Only 10% of hair on men
Explanation:
Lanugo is fine, downy, unpigmented hair that appears on the fetus in the last 3 months of development. By the time of birth,
most of it is replaced by vellus, similarly fine, pale hair. Vellus constitutes about two-thirds of the hair of women, one-tenth of the hair of men, and all of the hair of children except for the eyebrows, eyelashes, and hair of the scalp. Terminal hair is longer, coarser, and usually more heavily pigmented.
Sebaceous:
-Secretes sebum
-Usually opens up into a hair follicle
-Coats the scalp hair with oil
-Blockage and infection can cause
pimples
Ceruminous:
-Secretes earwax
-Coats guards hairs to improve their performance
-Simple, coiled, tubular glands
-Waterproofs the ear canal
Explanation:
Ceruminous glands are found only in the external ear canal, where their secretion combines with sebum and dead epidermal cells to form earwax, or cerumen. They are simple, coiled, tubular glands with ducts leading to the skin surface. Cerumen keeps the eardrum pliable, waterproofs the canal, kills bacteria, and coats
the guard hairs of the ear, making them sticky and more effective in blocking foreign particles from entering the canal. Sebaceous glands produce an oily secretion called sebum. They are flask-shaped, with short ducts that usually open into a hair follicle, although some of them open directly onto the skin surface. These are holocrine glands with little visible lumen. Sebum keeps the skin and hair from becoming dry, brittle, and cracked.
Basal Cell
Carcinoma:
-Most common type
-Seldom spreads to other tissues
-Arises from the deepest layer of the epidermis
Melanoma:
-If metastasized, the deadliest skin cancer
-Arises from the cells that protect from UV light
-Least common type
-Caused by mutations commonly found in moles
Squamous Cell Carcinoma:
-Arises form superficial cells of the epidermis
-Raised, reddened, scaly appearance
-Can spread from the keratinocytes to the lymph nodes
Explanation:
Basal
cell carcinomais the most common type. It is the least deadly because it seldom metastasizes, but if neglected, it can severely disfigure the face. It arises from cells of the stratum basale and eventually invades the dermis. Squamous cell carcinoma arises from keratinocytes of the stratum spinosum. Lesions have a raised, reddened, scaly appearance, later forming a concave ulcer with raised edges. The chance of recovery is good with early detection and surgical removal, but if it goes unnoticed
or is neglected, this cancer tends to metastasize to the lymph nodes and can be lethal. Melanoma is a skin cancer that arises from the melanocytes. It accounts for no more than 5% of skin cancers, but it is an extremely aggressive and drug-resistant type. It can be treated surgically if it is caught early, but if it metastasizes—which it does quickly—it is unresponsive to chemotherapy and is usually fatal.