Transcript Document
Integumentary System • Sites used • http://www.meddean.luc.edu/lumen/MedEd/medicine/dermatology/melton/skinlsn/sknls n.htm http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Integumentary/Integum.htm Skin • ~9 lbs. (4.1 kgs) • Covers S.A. of 15-20 ft2 (1.4 to 1.9 m2) • Every square inch contains 15’ blood vessels, 12’ nerves, 650 sweat glands, 100 oil glands, 1500 sensory receptors, & 3 million cells • Thickness varies from 1/32” to 1/8” • Skin cells die & replaced continuously • 3 layers = epidermis, dermis & hypodermis Skin-Major Functions • Protects • Excretion/Secretion • Helps regulate body temperature • Sensation (Cutaneous sensation) • Promotes vitamin D synthesis • Acts as reservoir for blood Protects • 3 ways • Chemically • Physically • Biologically Protects-Chemically • Acidic skin secretions inhibit bacteria from multiplying • Substances in sebum (oil) kill some bacteria • Melanin-shield skin from UV rays Protects-Physically • Keratinized cellsex.epidermis, hair and nails •Barrier to invading organisms Protects-Biologically • Dermal macrophages-2ndline of defense against bacteria • Epidermis contains macrophage like Langerhan’s cells = immunity Excrete/Secrete • Sweat-nitrogenous waste, sodium chloride • Sebum-secreted by sebaceous glands Regulate Body Temp. • Evaporation of sweat • Dermal blood vessels dilate and constrict Cutaneous Sensation • Sensory receptors-Meissner’s, Pacinian, Ruffini’s, Krauses, free nerve endings Vitamin D Synthesis. • Exposed to UV-skin converts cholesteral molecules to Vitamin D Reservoir for blood • Shunted from skin to general circulation ex. To working muscles Skin •3 layers •Epidermis •Dermis •Hypodermis 1. Epidermis • Most superficial layer of skin • First barrier of protection • Principle (main) cell type in epidermis = keratinocytes • 4-5 layers • 4 types of epidermal cells 2. Dermis • Contains sebaceous and sweat glands • Sensors: 2-A) Pacinian corpuscle – heavy touch & vibratiions 2-B) Meissner’s corpuscle – light touch 3. Hypodermis • Most of the blood flow (arteries & veins) • Contains fat for insulation & cushioning 4. Hairs • Protection • Decrease heat loss • Errector pilius – pulls hair errect during stress Common Disorders: 1. 2. 3. 4. Eczema Psoriasis Freckles/Moles Athelete’s Foot/Jock Itch 5. Melanoma 1. Calluses/Corns 2. Bruising 3. Impetigo Epidermal Cells • Keratinocytes: compose most of epidermis; make protein keratin • Keratin: waterproofs and protects skin • Melanocytes:synthesize melanin • Melanin protects against UV damage • Merkel cells: associated with sensory receptors (touch) • Langerhan’s cells: macrophages used in defense against microorganisms