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The Integumentary System Chapter 5 • Integumentary system is the skin and the organs derived from it (hair, glands, nails) • One of the largest organs – 2 square meters; 10-11 lbs. – Largest sense organ in the body • The study of the skin is Dermatology Functions: 1. Regulation of body temperature – Cellular metabolism produces heat as a waste product . – High temperature • Dilate surface blood vessels • Sweating – Low temperature • Surface vessels constrict • shivering 2. Protection physical abrasion dehydration ultraviolet radiation 3. Synthesis and Storage of Nutrients 4. Sensation touch vibration pain temperature 4. Excretion/ Secretion 5. Immunity/ Resistance 6. Blood Reservoir 8-10 % in a resting adult Epidermis Anatomy • Epidermis Skin • Dermis • Subcutaneous layer or hypodermis Epidermis • Stratum Germinativum (stratum basale) – Single layer of cuboidal to columnar cells – Stem cells that produce keratinocytes – Melanocytes - # the same for all races • Melanin produced in a melanosome • Stratum spinosum (thorn-like, prickly) – 8-10 layers attached by desmosomes • Stratum granulosum – 3-5 layers – Keratinization begins here • Stratum lucidum (lucid = clear) – 3-5 layers of clear cells – Eleidin • Stratum corneum – Dead, flat cells full of keratin Skin Color • Pigmentation – Carotene- an orange-yellow pigment that normally accumulates in epidermal cells. • (i.e. carrots and squashes) – Melanin- a brown, yellow-brown pigment produced by melanocytes. Skin Cancer • Most common form of cancer • Malignant Melanoma- extremely dangerous. • The outlook for long term survival depends on when the condition is detected and treated • Dermal Circulation – Blood with abundant oxygen is bright red, gives skin a reddish tint. – When vessels are dilated, as during inflammation, the red tones become much more pronounced. – When the vessels are temporarily consricted, as when you are frightened, the skin becomes pale. Dermis • Connective tissue layer • Collagen and elastic fibers, nerves, blood vessels, muscle fibers, adipose cells, hair follicles and glands. • Papillary layer – 1/5 of dermis – loose areolar connective tissue – Highly vascular – Dermal papillae - fingerprints • Reticular (net) layer – Dense irregular connective tissue – Both elastic fibers and collagen fibers are present • Other Dermal Components – Sebaceous (oil) glands – Hair follicles – Ducts of sudoriferous (sweat) glands – Striae or stretch marks Subcutaneous Layer (Hypodermis) • Attaches the reticular layer to the underlying organs • Boundary between dermis and hypodermis is indistinct • Consists of loose connective tissue and adipose tissue (“baby fat”) • Major blood vessels and lack of vital organs makes useful method for administering drugs. Accessory organs or epidermal derivatives • Hair and Hair Follicles • Structure: – Hair papilla- peg of connective tissue containing capillaries and nerves. – Hair root- the portion that anchors the hair into the skin – Hair shaft- the part we see on the surface • Hairs grow and are shed according to a hair growth cycle based on the activity level of hair follicles. • Hair in the scalp grows for 2-5 years at a rate of about .3mm per day. • Hair Functions: – Protection from UV light – Insulation – Entry of foreign particles – Touch and sensation – Arrector pilli- “goose bumps” Nails • Plates of highly packed, keratinized cells • Protection, scratching, & manipulation • Formed by cells in nail bed called the matrix ( in area of lunula) • Grows about 1 mm / week • Eponychium - cuticle Skin Glands • Sebaceous (oil) glands – Usually connected to hair follicles – Holocrine glands – Fats, cholesterol, proteins, salts, and cell debris – Moistens hair and waterproofs skin – Sebum- lubricates the hair and skin and inhibits growth of bacteria • Sweat (sudoriferous) glands – Merocrine (eccrine) sweat glands • merocrine glands • Secrete water, salt, wastes • Function is to cool the body (also nervous) – Apocrine sweat glands • • • • Larger, merocrine glands Associated with hair follicles More viscous – fatty acids and proteins Odor occurs when broken down by bacteria • Ceruminous glands – Modified sudoriferous glands – Secrete cerumen (ear wax) • Mammary glands – Secrete milk Wound healing • Inflammation – Blood vessels dilate and become permeable • Heat, redness, swelling and pain • Shallow cuts – Epithelial cells migrate – Contact inhibition Deeper wounds • Inflammatory phase – Fibrin forms clot • Migratory phase – Fibroblasts make granulation tissue • Proliferative phase • Maturation phase • Scars – hypertrophic scar Burns • First degree or partial thickness burn – Only epidermis is damaged – Erythema, mild edema, surface layer shed – Healing – a few days to two weeks – No scarring • Second degree- deep partial-layer burn – Destroys epidermis – Blisters form – Healing depends on survival of accessory organs – No scars unless infected • Third degree or full-thickness burn – Destroys epidermis, dermis and accessory organs of the skin – Healing occurs from margins inward – Skin grafting may be needed • Autograft • Homograft