What is the integumentary system? Organ system that protects the body from damage Guards the body’s physical and biochemical integrity Functions: Waterproof, cushion, and protect deeper tissues, excrete waste, regulate body temperature, attachment point for sensory receptors, vitamin D synthesis
The Skin The skin is the body’s integumentary system Largest of the body’s organ systems 12% - 15% of body’s weight Is composed of a minimum of 3 layers: Epidermis Dermis Hypodermis
Epidermis Outermost layer composed of epithelial cells Composed of 4 layers: stratum basale, spinosum layer, stratum granulosum, stratum corneum Has no blood supply and depends on diffusion from dermal cells for metabolic needs
Stratum Basal Bottom most layer responsible for constantly renewing epidermal cells Contains one row of undifferentiated columnar stem cells that divide frequently Half of the divided cells move to the next layer to begin the maturing process Other half stays in basal layer and divides over and over to replenish basal layer Contains melanocytes: the cells responsible for creating melanin, the pigment responsible for skin color
Spinosum Layer Cells transferred here change from columnar to polygonal Cells begin to synthesize keratin Keratin is the key component in making up the outer layer of skin, along with hair and nails.
Stratum Granulosum Cells here have lost their nuclei and are characterized by dark clumps of cytoplasmic material Here keratin proteins and water-proofing lipids are produced and organized
Stratum Corneum Cells here known as coreocytes and have flattened out Cells here are composed of mainly keratin protein which add strength but also allow absorption of water Responsible for integrity and hydration of skin Disruptions in this layer can result in a variety of skin problems
Dermis 2 Layers Stratum papillare Stratum Reticulare Dermis layer responsible for: Cushioning body Sense of touch Made up of Collagen Elastic Fibers Hair Follicles
Stratum Papillare Makes up upper part of dermis It forms the sharp, wave shaped border of the dermis The wavy surface increases the contact with the epidermis Made of loose connective tissue Connects the dermis to the epidermis
Stratum reticulare Makes up a lower part of the dermis Much thicker then the papillary The protein fibers give the layer Strength Extensibility Elasticity Contains Roots of hair, sebaceous glands, sweat glands, receptors, nails, and blood vessels
Hypodermis Sometimes referred to as the Subcutaneous layer and the superficial fascia The lowermost layer of the integumentary system It contains larger blood vessels and nerves than those in the dermis A major storage site for adipose tissue
Contents of The Hypodermis Cells Fibroblasts Adipose Macrophages Subcutaneous Fat Layer of insulation to hold in heat Assists in Homeostasis
Accessory Structures of the Skin Sudoriferous and sebaceous glands Hair and hair follicles Nails
Sudoriferous and Sebaceous Glands Sebaceous Glands: (oil glands) found surrounding hair follicles and deposit sebum, oily substance that lubricates the hair and skin, onto the hair shaft Sudoriferous glands: (sweat glands) located in the dermis and secrete a watery substance that is important in body temperature regulation and excretion Four types: Eccrine, apocrine, ceruminous, and mammary glands
Eccrine & Apocrine Glands Eccrine Glands: major sweat glands of the human body; products contain mainly water, salts, and nitrogen-containing wastes Apocrine Glands: don’t become active until after puberty; found only in the axilla, genital area, and areolae of the nipple; products contain lipids and proteins
Ceruminous & Mammary Glands Modified suderiferous glands Ceruminous Glands: Found in ear canal. Produce a waxy substance (cerumen) that prevents foreign substances from entering the auditory canal. Mammary Glands: Found in breasts. Synthesize and secrete milk after appropriate hormonal stimulation.