Summary Skin Physiology Revised

Skin as an organizing model What is it? (Anatomy) What is it made of? (Histology) What does it do? (Physiology)

What is it (anatomy)? Outer covering of body Keratinized Hair—head, pubic regions Nails—fingers, toes Divided into segments called

dermatomes (“Zebra-man”)

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What does it do? • PROTECTION – Air = desiccation – Water = bloating/”pruning” – Sun/u-v = burns – Cold/heat = frostbite/heat stroke/thermoregulation • STRUCTURAL – Integrity of body – Muscle attachment 04/10/09

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How does it do it? PROTECTION (mostly epidermis) Desiccation—keratin, lipid layer Water = keratin, lipid layer Sun/u-v = role of pigment/melanin Cold/heat = surface blood vessels

STRUCTURAL (mostly dermis) Integrity—Dermal layer has network of tough

collagen fibers in connective tissue Sub-dermal layer where muscle tendons insert 4

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SKIN FUNCTION  Serves as a barrier to physical, biological, and

chemical agents and to radiation  Regulates body temperature (thermoregulation) by evaporative cooling (perspiration), heat radiation at the surface of the body (blood circulation), and   serves as insulation (a minor function in humans)  Site of excretion through sweat glands  Photochemical production of vitamin D  Serves as a sensory organ

What is it made of? (histology—study of tissues) Layers of skin are

two fundamental types of tissue organization Epidermis =

epithelium Dermis = connective tissue 6

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Epidermis—a stratified epithelium

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Dermis—connective tissue substrate

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Skin is really an organ… Made up of two very different

basic tissue types the epidermis which is composed of epithelial tissues The dermis which is composed of connective tissue

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