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