The Integumentary System PDF

The Integumentary System Functions: 1. Protection a. Physical barrier (against physical objects) b. Chemical barrier c. Biological barrier (microorganisms) 2. Body temperature and regulation a. Sweating 3. Sensations 4. Metabolic functions a. Encapsul...

The Integumentary System Functions: 1. Protection a. Physical barrier (against physical objects) b. Chemical barrier c. Biological barrier (microorganisms) 2. Body temperature and regulation a. Sweating 3. Sensations 4. Metabolic functions a. Encapsulated nerve endings within the skin 5. Excretion Skin (Integument) - Consists of 3 major regions - Epidermis = superficial regions - Dermis = middle regions - Hypodermis = deepest regions - Subcutaneous layer deep to skin (not technically part of skin) Epidermis - Portion of the skin exposed to the external environment - Outerlayers are completely dead - Composed of keratinized stratified squamous epithelium - Keratinized = dry - Stratified = several different layers - Squamous = top layer of cells are flat - Consists of four cell types and either four or five laters Cells of the Epidermis - Keratinocytes: produce the fibrous protein keratin - Keratin = protein that makes cells waterproof  - Make up 95% of epidermal cells - Langerhans’ cells: epidermal macrophages that help activate sensory nerve endings - Immune cells - Able to move around and look for foreign invaders and digest them - Phagocytic - Merkel cells: function as touch receptors in association with sensory nerve endings - Enable the sensation of very light touch - Melanocytes: produce the pigment melanin - Bottom most layer of epidermis, is stationary - Produces melanin from the amino acid tyrosine by the enzyme tyrosinase (albinos lack this enzyme) - Eumelanin - Brown and black - Pheomelanin - Reddish in color - Melanin acts as a sunblock; blocks UV light - When exposed to sun, melanin is activated UVB - UV Burning - Skin burn/sunburn UVA - UV Aging - Long term Epidermis: thin skin and thick skin - Thin skin: hairy - Four strata - Everywhere else - Non smelly and smelly - Thick skin: non hairy - Five strata - Bottom of feet, palms of hand Thin Skin - Stratum Basale (basal layer) - The deepest epidermal layer firmly attached to the dermis - Single row of the youngest keratinocytes, melanocytes, and Merkel Cells - No blood supply in the epidermis but the stratum basal is very close to the blood supply - Very active, very healthy - Cells undergo rapid division - Alternate name: stratum germinativum - Stratum Spinosum - Keratinocytes contain a weblike system of intermediate filaments attached to desmosomes - Melanocytes fill some or all keratinocytes with melanin - Melanin granules and Langerhans’ cells are abundant in this layer - Stratum Granulosum (granular layer) - Thin; 3-5 cell layers in which drastic changes in keratinocyte appearance occur - Kertohyaline and lamellated granules accumulate in the cells of this layer - Stratum Lucidum (clear layer) - Only appears in thick skin - Thin, transparent band of superficial to the stratum granuloma - Cells contain Eleidin - Consists 3-5 rows of flat, dead keratinocytes - Stratum Corneum (horny layer) - Many layers of dead keratinocytes containing keratin - Accounts for ¾ of epidermal thickness - Functions: - Waterproofing - Protection from abrasion and penetration  - Rendering the body relatively insensitive to biological, chemical, and physical assault - Cells slough off (66,000 per min) - Average person loses 120 lbs of skin cells in their lifetime Dermis - Second major skin regions containing strong, flexible connective tissue - Cell types: fibroblasts, macrophages, and occasionally mast cells and white blood cells - Composed of two layers: papillary and reticular Layer of Dermis - Papillary Layer - Areolar connective tissue with collagen, elastic, and reticular fibers - Its superior surface contains nipper-like projections called dermal papillae - Dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings - Reticular Layer - Makes about 80% of the thickness of the skin - Dense irregular connective tissue - Elastin fibers provide stretch-recoil properties - Has Pacinian corpuscles which detect pressure Meissner’s Corpuscle Suderiferous Glands (sweat) Sweat is made up of 90% water, NaCl, vitamin C, antibodies, dermcidin, metabolic w - Apocrine sweat glands - Produce odorous secretion - Pheromones - Become active during puberty - Merocrine (eccrine) sweat gland - Sensible perspiration  - Non-odorous - All over the body Modified Sweat Glands - Ceruminous glands: modified apocrine glands in external ear canal that secrete cerumen (earwax) - Mammary glands: specialized sweat glands that secrete breastmilk Sebaceous Glands - Simple alveolar glands found all over the body - Soften skin when stimulated by hormones - Secrete an oily secretion called sebum Hypodermis - Subcutaneous layer deep to the skin - Composed of mainly adipose and areolar connective tissue - Functions to absorb shock, insulate, store energy - Site of subcutaneous injections