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Hole’s Human Anatomy and Physiology

Eleventh Edition

Shier w Butler w Lewis

Chapter 6

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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•Referred to as “Cutaneous Membrane” •Composed of several tissues including:

Stratified squamous epithelium Glandular epithelium Dense irregular CT Smooth muscle Adipose Nervous tissue

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1. Protection 2. Excretion 3. Regulates body temperature 4. Sensory reception 5. Contains immune system cells 6. Synthesizes Vitamin D 7. Acts as a blood reservoir

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•Physical Barrier •From water loss •From injury •From chemicals and microorganism

•Chemical Barrier

•pH of 5-6 •Prevents microorganism growth

•Biological Barrier •Langerhan’s cells (epidermis) •Macrophages and mast cells (dermis)

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Minimal amounts of urea and uric acid are excreted through the skin via sweat.

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Uses negative-feedback mechanism. See Figure 6.11 on page 183

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Hyperthermia – abnormally high body temperature

Hypothermia – abnormally low body temperature

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•Light touch detection = Meissner’s corpuscles

•Located in dermal papillae •Concentrated in areas such as fingertips, palms, soles, eyelids, tip of tongue, genitalia

•Pressure detection = Pacinian corpuscles •Located in deep dermis and subcutaneous regions

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•UV rays in sunlight activate Vitamin D synthesis

•Vitamin D needed for normal bone and tooth development •

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• Dermis houses about 10% of the body’s blood vessels

•Skin only requires 1-2% of the body’s blood

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Some cells (keratinocytes) produce substances that simulate development of some WBCs

•Langerhan’s and macrophages •Interact with T-helper cells

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•2 Layers •Epidermis • Dermis

• Subcutaneous layer beneath dermis NOT part of skin

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• AKA - hypodermis

• Composed of •loose connective tissue •adipose tissue

• Insulates

• Contains major blood vessels

http://www.youtube.com/watch?v=M7qirJXWhzc&feature=related

http://vimeo.com/9143114

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Epidermolysis Bullosa, or EB, is a rare genetic skin disorder the the majority of people have never heard of, yet it affects 100,000 children across the United States. Children born with this disease lack the ability to produce the collagen-7 protein that acts as a glue to bind the inner and out layers of skin together.

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• lacks blood vessels

• keratinized stratified squamous epithelium

• thickest on palms and soles (0.8-1.4mm) • melanocytes provide melanin • rests on basement membrane

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1. stratum corneum – outermost, composed of dead keratinized cells

2. stratum lucidum – extra layer only found in thick skin of soles and palms

3. stratum granulosum – 3-5 layers of flattened cells with keratin granules

4. stratum spinosum – many layers of spiky cells with large nuclei

5. stratum basale – innermost layer, single layer of mitosing cuboidal epithelium, containing melanocytes

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• Functions: 1. binds epidermis to

underlying tissues 2. Nourishment of

epidermis

• on average 1-2 mm thick

• Contains : •Muscle cells •Sensory receptors •Blood vessels •Hair follicles •Glands

Papillary layer – (20%)

Composed of loose CT

Papillae (finger-like

projections) form

fingerprints

Meissner corpuscles

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Reticular layer – (80%)

Composed of dense CT

Bundles of collagen,

elastic, and reticular

fibers give skin its

strength & resiliency

Pacinian corpuscles

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Hair Follicles

Nails

Sebaceous Glands (Oil)

Sudoriferous Glands (Sweat)

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• epidermal cells • tube-like depression • extends into dermis • hair root • hair shaft • hair papilla • dead epidermal cells • melanin • arrector pili muscle

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• protective coverings

• nail plate

• nail bed

• lunula

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• usually associated with •hair follicles

• holocrine glands

• secrete sebum

• absent on palms and soles

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• sudoriferous glands

• widespread in skin

• originates in deeper dermis or hypodermis

• eccrine glands

• apocrine glands

• ceruminous glands

• mammary glands

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Genetic Factors • varying amounts of melanin • varying size of melanin granules • albinos lack melanin

Environmental Factors • sunlight • UV light from sunlamps • X rays • darkens melanin

Physiological Factors • dilation of dermal blood vessels • constriction of dermal blood vessels • accumulation of carotene • jaundice

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• Skin becomes scaly • Age spots appear • Epidermis thins • Dermis becomes reduced • Loss of fat • Wrinkling • Sagging • Sebaceous glands secrete less oil

• Melanin production slows • Hair thins • Number of hair follicles decrease • Nail growth becomes impaired • Sensory receptors decline • Body temperature unable to be controlled • Diminished ability to activate Vitamin D

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Acne Vulgaris

•most common skin disorder •sebum and epithelial cells clog glands •produces whiteheads and blackheads (comedones) •anaerobic bacteria trigger inflammation (pimple) •largely hormonally induced •androgens stimulate sebum production •treatments include antibiotics, topical creams, birth control pills

Athlete’s Foot • Fungual infection

usually in the skin of the

toes and soles

Ringworm • Fungal infection on the

skin that creates a ring

like pattern

Both like moist environments and are spread by direct contact or contact with contaminated objects.

Birth mark (aka – “nevus”) • Over 80% of babies have one

• 2 types: vascular & pigmented

Vascular involves blood vessels in skin

Pigmented results from abnormal amounts of

pigments in skin

• Common types include café au lait spots, moles,

port-wine stains, Mongolian spots, and

hemangiomas

• Can but rarely cause severe disfigurement &

tumor growth

Boil vs Carbuncle • Boil in a bacterial infection of the skin,

produced when bacteria enter a hair follicle.

• Carbuncles are bacterial infections that have

spread to the subcutaneous tissues.

Eczema • Non-contagious skin rash, often

accompanied by itching, blistering, crusting, scaling, oozing and bleeding.

• Some types are an inherited condition

Psoriasis • Skin cells grow at an abnormally

high rate.

• Results in red patches with silvery scales

• Immune system related and can be inherited

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• 1st degree (superficial partial-thickness burn)

• Only epidermis is involved

• Edema (swelling), shedding of surface skin

• Area will appear red in color

• Heals without scaring

• 2nd degree ( deep partial-thickness burn)

Involves both epidermis and dermis

Fluid escapes from dermal capillaries and

collects in epidermal cells….thus blistering

occurs

May be red in color or waxy white

Usually heals without scaring

3rd degree (full-thickness burn)

• Destroys the epidermis, dermis, &

accessory structures of the skin

• Area will look leathery, and be red, black

or white in color

• Skin grafts are necessary for healing

(autograft or homograft)

• Scaring will occur

http://www.youtube.com/watch?v=eXO

_ApjKPaI&feature=player_embedded

Carcinomas • arise from epithelia cells

• squamous or basal types

• Usually treated by surgical removal

• Most common type of skin cancer

Melanomas

• arise from melanocytes

• Harder to treat

• On the rise in last 20 yrs b/c of tanning habits