Chapter 6 (4)

• The skin has five types of glands: merocrine sweat glands, apocrine sweat glands, sebaceous glands, ceruminous glands, and mammary glands.
• Two kinds of sweat (sudoriferous) glands: are Apocrine and Merocrine.
• Locations of Apocrine sweat glands: groin, anal region, axilla, areola, and beard area in men. It is inactive until puberty. The ducts lead to nearby hair follicles. It produces sweat that is milky and contains fatty acids. It responds to stress and sexual stimulation and is believed to secrete pheromones (chemicals that can influence the behavior of others). Bromhidrosis is disagreeable body odor produced by bacterial action on sweat from apocrine glands.
• Merocrine (eccrine) sweat glands are the most numerous skin glands there are about 3 to 4 million in adult skin and it is especially dense on palms, soles, and forehead. It is simple tubular glands. The watery perspiration helps cool the body.
• Myoepithelial cells contract in response to stimulation by the sympathetic nervous system and squeeze perspiration up the duct. They are found in both apocrine and merocrine glands.
• Sweat comes from blood plasma secreted by sweat glands. It's mostly water (99%), with a pH of 4-6, and contains solutes like sodium chloride. It can excrete drugs and inhibit bacterial growth with its acid mantle. Insensible perspiration is 500 mL/day, not visible on the skin. Diaphoresis is visible sweating. During exercise, up to 1 L of sweat can be lost per hour.
• Sebaceous glands are flask-shaped and have short ducts opening into hair follicles. It has a holocrine secretion style. Sebum is an oily secretion of sebaceous glands. It keeps skin and hair from becoming dry, brittle, and cracked. Lanolin is sheep sebum.
• Ceruminous glands are simple, coiled, tubular glands in the external ear canal. Their secretion combines with sebum and dead epithelial cells to form earwax (cerumen) which keeps the eardrum pliable, waterproofs the canal, kills bacteria, and makes guard hairs of the ear sticky to help block foreign particles from entering the auditory canal.
• Mammary glands are milk-producing glands that develop only during pregnancy and lactation. They are modified apocrine sweat glands and rich secretion is released through ducts opening at the nipple.
• With skin cancer, most cases are caused by UV rays of the sun damaging skin cell DNA. Most often on the head, neck, and hands. It is most common in fair-skinned people and the elderly. It is one of the most common, easily treated cancers. It also has one of the highest survival rates if detected and treated early.
• The three types of skin cancer are named for the epidermal cells in which they originate. Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.
• UV rays are not "tanning rays" or "burning rays". They don't cause a healthy tan but are thought to cause skin cancer. Sunscreens can prevent sunburn, but may not protect against cancer, especially with high SPF. Chemicals in sunscreen can also damage DNA and generate harmful free radicals.
• Basal cell carcinoma is the most common type of skin cancer. It is the least dangerous because it seldom metastasizes. It forms from cells in the stratum basale. The lesion is a small, shiny bump with a central depression and beaded edges.
• Squamous cell carcinoma arises from keratinocytes of the stratum spinosum. Lesions are usually on the scalp, ears, lower lip, or back of the hand. They have a raised, reddened, scaly appearance later forming a concave ulcer. The chance of recovery is good with early detection and surgical removal. It tends to metastasize to lymph nodes and may become lethal.
• Malignant melanoma is a skin cancer that arises from melanocytes. It is less than 5% of skin cancers but is the most deadly form. It can be successfully removed if caught early, but if it metastasizes it is usually fatal. The greatest risk factor is a familial history of malignant melanoma. The highest incidence is in men, redheads, and people who had severe sunburn as a child.
• Burns are the leading cause of accidental death. Deaths result primarily from fluid loss, infection, and toxic effects of eschar (burned, dead tissue). Debridement is the removal of eschar.
• Burns are classified into three types. First-degree burns only affect the top layer of skin, can appear reddish with slight edema and pain, but heal within a few days. Second-degree burns affect the second layer of skin, appear blistered and painful, and can take several weeks to heal, often leaving scars. Third-degree burns are the most severe and require skin grafts, infection control, fluid replacement, and nutritional support.
• Skin graft options include: Autograft which is tissue taken from another location on the same person’s body. Split-skin graft is a type of autograft and it means taking the epidermis and part of the dermis from an undamaged area such as the thigh or buttocks and grafting it into the burned area. Isograft means taking skin from an identical twin.
• Temporary grafts are used and discarded immediately because of immune system rejection. Homograft (allograft) is skin taken from an unrelated person. Heterograft (xenograft) is skin taken from another species. Amnion from afterbirth and Artificial skin from silicone and collagen.