1. INTEGUMENTARY SYSTEM “THE STRUCTURE OF OUR SKIN”

2. http://vrc.belfastinstitute.ac.uk/resources/skin/skin.htm

3. Structure of the skin Is the largest and thinnest organ in the body appendages: hair, nails, glands one square inch of skin contains more structures than some entire organs thick skin produces prints and has no hair cutaneous membrane referred to as the integument

4. Structure of the skin Layers of the skin: –epidermis: outermost, made of a thin sheet of stratified squamous epithelium –dermis: deepest layer, thicker, made mostly of connective tissue subcutaneous layer: lies beneath the dermis –made mostly of loose and adipose tissue –insulates, stores energy, shock absorber

5. Epidermis Keratinocytes: (cells of the epidermis) contain keratin: a tough fibrous protein Melanocytes: cells that produce pigment Langerhans cells: macrophages activate immune system Merkel cells: occasionally; touch Desmosomes: cell junctions which hold epidermal cells together Strata: layers

6. Cell layers of the epidermis 1. Stratum corneum; outer most layer of skin –cells continually flake off –millions of epithelial cells reproduce daily to replace the ones shed 2. Stratum lucidum: clear layer –found in thick skin –Palms, finger tips, soles of feet

7. Cell layers of the epidermis 3. Stratum granulosum: keratinization begins 4. Stratum spinosum: base layer –only layer where mitosis occurs –new cells move toward surface 5. Stratum germinativum: growth layer –combo of spinosum and basale

8. Epidermal growth and repair Millions of dead cells rub off every day. Takes about 35 days to regenerate skin this process will speed up if skin is damaged calluses form when mitotic activity increases due to friction…thickening of the epidermis

9. Dermis Deeper of the two layers and much thicker –Papillary Layer & Reticular Layer Richley supplied with nerve fibers, blood vessels, & lymphatic vessels. Major portion of hair follicles, oil & sweat glands reside in the dermis. Binds the entire body together.

10. Layers of the dermis 1. Papillary layer: made of collagenous and elastic fibers –when elastic fibers decrease wrinkles develop –dermal papillae: parallel rows of projections binds skin layers together form ridges and grooves for prints ridges develop before birth and never change allow us to walk upright and grip things

11. Layers of the dermis 2. Reticular layer: dense layer of tough and interlacing white collagenous fibers –arrector pili muscles: muscle that contracts only when your are frightened or cold (goosebumps) –Accounts for 80% of the thickness of the dermis. –Cleavage (tension lines) important for surgeons & patients…skin gaps less when incisions are made along these invisible lines.

12. Dermal growth and repair Doesn’t continually regenerate as epidermis does, only during the healing process Langer’s lines (cleavage lines): patterns formed by the white collagenous fibers –incisions made parallel to cleavage lines will heal better elastic fibers that are stretched will weaken and tear (stretch marks)

13. Skin color Pigments involved: Melanin: determines skin color –number of melanocytes is the same, but the amount of pigment produced varies from person to person Black & brown skinned produce more and darker melanosomes Freckles & Moles…accumulation of melanin. Carotene: yellow-orange pigment Found in palms & soles of our feet Variation in melanin & carotene give Asians a yellowish tinge of the skin.

14. Skin color Hemoglobin Fair skinned pinkish hue from oxygenated blood Factors –heredity –Sunlight simulates melanocytes –hormones produced by the pituitary gland –age

15. Alterations of Skin color Cyanosis: decrease in blood flow causes the skin to turn bluish gray…respiratory Erythema: (blushing) emotion, fever, allergy, or hypertension. Pallor: (pale skin) stress, low blood pressure Jaundice (yellow) liver disorder Bruises: reveal where blood escaped from circulation & clotted beneath skin.