The Integumentary System: Skin

Integumentary System The Body Covering (Fun Fact! Largest organ of the body) Includes: Skin, Nails & Hairs Skin A.K.A. Cutaneous Membrane Functions: Body Temperature Regulation: Sweating at surface and adjusting blood flow in dermis. Protection: Keratin protects from microbes, abrasions, heat and chemicals, lipids slow evaporation of water, melanin protects from UV rays. Cutaneous Sensations: Sensory input/output Excretion and Absorption: Eliminates substances, passage of materials into body cells (drugs) Synthesis of Vitamin D: UV light activates creation of Vit D

Structure Skin is divided into two main parts: Epidermis (epi = above) Surface epithelial layer Dermis: Deeper connective tissue layer Subcutaneous Layer Deep dermis not part of the skin. Fibers from dermis anchor skin to this layer which then allows for attachment to other tissue and/or organs. Structure

Epidermis Made of keratinized stratified squamous epithelium Capable of regeneration (new cells ~ q4 weeks) 4 cell types: Keratinocytes: 90% of epidermal cells, 4 – 5 layers, produces keratin (rough fibrous protein that protects skin), waterproofs skin. Melanocytes: 8% of epidermal cells, produce the pigment melanin, transfer melanin to keratinocytes, susceptible to UV light damage. Langerhans cells: Produce immune response against pathogens entering skin. Merkel cells: Detect touch/sensory sensations.

Dermis Consists of two distinct regions: The superficial part is composed of areolar connective tissue. The deeper part is composed of dense irregular connective tissue. Attaches to the subcutaneous layer. The outer layer contains nerve endings for touch, thermal sensations, pain, tickling, and itching.

Skin Color Skin color is due to the melanin in the epidermis, carotene in the dermis, and hemoglobin in the capillaries of the dermis. Melanin (Brown-Black pigment) Darkness depends on amount of melanin produced. Gives some protection against UV Malignant melanoma, (cancer of the melanocytes), is a particularly serious skin cancer. Liver or age spots, are non-cancerous clusters of melanin. Carotene (Yellow-Orange pigment) In deeper skin and adipose layers Hemoglobin (Pink-Red pigment) Found in blood Depends on blood flow

Review: Skin What are the 5 functions of skin? What are the two main parts of skin called? What 4 cells make up the superficial/thinner part of the skin? What is the function of the subcutaneous layer? What specific type of epithelial cells make up the epidermis? Which skin layer contains nerve endings? Which pigments contribute to which skin color? The shade of your skin depends on which factors? What are the characteristics and functions of keratinocytes?

The Integumentary System: Accessory Structures of the Skin

Hair Function: Protection Found: On most skin surfaces Composition: Not on palmar surfaces of hand and fingers or plantar surfaces of feet Composition: Keratinized cells Shaft: Mostly above ground Root: Below surface Surrounded by hair follicle Bulb: Base of hair follicle includes matrix producing cells and blood vessels. Nerves: Hair root plexuses Sensitive to touch Muscle (Smooth): Arrector pili Contraction causes goose bumps Hair Hair Shaft Sebaceous Gland Hair Root Hair Root Plexus Arrector pili muscle Bulb Apocrine sweat gland

Glands Sebaceous Glands: Secrete oily sebum Protects skin from drying out and bacteria Connected to hair follicles Sudoriferous (soo-dor-IF-er-us) Glands: Secrete sweat Eccrine are widely distributed, & aid in thermoregulation Apocrine are found in the axilla, groin, areolae, beard Ceruminous (se-ROO-mi-nus) Glands: Secrete wax External auditory canal Combine with sebum to produce earwax Provide barrier against foreign bodies Glands

Nails Function: Help us grasp, manipulate objects, protect ends of digits, scratching Composition: Plates of packed keratinized cells of the epidermis. Nail body: Visible portion Free edge: Part extending past digit Root: Part not visible Growth: 1 mm per WEEK! Slows within 2nd / 3rd decade Becomes brittle with age Free Edge Nail Body Root

Review: Accessories What are the 5 functions of hair? What protein is hair composed of? What 5 structures make up hair within skin? What causes goose bumps? What is sebum? Which gland secretes sebum? Which gland aids in thermoregulation? How? Which glad’s secretions combine with sebum to produce earwax? Why is this important? What are the functions of nails? What specifically are nails made of? Of the 5 nail parts, name 3?