Lesson 1 Chapter 4 – Integumentary System

LESSON 1 Chapter 4 – Integumentary System Unit 2 Study Guide Integumentary System is divided into two general parts: - cutaneous membrane composed of the dermis and epidermis accessory structures composed of nails, hair, and exocrine gland 4 types of cells: - - - - Keratinocytes: (skin thickening and toughening) produce keratin, a fibrous protein responsible for protective properties. Forms structural of hair. Makes up outer layer of skin. Melanocytes: (contributes melanin – pigment) located at base of epidermis. Synthesize pigment; melanin. Helps protect cells from UV light. Basis for skin colour; more = darker, less = lighter. Langerhans cells: (immune response – macrophages) arise from bone marrow and migrate to epidermis and other parts of body containing stratified squamous epithelial tissue (several layers of flat epithelial cells). They are macrophages and cooperate with T helper cells. Merkel cells: (sensation receptor) Disc-like ending of a sensory nerve fiber, called a Merkel disc, functions as a sensory receptor. Layers of Epidermis “Come Let’s Grow Some Berries!” - Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale (germinativum) 1 LESSON 1 Chapter 4 – Integumentary System 2 Stratum basale is the bottom layer of keratinocytes in the epidermis. It is responsible for constantly renewing epidermal cells. This layer contains just one row of undifferentiated columnar stem cells that divide frequently. Half of the cells differentiate and move to the next layer to begin the maturation process. The other half stay in the basal layer and divide over and over again to replenish the basal layer. Stratum spinosum: Cells that move into the spinosum layer (also called prickle cell layer) change from being columnar to polygonal. In this layer the cells start to synthesize keratin. Stratum granulosum: The cells in the stratum granulosum, or granular layer, have lost their nuclei and are characterized by dark clumps of cytoplasmic material. There is a lot of activity in this layer as keratin proteins and water-proofing lipids are being produced and organized. Stratum lucidum: The stratum lucidum layer is only present in thick skin where it helps reduce friction and shear forces between the stratum corneum and stratum granulosum. Stratum corneum layer are known as corneocytes. The cells have flattened out and are composed mainly of keratin protein which provides strength to the layer but also allows the absorption of water. Layer is responsible for maintaining the integrity and hydration of the skin. LESSON 1 Chapter 4 – Integumentary System 3 Skin Color: Three pigments contribute to skin color: melanin, carotene, and hemoglobin. Melanin ranges in color from yellow to brown to black. Freckles and pigmented moles are local accumulations of melanin. Melanocytes are stimulated to greater activity when exposed to sunlight. Prolonged sun exposure causes a substantial melanin buildup, which helps protect viable skin cells from UV radiation. Despite melanin's protective effects, excessive sun exposure eventually damages the skin. Excessive sun exposure causes clumping of the elastin fibers, leading to "leathery skin", temporarily depresses the immune system, and can alter the DNA of skin cells leading to cancer. The yellowish tinge of skin of some Asian peoples is due to variations in melanin. The pinkish hue of fair skin reflects the crimson color of oxygenated hemoglobin in the red cells circulating through the dermal capillaries. Since fair skin contains only small amounts of melanin, the epidermis is quite transparent and allows hemoglobin's rosy color to show through. The Dermis The second major skin region, is a strong but flexible connective tissue layer. The cell types found in the dermis are fibroblasts, macrophages, and occasional mast cells and white blood cells. Its gel-like matrix is heavily embedded with collagen, elastin, and reticular fibers. The dermis is your "hide" and is richly supplied with nerve fibers, blood vessels, and lymphatic vessels. The major portions of hair follicles, as well as oil and sweat glands, reside in the dermis, but are derived from epidermal tissue. The dermis varies in thickness and it has two major layers: papillary and reticular. Layers of the Dermis: - Papillary: upper layer, contains a thin arrangement of collagen fibers. - Reticular: lower layer, is thicker and made of thick collagen fibers that are arranged parallel to the surface of the skin. LESSON 1 Chapter 4 – Integumentary System 4 Accessory Structures: Exocrine glands, hair, and nails Exocrine Glands of the Skin: - Sebaceous glands – also known as “Oil Glands” - Sudoriferous Glands – also known as “Sweat Glands” 1. Sebaceous Glands (Oil Glands) Most associated with hair follicles. They secrete either into the neck of a hair follicle, or directly onto the surface of skin via pore. Where? Sebaceous glands located over most of the surface of body but not in the palms of hands or the soles of the feet. Secretions? Sebaceous Glands secret an oily substance called sebum. Why Good? Sebum helps to protect skin and hair by: - preventing hairs from becoming too dry and brittle - prevents the skin from becoming dry (by preventing excessive evaporation of water) - restricting the growth/development of certain bacteria 2. Sudoriferous Glands (Sweat Glands) Different Types: - Apocrine glands – ducts open in hair follicles - Merocrine Glands – ducts terminate at sweat pore at the outer surface Where? Apocrine Glands: - Armpits (skin of the axillae) - Pubic region - Pigmented areas of breast (areolae) Merocrine Glands: - Throughout the skin (except for margins of lips, eardrums, nail beds of finger and toe nails) Secretions? Sudoriferous glands secret sweat “perspiration”. Apocrine glands secret a sticky viscous secretion while the secretion from the merocrine gland is thinner watery by comparison. LESSON 1 Chapter 4 – Integumentary System 5 Why Good? The main function of the secretion of sweat are to help regulate body temperature and to help eliminate from the body of some waste products of metabolism (ie. Metabolic reactions) Nails Scale-like modifications of the epidermis that forms a clear protective covering on the dorsum of the distal part of a finger or toe. Each nail has a free edge, a body, and a root embedded in the skin. The thickened proximal part of the nail bed - nail matrix - is responsible for nail growth. Nail cells are heavily keratinized. Nail body slides distally over the nail bed during growth. - Nails grow from nail root, through nail body to a free edge. - Changes to nail appearance can have clinical significance Subcutaneous Layer Also known as hypodermis or superficial fascia It is made up of loose connective tissue; approximately half of the body's fat stores are located in this region. The hypodermis anchors the skin to the underlying organs and allows the skin to move relatively free. It also acts as a shock absorber and insulates the deeper body tissues from heat loss. The hypodermis is not considered part of the skin. Hair follicles and hair can be excluded from your studies. Page 98-101 Hair Distributed over nearly the entire body surface and has some minor protective functions, such as guarding the head against physical trauma, heat loss, and sunlight. Eyelashes shield the eyes and nose hairs help keep dust and other foreign particles out of the respiratory tract.