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This article provides an overview of the functions and facts about the integumentary system, including the three layers of skin, skin glands, epidermal appendages, wound healing, burns, and skin cancer. It also discusses common skin pathologies such as athlete's foot, cold sores, acne, impetigo, and warts.
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Functions of the Integument • Protection • Excretion • Sensory • Water balance • Thermoregulation • Endocrine (Vitamin D)
Some facts about skin • Largest organ of the Body • Approximately 2 square meters or 22 square feet • About 5 kg (11 pounds) • Ranges in thickness between 0.5 mm (genitals, lips, eyelids) to 5 or 6 mm on the soles of the feet. • Three layers, from superficial to deep: • Epidermis - outer layer of dead, keratinized cells • Dermis - dense irreg. c.t., nerves, vessels, etc. • Hypodermis - mostly subcutaneous adipose tissue
Skin: Thick Stratum granulosum Stratum corneum Stratum spinosum Stratum Basale Dermis
Thin skin: scalp Human scalp
Scalp: deep Human scalp
Skin Glands • There are two general types of skin glands: • Sudoriferous glands (sweat glands). • Eccrine glands - produce watery sweat for cooling, waste metabolite excretion & electrolyte excretion. Found all over the body except nail beds, genitals, & ear drums. Most dense on palms, soles, forehead & chest. • Apocrine glands - produce “stinky” sweat. Secrete a thicker, protein and lipid rich fluid and “pheromones”. Concentrated in arm pits, pubic region, areolae. Activated by the stress response or sexual arousal (sympathetic n.s.)
Skin Glands b. • Mammary glands - Mammary glands are specialized sudoriferous glands. They produce milk. And yes, men have them too! • Ceruminous glands - Modified sweat glands that line the external auditory canal. They make “cerumen”, also known as ear wax. 2. Sebaceous glands - produce oily secretion called “sebum”. These glands open onto the hair follicles and the oil keeps hair supple and skin water resistant..
Connective tissue Root sheath Follicle wall Hair follicle: cross section Internal root sheath Cuticle Cortex Medulla Hair follicle in cross section
Wound healing PMN = Polymorphonuclear leukocyte
Stages of wound healing • Inflammatory • Migratory • Granulation • Maturation • Fibrosis: scar tissue formation • Hypertrophic scar is one that remains within the boundaries of the original wound. • Keloid scar is one that extends to surrounding tissue beyond the original wound.
Skin Cancer • Basal cell carcinoma - 75%, arise from epidermal cells. Rarely metastasize to other tissues. Easily removed. • Squamous cell carcinoma - around 20%, may or may not metastasize. Also from epidermal tissue. • Malignant melanoma - remaining 5%, arise from melanocytes. Often delayed reaction to sun exposure by 10 - 20 years. Poor prognosis, they metastasize very rapidly once they begin to grow.
Risk factors for skin cancer • Skin type - lighter skin pigmentation = higher risk • Sun exposure - lower latitude, more direct sun. Longer time, greater exposure. • Family history - Genetics nearly always plays at least some role in susceptibility to disease. • Age - older = longer exposure. • Immune system health - people with compromised immune systems are at greater risk.
Other skin pathologies • Athlete’s foot - caused by a fungus • Cold sore - herpes simplex virus type I. HSV II causes genital herpes. • Acne - inflamed sebaceous glands. Can be seriously disfiguring. Accutane™ and Retin-A™ are prescription treatments which are derived from vitamin A and have proven helpful in severe cases. OTC treatments include salicylic acid and benzoyl peroxide with variable efficacy. • Impetigo - superficial infection caused by staphylcocci or streptococci, two genera of bacteria very common to skin. • Warts - raised lesions caused by papilloma virus. HPV causes genital warts, a sexually transmitted infection, that is often associated with cervical cancer in women.
