The Infamous Integumentary System An insight to your skin, hair, nail, and glands.

Fast Facts & Functions Largest organ in body Most visible organ of the body Skin Hair Nails Glands Protection Maintain body temperature Stores nutrients (fat) Senses (touch, pain…) Excretion (of salts and water) Secretion (oil, waste, milk) Glands: sweat and sebaceous Protection of tissues and organs underneath; from impact, chemicals, and infections

The layers and parts Epidermis Dermis Subcutaneous layers Accessory structures Epidermis: stems cells attached to basement membrane; projections from underlying CT feed the epidermis; melanocytes are located in the bottom part of epidermis (brown-yellow, brown, and black pigment); these cells respond to sunlight; color “bubbles up; another pigment, carotene, also determines skin color, as well as dermal circulation (dilation of blood vessels) Dermis: papillary layer is made of LCT and has capillaries; Reticular layer is made of dence, irregular CT Subcutaneous layer: made of LCT and fat cells; some fibers from here attach to dermis Accessory structure: hair, sebaceous glands, sweat glands, and nails

The outer, epidermis, layer Stratified squamous epithelia This epithelia is divided into 5 layers: Stratum germinativum Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum Normally takes 2-4 weeks for cells to move from the bottom to the top SG: deepest layer attached to bm; stem cells and melanocytes lie here SS: very thick layers of cells, connected by desomozone, cells dividing SGr: cells stop dividing; cytoplasm from the dying cells start to make proteins and enyzmes SL: cells are flattened and packed well; enzymes create the protein, Keratin; cells shed or are washed away SC: superficial layer of dead epithelia cells and lots of keratin Psoriasis: cells divided very fast so epidermal layer sis replaces every week instead of every 2-4 weeks

The middle and inner The middle: Dermis Papillary layer Reticular layer The inner: Subcutaneous Layer Connective tissue fibers Loose connective tissues and fat cells Papillary: made of LCT, contains capillaries and nerves, nourished epidermi Reticular: mesh of DCT that supports and provides some flexibility Subcutaneous: children have a layer of body fat all over; this diminishes with growth and changes depending on sex (men: back, neck, upper arms, women: buttocks , hip, breasts); both can get “potbellies”

The Accessory Organs Hair Sebaceous glands Sweat glands Nails Originate in dermis and subcutaneous layer Keratinization occurs Arrector pili: goose bumps Sebaceous glands Oil, waxy substance, fats = sebum Sweat glands Discharge sticky substance; it smells when bacteria breaks it down Release sweat to cool body Nails Made of many dead keratin cells Hair: shaft from skin in dead, keratinized cells; color determined by melanocytes (turns grey as these cells make less melanin) Sebaceous glands: arrector pili muscles contract, squeezing waxy stuff onto skin surface; acne can occur with large sebaceous glands that become blocked, allowing bacteria to infect Sweat glands: bacteria break down, making smell; different type of sweat glands (over 3 mill) use their secretions to cool the body Nails: underlying blood vessels give nail pink color

The Epidermis http://www.udel.edu/biology/Wags/histopage/colorpage/cin/cintsm.GIF

The sebaceous gland http://www.udel.edu/biology/Wags/histopage/colorpage/cin/cintsm.GIF

Thick skin melanin http://www.udel.edu/biology/Wags/histopage/colorpage/cin/cintsm.GIF