Copyright 2010, John Wiley & Sons, Inc. Chapter 5 The Integumentary System

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Copyright 2010, John Wiley & Sons, Inc. Integumentary System The body’s covering Includes: skin, nails, and hairs Skin: cutaneous membrane

Copyright 2010, John Wiley & Sons, Inc. Structure Two main parts  Epidermis - surface epithelial layer  Dermis - deeper connective tissue layer Subcutaneous (subQ) layer or hypodermis lies deep to dermis; is not part of the skin

Copyright 2010, John Wiley & Sons, Inc. Integumentary System

Copyright 2010, John Wiley & Sons, Inc. Epidermis Keratinized stratified squamous epithelium Cell types (4):  Keratinocytes  Melanocytes  Langerhans cells  Merkel cells

Copyright 2010, John Wiley & Sons, Inc. Epidermal Cells Keratinocytes  90% of epidermal cells  4-5 layers  Produce keratin  Protects skin  Waterproofs skin

Copyright 2010, John Wiley & Sons, Inc. Epidermal Cells Melanocytes  Produce melanin that gives color to skin, hairs  Transfer pigment to keratinocytes  Make up 8% of epidermal cells

Copyright 2010, John Wiley & Sons, Inc. Epidermal Cells Langerhans cells  Immune response Merkel cells  Sense of touch  Consist of tactile disc and neuron for touch sensation

Copyright 2010, John Wiley & Sons, Inc. Epidermal Layers Four Layers (strata)  Stratum basale Includes stem cells; new cells arise here  Stratum spinosum: 8-10 cell layer Cells beginning to look flattened  Stratum granulosum makes keratin Losing cell organelles and nuclei Have waterproofing lipid  Stratum corneum: flattened dead cells Cells here consist mostly of keratin. Cells here are shed and replaced from below.

Copyright 2010, John Wiley & Sons, Inc. Skin Color Melanin: dark color  Darkness depends on amount of melanin produced.  Provides some protection against UV rays Carotene: yellow orange  In stratum corneum and adipose layers- Hemoglobin in blood: pink-red  Depends on blood flow

Copyright 2010, John Wiley & Sons, Inc. Accessory Structures Hair Skin glands Nails

Copyright 2010, John Wiley & Sons, Inc. Hair Found on most skin surfaces  Not on palmar surfaces of hand and fingers or plantar surfaces of feet Made of fused keratinized cells Consists of shaft and root Surrounded by hair follicle  Base is bulb which includes growing matrix producing cells Nerves in hair root plexuses Muscle that pulls on hair: arrector pili Causes hair to stand on end

Copyright 2010, John Wiley & Sons, Inc. Hair

Copyright 2010, John Wiley & Sons, Inc. Glands Sebaceous gland: secrete oily sebum  Connected to hair follicles; keeps hair from drying out Sudoriferous (sweat) gland  Eccrine sweat gland  Wide distribution- thermoregulation  Apocrine sweat gland  Axilla, groin, areolae, beard  Contain other cell material Ceruminous (wax) gland  Wax combines with sebum to produce earwax

Copyright 2010, John Wiley & Sons, Inc. Nails Plates of packed hard dead keratinized cells Nail body: major visible portion Free edge: part extending past finger or toe Root: cells deep to here (in nail matrix) form new nail cells

Copyright 2010, John Wiley & Sons, Inc. Nails

Copyright 2010, John Wiley & Sons, Inc. Nails

Copyright 2010, John Wiley & Sons, Inc. Functions Temperature regulation Protection Sensory reception Excretion and absorption: small amounts Vitamin D synthesis

Copyright 2010, John Wiley & Sons, Inc. Aging Adolescence: can develop acne Most effects in dermis, with visible signs of aging by about age 40. These include:  Loss of collagen fibers  Loss of elasticity  Loss of immune responses  Decreased melanocyte functions: gray hair, skin blotches  Thinning of skin and hairs Anti-aging treatments