Integumentary System Integumentary System n Skin n Epidermis

Integumentary System

Integumentary System n Skin n Epidermis Dermis Accessory structures (appendages) n n n Glands Hair Nails

Epidermis n n n Outermost layer of the skin Comprised of epithelial cells Contains no blood vessels (avascular) n n n Nutrients diffuse over from dermal blood vessels Is thicker in areas of significant wear and tear (palms of hands and soles of feet) Keratin n n Protein that replaces epidermal cell cytoplasm in order to thicken and protect the skin Also comprises hair and nails

Epidermis – Thick vs. Thin Skin n Thick Skin (aka, glabrous [hairless] skin) n 5 layers n n n Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale (stratum germinativum) Thin Skin (aka, vellus [hairy] skin) n 4 layers (stratum lucidum is absent and stratum corneum is much thinner)

SC SG SL SS SB Dermis

Epidermis Thick Skin Thin Skin

Epidermal Cells n Keratinocytes n n n Melanocytes n n n Major epidermal cell type ~28 day transit time from stratum basale to stratum corneum Scattered between cells of stratum basale Contain organelles called melanosomes, in which the melanin pigment is synthesized Melanosomes are quickly released and phagocytized by neighboring keratinocytes (epidermal melanocytes do not retain their melanosomes) Langerhans cell – involved in immune response Merkel cell – touch receptor

Epidermal Cells Melanocyte Keratinocytes

Melanin in Stratum Basale Keratinocytes

Dermis n Comprised of elastic connective tissue n n Allows for skin to stretch Contains blood vessels (vascular) and nerves (innervated) Location of accessory structures (sweat glands, oil glands, and hair) Dermal papillae n n Extensions of dermis into epidermal layer Are what form fingerprints

Dermis

Dermal Papillae

Hypodermis aka, subcutaneous layer n NOT part of the skin n Connects skin to surface muscles n Consists of loose connective tissue and fat (adipose) tissue n

Burns n 1 st Degree (aka, superficial partial-thickness) n n n 2 nd Degree (aka, deep partialthickness) n n n Epidermis and possibly a portion of dermis Tissue is reddened and may blister Epidermis and portions of dermis Tissue is blistered and broken 3 rd Degree (aka, full-thickness) n n Full skin and possibly subcutaneous tissue Tissue is broken, dry and pale, or charred Rule of Nines – estimate % of body surface area in treatment of burns

Accessory Structures (appendages) n Glands n n Sebaceous (Oil) Sudoriferous (Sweat) n n Eccrine Apocrine Hair n Nails n

Sebaceous (Oil) Glands n Sebum – oily secretion n n Lubricates skin and coats hair Prevents drying It is believed that bacterial lipases break down triglycerides of sebum into irritative fatty acids that cause acne. Ducts open into hair follicles Meibomian glands n n Modified sebaceous glands Lubricate eyes

Questions to answer (place on separate paper and turn them in on the way out) 1) Why is a third degree burn so much more devastating than a first degree burn? (Answer based on the specific skin layers and structures involved. ) 2) Why does washing your hair actually damage it? How do we treat this damage?

Sebaceous (Oil) Glands

Sudoriferous (Sweat) Glands Cool the body via evaporation n Eccrine Sweat Glands n n Distributed over entire body except lips and parts of external genitalia Ducts open directly onto surface of skin Excrete salts, urea, ammonia, and uric acid along with water

Sudoriferous (Sweat) Glands (cont. ) n Apocrine Sweat Glands n n n Located in armpits (axillae), nipples, and groin area Duct empties into hair follicle superficial to sebaceous gland Become active at puberty Secretion is initially odorless; bacteria on the skin metabolize secretory products to produce malodorous compounds Secrete in response to emotional stimuli (not heat) Modified apocrine sweat glands n n n Ceruminous glands – ear canal; produce cerumen (ear wax) Ciliary glands - eyelids Mammary glands – produce milk (breasts)

Hair n Two types in adults n n n Vellus hairs – thin, short and poorly pigmented Terminal hairs – thicker, longer and more heavily pigmented Composed mainly of “hard keratin” (as opposed to “soft keratin” in the epidermal cells) Arrector pili muscle causes hair to raise, forming goose bumps Hair color is determined by relative amounts of eumelanin (black/brown) & pheomelanin (reddish color)

Hair (cont. ) n n n Shaft – portion of hair above the skin Root – portion of hair below the skin Follicle – sheath of epithelial and connective tissue that surrounds the hair Bulb – located at base of follicle Three phases in life cycle of each hair n n n Anagen – the period of active growth (0. 04 cm per day) Catagen – the period of involution (degeneration) when the lower part of the follicle below the arrector pili muscle atrophies Telogen – the resting period between the end of follicular atrophy and the shedding of the hair

Hair

Nails n n n Comprised of hard keratin from stratum corneum Nail plate – hard portion of nail Nail bed n n Comprised of stratum basale and stratum spinosum Nail plate rests on the nail bed Nail root – proximal part of nail (covered by skin) Nail matrix – contains stem cells that cause nail to grow

Nails

Functions of Skin n n Protect against infection Protect against dehydration n n Regulate body temperature n n Membrane-coating granules (MCG’s) seal spaces between keratinocytes to prevent entry of pathogens and loss of water Vasoconstriction (blood vessels become narrower) – conserve heat Vasodilation (blood vessels open wider) – promotes radiation/dissipation of heat to surrounding air Sweat Sensory reception n Pain Temperature changes Touch (and pressure)

Skin Discoloration Albinism – lack of melanin production due to genetic mutation n Cyanosis – bluish skin color due to decreased O 2 in blood n Jaundice – excessive bile pigments (bilirubin) in the blood causes skin to turn yellow in color n

http: //www. albinism. org/

Cyanosis

Jaundice

(Colloidal Silver Staining)

Skin Disorders n Dermatitis (aka, eczema) n n n Inflammation of the skin Due to irritants such as oil of poison oak or poison ivy, detergents, acids, etc. Atopic Dermatitis n n n Intense itching Skin inflammation Crusting of skin surface

Atopic Dermatitis

Skin Disorders (cont. ) n Psoriasis n n n Faster than normal renewal of cells resulting in accumulation of cells in the stratum corneum Produces red (erythematous), flat areas (plaques) covered with silvery scales Unknown etiology (cause)

Psoriasis

Skin Disorders (cont. ) n Cancer n Basal cell carcinoma – originates in stratum basale n n Squamous cell carcinoma – originates in stratum spinosum n n Caused by UV radiation Caused UV radiation or chemical agents Melanoma – malignant tumor of melanocytes n n n Originates in a mole/birthmark (nevus) Irregular in shape Rapidly dividing cells

Skin Cancer Basal cell carcinoma Malignant melanoma Squamous cell carcinoma

Skin Disorders (cont. ) n Wart (aka, verruca) n n Small tumor Caused by viruses of the human papillomavirus (HPV) family