Chapter 3 - The Integumentary System PDF

Chapter 3 The Integumentary System  The integumentary system  The integumentary system is the skin and its accessory structures, which provide the body with overall protection. Integumentary System Includes:  Skin  Subcutaneous tissue below the skin  Accessor...

Chapter 3 The Integumentary System  The integumentary system  The integumentary system is the skin and its accessory structures, which provide the body with overall protection. Integumentary System Includes:  Skin  Subcutaneous tissue below the skin  Accessory Structures: Sweat glands Sebaceous or oil glands Hair Nails  Layers of the Skin  Skin is composed of Three major layers: 1. Epidermis: made of closely packed epithelial cells 2. Dermis: made of dense, irregular connective tissue 3. Hypodermis: made mainly of loose connective and fatty tissues Layers of the Skin  Layers of the Skin 1) Epidermis  Composed of keratinized, stratified squamous epithelium.  Has no any blood vessels within it  Made of 4 to 5 layers of epithelial cells (from deep to superficial); a) Stratum basale Thin b) Stratum spinosum skin c) Stratum granulosum d) Stratum corneum Thick e) Stratum lucidum skin  Layers of the Skin 1) Epidermis - keratinocyte: is a cell that manufactures and stores the protein keratin - Melanocytes: cells that produce melanin, the pigment primarily responsible for giving skin its color  Layers of the Skin 2) Dermis  Connects the epidermis to the hypodermis.  It contains blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands  Provides strength & elasticity due to the presence of collagen & elastin fibers.  Has only two layers: a) Papillary layer b) Reticular layer  Layers of the Skin 2) Dermis - Papillary layer: made of loose, areolar connective tissue, which means this layer's collagen and elastin fibers form a loose mesh. - Reticular layer: is well vascularized and has a rich sensory and sympathetic nerve supply  Layers of the Skin 3) Hypodermis  (also called the subcutaneous layer or superficial fascia) is a layer directly below the dermis and connects the skin to the underlying fascia (fibrous tissue) of the bones and muscles.  The hypodermis consists of well-vascularized, loose connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument  Accessory Structures of the Skin  Accessory structures of the skin include: 1. Hair: Dead keratinized cells 2. Nails: Dead keratinized cells protect fingers & toes 3. Sweat glands: produce sweat that cools the body 4. Sebaceous glands: produce sebum act as a natural moisturizer  Accessory Structures of the Skin 1. Hair Structure Arrector Pilli The smooth muscle that is activated in response to external stimuli that pull on hair follicles and make the hair “stand up”  Accessory Structures of the Skin 2. Nails Structure The nail body is formed on the nail bed and protects the tips of our fingers and toes  Accessory Structures of the Skin 3. Sweat Glands Structure Produce sweat to cool the body Two type of glands: A. Eccrine sweat gland is type of gland that produces a hypotonic sweat for thermoregulation B. Apocrine sweat gland  is usually associated with hair follicles in densely hairy areas, such as armpits and genital regions  Apocrine sweat includes organic compounds that make the sweat thicker and subsequent smell  Accessory Structures of the Skin 4. Sebaceous Glands Structure Oil gland that is found all over the body and helps to lubricate and waterproof the skin and hair. Generate and excrete sebum, a mixture of lipids, onto the skin surface, thereby naturally lubricating the dry and dead layer  Functions of the Integumentary System The skin plays important roles in: 1. Protection: First layer of defense to prevent dehydration, infection, and injury to the rest of the body. 2. Sensing stimuli Skin acts as a sense organ because the epidermis, dermis, & hypodermis contain sensory receptor such as Meissner corpuscle & Merkel (Touch), Pacinian corpuscle (vibration), free nerve ending (Tem & pain). 3. Vitamin D synthesis When exposed to UV radiation. In the presence of sunlight, vitamin D, which is necessary for our well-being but not easily available in natural foods  Functions of the Integumentary System 4. Thermoregulation Sweat glands, dilation or constriction of heat-carrying blood vessels in the skin, adipose fat.