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The Integumentary System Amanda Dunne The Integumentary System The primary functions Storage (Water, Fat, Vitamin D) Regulation of body temperature Prevention of dehydration (water loss) Layers: Epidermis (superficial) Dermis (deep) Hypodermis (Subcutaneous) Structure of human skin Epidermis Thinnest most superficial layer Critical barrier against the outside world Consists of several layers of varying thickness This layer determines the thickness or thinness of the skin. Can you guess where the thickest and thinnest layers might be? What does the epidermis contain? Keratinocytes Keratin producing cell with gives skin its protective properties Melanocytes Pigment (Melanin) producing cell which gives skin its colour Langerhans cells Immune cells Merkel cells Sensory nerve cells providing sensation for touch Layers of the epidermis The epidermis consists of five sub-layers that work together to continually rebuild the surface of the skin Stratum corneum Lucid layer Granular layer Squamous cell layer Basal cell layer 1. Basal cell layer Deepest layer which contains young keratinocytes Also called germinative layer because these cells are constantly dividing. This pushes the older cells to the surface. Contains melanocytes which secrete melanin which protect this deep layer from sunlight. 2. Squamous cell layer This layer is the thickest. Sometimes known as the ‘prickly layer’ because It contains keratinocytes which appear irregular and spiny. Keratinocytes = Keratin, a tough protective protein Langerhans cells which alert the immune system when skin gets damaged 3. Granular layer Granular layer containing flattened cells Pushed upwards towards the surface Eventually dehydrate and die 4. Lucid layer Clear lucid layer Pushed upwards towards the surface Eventually dehydrate and die Very thin transparent layer 5. Stratum corneum The outermost (most superficial) layer made up of 10-30 layers that are continually shedding Also called ‘horny layer’ because it toughness resembles animals horns This layers is continually sloughed off and new cells push up from underneath Epidermal Cell turnover Complete cell turnover every 28-30 days in adults. In elderly adults the same process can take between 45-50 days. The Dermis Located underneath the epidermis, the main functions of the dermis are to: Regulate body temperature Supply the epidermis with nutrient saturated blood. The Dermis Binds the entire body together like a body stocking Makes up 90% of skin thickness Stores most of the body’s water supply Rich supply of nerve fibres, blood and lymph vessels The blood vessels supply nutrients and oxygen to the skin and take away cell waste. The blood vessels transport the vitamin D produced in the skin back to the rest of the body. Contains most of the skin specialised cells and structures. Sebaceous glands Sebaceous glands secrete oil that helps keep the skin smooth, supple and waterproof. Protects against bacterial or fungal overgrowth on skin. Sebaceous, or oil secreting glands, are attached to hair follicles and can be found almost everywhere on the body. Hair Follicles The hair follicle is a tube-shaped sheath that surrounds the part of the hair that is under the skin and nourishes the hair Hair follicle Sweat Glands The average person has about 3 million sweat glands. Two types: Eccrine glands - true sweat glands. Found over entire body, they regulate body temperature by bringing water via the pores to the surface of the skin, where it evaporates and reduces skin temperature. •Apocrine glands specialised and found only in the armpits and pubic region. Secrete a milky sweat that encourages the growth of the bacteria responsible for body odour. Nerve Endings The dermis layer also contains pain and touch receptors that transmit sensations of pain, itch, pressure and information regarding temperature to the brain for interpretation. If necessary, shivering (involuntary contraction and relaxation of muscles) is triggered, generating body heat. Sensory Receptors of the skin: The Hypodermis Also known as the subcutaneous layer The innermost layer of the skin Consists of a network of fat and collagen cells. Functions as an insulator, conserving the body's heat, and as a shock-absorber, protecting the inner organs.