Chapter 5

The Integumentary SystemRelated topics

Dermatology, acne, tanning, aging, balding, tattooing, skin cancer, massage, appearance, smell, etc.

Layers of Skin

• Epidermis – stratified squamous keratinized epithelium

• Dermis – connective tissue

• (Hypodermis – CT)

(5.1)

Functions of Skin• Protection

– Cushioning– Insulation (hot – cold)– Barrier to chemicals, infectious agents, toxins– Waterproof covering – dehydration

• Temperature Regulation– Capillaries & sweat glands

• Excretion– Sweat glands

• Block UV rays• Synthesize vitamin D• Sensory Receptors

Epidermis• Keratinocytes • Connected by

desmosomes• Continuous turnover

(35-45 days)• Mitosis at basement

membrane• Superficial

keratinized layer• Free nerve endings

5.3b

Epidermis• Thick skin

– Palms & soles– Thick superficial layer

• Thin skin– Everywhere else

5.4ab

Stratum Basale

• Keratinocyte stem cells (mitotic)

• One cell layer• Melanocytes

produce melanin and transfer to keratinocytes– Stimulated by UV

5.3b

Stratum Spinosum

• Keratinocytes attached by desmosomes (why?)

• Many cell layers• Why is it called

“spiny”?

5.3b

Stratum Granulosum

• Keratinocytes with keratohyalin granules

5.3b

Stratum Corneum

• Dead keratinocytes (plasma membrane + keratin)

5.3b

Dermis Components

• CT cells: fibroblasts, macrophages, mast cells, wbcs

• Fibers: collagen, elastic, reticular

• Nerves & blood vessels

• Skin derivatives (5.1)

Papillary Layer

• Superficial 20%• Areolar CT• Dermal papillae• Capillary beds• Sensory nerve

endings

(5.1)

Reticular Layer

• Deep 80%• Dense irregular CT• Location of:

– Sensory receptors– Sweat glands &

ducts– Hair follicles & roots– Blood vessels– Arrector pili muscles

(5.1)

Hypodermis

• (aka superficial fascia, subcutaneous layer)

• Underneath skin• Adipose and areolar

CT• Attached to muscle• Insulates

(5.1)

Skin Color

• Melanin pigment– From

melanocytes– To

keratinocytes– Variations

• Yellow-red-brown-black 5.3b

Skin Color

• Carotene– From plant foods

• vegetables (such as carrots, tomatoes, kale, spinach, winter squashes, broccoli and romaine lettuce) and fruits (including apricots, tangerines, watermelon, cantaloupe and grapefruit).

– Yellow-orange• excess carotene accumulates over a

period of weeks in the skin, primarily on the palms of hands and feet, lending a yellow-orange hue

Can your skin turn orange if you eat too many carrots? We plan to answer that question as I go on a

carrot diet for thirty days.

www.steelgirl.com/carrot3.htm

Skin Color

• Hemoglobin– Oxygenated Hb in dermis– Red– Cyanosis – blue color of poorly

oxygenated Hb

Cyanosis

http://www.lf2.cuni.cz/Projekty/interna/foto/014/pic00011.jpg

Hair

• Shaft and root• Keratinized cells• Function: light

touch• Pigment

transferred from melanocytes

(5.1)

Hair Follicle

• Extension of epidermis around hair root

• Located in dermis• Root hair plexus• Hair bulb• Arrector pili muscle

5.5c

Sebaceous Glands• Simple alveolar

gland• Duct to hair

follicle• Sebum – lipid

secretion• Holocrine

secretion – cell fragments

(5.1)

Sweat Glands

• Simple tubular gland• Water, salts, wastes• Cools body surface• Eccrine sweat glands

– All over body surface

• Apocrine sweat glands– Axilla, anus, genitals– 2° sex characteristics– BO/deodorant

(5.1)

Skin Cancer

• Basal cell carcinoma – least malignant, most common

• Squamous cell carcinoma – keratinocytes in stratum spinosum

• Melanoma – metastasize rapidly

http://www.pueblo.gsa.gov/cic_text/health/skin-cancer/skin2a.gif

http://www.mskcc.org/mskcc/shared/graphics/melanoma.jpg