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The Integtumentary System. 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)
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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
Organization of the Epidermis Figure 5–2
Melanocytes Figure 5–5
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..
Sebaceous Glands Figure 5–10
Apocrine Sweat Gland Figure 5–11a
Other Integumentary Glands • Mammary glands: • produce milk • Ceruminous glands: • protect the eardrum • produce cerumen (earwax)
Control of Glands • Autonomic nervous system: • controls sebaceous and apocrine sweat glands • works simultaneously over entire body • Merocrine sweat glands: • are controlled independently • sweating occurs locally
Structure of a Hair Figure 5–9d
Connective tissue Root sheath Follicle wall Hair follicle: cross section Internal root sheath Cuticle Cortex Medulla Hair follicle in cross section
Structures of a Follicle Figure 5–9c
Ridges and Ducts Figure 5–4
Repair of Localized Injuries to the Skin: Step 1 • Bleeding occurs • Mast cells trigger inflammatory response
Repair of Localized Injuries to the Skin: Step 2 • A scab stabilizes and protects the area
The Inflammatory Response • Germinative cells migrate around the wound • Macrophages clean the area • Fibroblasts and endothelial cells move in, producing granulation tissue
Repair of Localized Injuries to the Skin: Step 3 • Fibroblasts produce scar tissue • Inflammation decreases, clot disintegrates
Repair of Localized Injuries to the Skin: Step 4 • Fibroblasts strengthen scar tissue • A raised keloid forms
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.
Rule of Nines • To estimate burn damage, surface area is divided into multiples of 9 Figure 5–14
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.
Skin Cancer Figure 5–6
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.
Effects of Aging • Epidermal thinning • Decreased numbers of Langerhans cells • Decreased vitamin D3 production • Decreased melanocyte activity • Decreased glandular activity (sweat and oil glands)
Effects of Aging • Reduced blood supply • Decreased function of hair follicles • Reduction of elastic fibers • Decreased hormone levels • Slower repair rate