The Integumentary System VNSG 1420 Anatomy & Physiology Chapter 5

Integumentary System Skin & appendages Glands, hair & nails Blood vessels, nerves & sensory organs Integument means covering Cutaneous refers to the skin as a whole Skin is largest organ of the body

Structure of the Skin Two layers Epidermis -- outermost portion with thin layer subdivisions called strata Composed entirely of epithelial cells, contains no blood vessels Dermis – true skin – framework of connective tissue Contains blood vessels, nerve endings & glands

Epidermis Surface layer of the skin Stratum basale – deepest layer has the only living cells in the epidermis New cells multiply (grow in number) by dividing & accumulate keratin, thicken & die as they push up to the surface Only layer of cells that reproduces

Epidermis Contain melanin pigment Protects cells from harmful ultraviolet radiation Stratum corneum – thick, uppermost, outer layer of epidermis

Dermis Deeper layer of skin (also called corium or true skin) with a framework of elastic connective tissue with blood vessels, nerves endings, hair follicles & glands Dermal papillae – extensions form a distinct pattern of ridges on thick skin (fingerprints & footprints) Thickness of dermis varies in areas Thin eyelids, thick soles & palms

Subcutaneous Layer Known as hypodermis/superficial fascia Consists of loose connective & adipose (fat) tissues, blood vessels & nerve endings Fat serves as insulation & reserve energy supply Dermis rests on subcutaneous tissue that connects the skin to superficial muscles, no clear boundary between dermis & subcutaneous layer

Accessory Structures of the Skin Sweat glands Sebaceous glands Hair Nails

Sebaceous Glands Lubricate skin & hair, prevent drying Sac-like structures with sebum - oily secretion, ducts open into hair follicles Vernix caseosa --cheese-like covering produced by sebaceous glands before birth Blackheads & pimples form from sebum & keratin blocking glands Cysts - sac of sebum blocking gland

Sweat Glands Sudoriferous glands - coiled, tubular in dermis & subcutaneous tissue Excretory tube extends to skin surface & opens at a pore Regulate body temperature through sweat evaporation from body surface Water, mineral salts & other wastes make up sweat

More on Sweat Glands Sweat glands in axilla (armpits) & groin release their secretions through hair follicles in response to emotional stress & sexual stimulation (apocrine glands) Their secretions contain cellular matter broken down by bacteria & produce body odor

Modified Sweat Glands Ceruminous glands Produce cerumen (ear wax) in ear canals Ciliary glands Located at edge of eyelids Mammary glands

Hair Composed mainly of keratin & is not living Serves as insulation Develops in sheath called follicle from cells at bottom of follicle Grows from follicular cells at follicle base Arrector pili muscle (involuntary) is attached to most hair follicles -- causes goose bumps when muscle contacts

Nails Made of keratin, originate in outer layer of epidermis Produced by epidermal cells at proximal end of nail called nail root Changes in nail signal changes in health status & occur in chronic disease Color, thickness, shape & texture

Functions of the Skin Four major functions Protection against infection Protection against dehydration Regulation of body temperature Collection of sensory information

Protection Against Infection Intact skin is primary barrier against infection Main defense against pathogens Constant shedding of surface cells --mechanical removal of pathogens Protects body from harmful chemicals & toxins in environment Non intact skin invites infection of deeper tissues

Protection Against Dehydration Preventing water loss maintains the wet environment needed by all cells Keratin & sebum act as lubricants for skin Waterproof & prevent fluid loss by evaporation

Regulation of Body Temperature Allows loss of excess heat & protects from cold environment (thermoregulation) Skin blood supply size changes are involved in temperature regulation Blood vessels dilate (widen) for heat to dissipate & cool Constrict (narrow) to diminish heat loss in cold conditions Perspiration from sweat (eccrine) glands cools

Collection of Sensory Information Free nerve endings & special receptors for touch, pain, pressure & temperature are located in dermis Skin is chief sensory organ of body Skin sensory reflexes work with brain & spinal cord for adjustment to the environment

Collection of Sensory Information Free nerve endings & special receptors for touch, pain, pressure & temperature are located in dermis Skin is chief sensory organ of body Skin sensory reflexes work with brain & spinal cord for adjustment to the environment

Other Activities of Skin Absorption of medications -- topical creams & patches & subcutaneous injections Excretion of water & electrolyte salts in perspiration & nitrogen-containing wastes Manufacture of Vitamin D from ultra-violet sunlight rays No breathing or gas exchange occurs

Observation of the Skin Color, texture & condition should be observed Amount of pigment melanin in epidermis, hair & iris of eye Surface blood supply quantity & composition Oxygen, hemoglobin, presence of bile or other chemicals Melanin protects from sun damage

Effects of Aging Skin changes occur from loss of collagen & fat in tissues, becomes thinner & loses elasticity Pigments  with age in skin & hair More sensitivity to cold due to  fat & poor circulation Hair & skin dry from lack of sebum Nails become brittle, flake, thicken or discolor

Care of the Skin Ensure good general health & prevent disease Proper nutrition Adequate circulation Regular cleansing & good hand washing Protection from sunlight exposure Sunscreens and sunblock Protective clothing & hats