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chapter 5

Skin (Integument = covering). Consists of three major regionsEpidermis

Rita
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chapter 5

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    1. Chapter 5 The Integumentary System

    2. Skin (Integument = covering) Consists of three major regions Epidermis—superficial region Dermis—middle region Hypodermis (superficial fascia)—deepest region Subcutaneous (sub Q) layer deep to skin (not technically part of skin) Mostly adipose tissue

    4. Epidermis Keratinized stratified squamous epithelium Cells of epidermis: Keratinocytes Melanocytes Epidermal dendritic (Langerhan’s) cells—macrophages that help activate immune system. Tactile (Merkel) cells

    5. Layers of the Epidermis: Stratum Basale (Basal Layer) Deepest epidermal layer firmly attached to the dermis Single row of stem cells Also called stratum germinativum: cells undergo rapid division (mitosis). Journey from basal layer to surface takes 25–45 days.

    6. Layers of the Epidermis: Stratum Spinosum (Prickly Layer) and Stratum Granulosum (Granular Layer) Keratinocytes becoming impregnated with keratin, glycolipids, and melanosomes. Stratum Lucidum (Clear Layer) Occurs only in thick skin

    7. Layers of the Epidermis: Stratum Corneum (Horny Layer) 20–30 rows of dead, flat, keratinized membranous sacs (cells) 75% of the epidermal thickness Functions:

    9. Dermis Strong, flexible connective tissue. Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells. Two layers: Papillary & Reticular

    11. Layers of the Dermis: Papillary layer Areolar connective tissue with collagen and elastic fibers and blood vessels and lymphatic vessels. Dermal papillae contain:

    12. Layers of the Dermis: Reticular layer ~80% of the thickness of dermis Collagen fibers provide strength and resiliency. Elastic fibers provide stretch-recoil properties. Pacinian corpuscles

    13. Skin Markings: Friction Ridges Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints.

    14. Skin Markings Cleavage Lines Collagen fibers arranged in bundles form cleavage (tension) lines. Incisions made parallel to cleavage lines heal more readily

    15. Skin Markings: Flexure lines occur near joints. Stretch marks are the result of dermal tearing as the skin is stretched beyond the max.

    16. Skin Color Three pigments contribute: Melanin – produced by melanocytes Yellow to reddish-brown to black, responsible for dark skin colors. Forms “pigment shields” for nuclei Freckles and pigmented moles = local accumulations of melanin Carotene – Hemoglobin -

    17. Appendages of the Skin Derived from epidermis Sweat glands Oil glands Hairs and hair follicles Nails

    18. Sweat Glands Two main types of sweat (sudoriferous) glands Eccrine (merocrine) sweat glands—abundant on palms, soles, and forehead

    20. Sweat Glands Apocrine sweat glands—confined to axillary and anogenital areas.

    21. Sweat Glands Specialized apocrine glands Ceruminous glands Mammary glands

    22. Sebaceous (Oil) Glands Widely distributed Most develop from hair follicles Become active at puberty Sebum Oily holocrine secretion Bactericidal secretions Softens hair and skin *Seborrhea

    24. Hair Functions Alerting the body to presence of insects on the skin . Guarding the scalp against physical trauma, heat loss, and sunlight. Distribution Entire surface except palms, soles, lips, nipples, and portions of external genitalia.

    25. Hair Visible portion consists of dead keratinized cells. Contains hard keratin; more durable than soft keratin of skin. Hair pigments: melanins (yellow, rust brown, black).

    27. Hair Follicle Extends from the epidermal surface into dermis Two-layered wall: Hair bulb: expanded deep end: Surrounded by nerve plexus. Hair papilla Epidermal cells produce hair matrix. Melanocytes

    29. Hair Follicle Arrector pili Sebaceous gland

    30. Types of Hair Vellus—pale, fine body hair of children and adult females Terminal—coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males)

    31. Types of Hair Hair Growth Cycles Growth phase varies (6–10 years in scalp, 3–4 months in eyebrows) Varies among body regions and age.

    32. Hair Thinning and Baldness Alopecia—hair thinning in both sexes after age 40. Alopecia areata – immune sytem attacks hair follicle. True (frank) baldness Genetically determined and sex-influenced condition. Male pattern baldness is caused by follicular response to DHT.

    33. Structure of a Nail Scale-like modification of the epidermis on the distal, dorsal surface of fingers and toes. Structure Matrix Body Free edge Eponychium = cuticle, Hyponychium = “quick”

    35. Functions of the Integumentary System Protection—three types of barriers Chemical Physical/mechanical barriers Biological barriers

    36. Functions of the Integumentary System Body temperature regulation ~500 ml/day of routine insensible perspiration (at normal body temperature) At elevated temperature, dilation of dermal vessels and increased sweat gland activity (sensible perspirations) cool the body

    37. Functions of the Integumentary System Cutaneous sensations Metabolic functions Synthesis of vitamin D precursor and collagenase Chemical conversion of some chemicals to carcinogens and some hormones to active form.

    38. Functions of the Integumentary System Blood reservoir—up to 5% of body’s blood volume Excretion—nitrogenous wastes (limited amount) and salt in sweat.

    39. Skin Cancer Causes: exposure to UV, frequent irritation, physical trauma causes damage to DNA. ?Remergent – cream that promotes DNA repair.

    40. Skin Cancer Basal cell carcinoma Occurs in stratum basale cells Least malignant, slow growing Red shiny bumps Rx – surgical removal

    41. Skin Cancer Sqamous cell carcinoma Keratinocytes from the stratum spinosum 2nd most common, grows rapidly. Red scaly patch. Rx – surgical removal, radiation.

    42. Skin Cancer Melanoma Involves melanocytes Highly metastatic and resistant to chemotherapy Treated by wide surgical excision accompanied by immunotherapy

    43. Skin Cancer ABCD (E) Rule Asymmetry Border Color Diameter Elevation

    44. Burns Caused by heat, radiation, chemicals, electricity.

    45. Burns 1st degree – epidermis only, heals quickly. 2nd degree – penetrated the upper dermal layer, blisters formed. 3rd degree – penetrates all layers of skin. There is no pain at first because nerve endings are damaged.

    46. Burns 3rd degree Immediate Threat – hypovolemic shock. Loss of fluids and proteins from exposed skin. Estimation of fluid loss using Rule of Nines for body surface area affected. Secondary threat – infection. Rx – IV fluids, increased calorie intake, artificial skin.

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