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# Integumentary System * **Skin + Accessory Organs (hair, nails, glands):** * Largest and heaviest organ * Highly vulnerable to outside forces * Receives most medical attention * Exposed to radiation, trauma, infection, & chemicals. ## Layers of the Skin: 1. **Epidermis...

# Integumentary System * **Skin + Accessory Organs (hair, nails, glands):** * Largest and heaviest organ * Highly vulnerable to outside forces * Receives most medical attention * Exposed to radiation, trauma, infection, & chemicals. ## Layers of the Skin: 1. **Epidermis:** Stratified squamous epithelium (avascular) 2. **Dermis:** Deeper connective tissue layer (vascular) 3. **Hypodermis:** Connective tissue layer below dermis (not part of the skin but associated with it) ## Functions: * **Resistance to trauma and infection:** * Keratin (tough protection) * Dermcidin + defensins (natural antibiotics released by sweat glands, prevent overcolonization by microbes) * **Other Barrier Functions:** * Water retention; keratin & glycolipids help reduce water loss * UV radiation protection * Protection from harmful chemicals * **Vitamin D synthesis:** (in presence of UV light) * **Sensory Functions:** Receptors for temperature, touch, pain, and others. * **Thermoregulation:** * (when hot) vasodilation/vasconstriction, perspiration. * **Nonverbal Communication:** (facial expressions)