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BMS 250 Lecture
Chapter 6
| Term | Definition |
|---|---|
| Integumentary system | skin and accessory structures (hair, nails, glands) |
| Integument | covering (cutaneous membrane) |
| Dermatology | the study of skin |
| Layers of the integument | epidermis and dermis |
| Epidermis | composed of keratinized stratified squamous epithelium; most superficial layer of integument with five layers and four cell types |
| Papillary layer | dermis layer composed of areolar CT; superficial region (just deep to the stratum basale) |
| Reticular layer | dermis layer composed of dense irregular CT; deeper, major portion; meshwork that surrounds structures in the dermis |
| Layers of the epidermis from superficial to deep | stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale |
| Which epidermis layers are composed of dead keratinocytes? | stratum corneum and stratum lucidum |
| Which epidermis layers are composed of living keratinocytes? | stratum granulosum, stratum spinosum, stratum basale |
| Cells of the epidermis | keratinocytes, melanocytes, tactile cells, and epidermal dendritic cels |
| Keratinocytes | synthesize the fibrous protein keratin; found in all layers of epidermis (95% of all cells in epidermis) |
| Melanocytes | produce and store pigment melanin; found in stratum basale |
| Tactile cells (Merkel Cells) | detect light touch and pressure; found in stratum basale |
| Epidermal dendritic cells (Langerhans cells) | immune cells; found in stratum spinosum and stratum granulosum |
| Stratum basale | deepest epidermal layer; single layer of cuboidal or columnar cells attached to the basement membrane; contains keratinocytes, melanocytes, and tactile cells |
| Stratum spinosum | contains several layers of keratinocytes that are nondividing and attach to neighbors by membrane junctions, and epidermal dendritic cells that phagocytize pathogens and epidermal cancer cells |
| Stratum granulosum | 3-5 layers of flattened, diamond-shaped cells; process of keratinization begins here; named for cytoplasmic granules (keratin and a lipid-based substance) |
| Stratum lucidum | 2-3 layers of flattened, pale, dead keratinocytes; cells appear featureless with indistinct boundaries; found only in thick skin; contains protein called eleidin) |
| Stratum corneum | most superficial epidermal layer; 20-30 layers of dead keratinocytes; anucleated, tightly packed squamous shape; has a dry, thickened surface that inhibits microorganism growth |
| Keratinocyte life cycle | stem cell in s. basale divides into cell a & b, cell a divides again it pushes cell b from s. spinosum to s.granulosum, away from blood supply and into s. lucidum & corneum where cell b is now dead & filled with keratin & will be shed from apical surface |
| Thin skin | makes up most of the body, lacks stratum lucidum, contains sweat glands, hair follicles, and sebaceous glands, range of thickness is 0.075mm-0.150mm |
| Thick skin | makes up the palms of the hands, soles of the feet, contains all 5 epidermal strata, does not contain hair follicles or sebaceous glands, contains sweat glands, range of thickness: 0.4mm-0.6mm |
| What does skin color result from? | a combination of hemoglobin, carotene, and melanin |
| Melanin | pigment with black, brown, tan, yellow-brown shades, shields keratinocyte DNA from UV radiation; produced by melanocytes in response to UV radiation, transferred to keratinocytes with melanosomes |
| Freckles | over productive melanocyte (too much melanin) |
| Mole (nevi) | clusters of melanocytes (too many melanocytes) |
| Oculocutaneous albinism | congenital disorder causing little to no production of melanin in eyes, skin, and hair (insufficient melanin) |
| Dermis | deep to the epidermis; composed of 2 layers of connective tissue along with collagen fibers, fibroblasts, and dendritic cells (motile) along with blood vessels, sweat and sebaceous glands, hair follicles, arrector pili, nail roots, & sensory nerve endings |
| Dermal papillae | projections of dermis that interlock with projections from epidermis (epidermal ridges) to increase area of contact with epidermis; supplies nutrients to epidermis through capillaries and contains sensory nerve endings for touch |
| Lines of cleavage | tensions lines; natural orientation of majority of collagen fibers and elastic fibers; resist stress, alignment depends on direction of routine stress |
| Subcutaneous layer (hypodermis) | deep to the integument consisting of areolar CT and adipose CT; functions: cushion and protect, energy storage, thermal insulation |
| Where is the common site of drug interactions in the skin? | the subcutaneous layer (hypodermis) |
| Subcutaneous fat | where adipose dominates |
| 1st degree burns | only epidermis; characterized by redness, pain, slight edema, no blisters; ex. minor sunburn |
| 2nd degree burns | epidermis and part of dermis; skin appears red, tan, or white; characterized by painful blisters; ex. severe sunburn, chemical burn, or scalding liquid |
| 3rd degree burns | epidermis, dermis, and hypodermis (possibly deeper); characterized by major tissue damage, scarring, little pain initially; dehydration and infection are major concerns; ex. fire, chemical, or prolonged contact with hot liquid |
| Functions of the integument | protection from injury toxins, pathogens, temp. extremes, and solar radiation, immune function through dendritic cells, prevents water loss or gain, sensation, metabolic regulation through vitamin D production, secretion and absorption, temp. regulation |
| Vitamin D production | upon exposure to UV radiation, keratinocytes synthesize vitamin D3 (cholecalciferol), vitamin D3 is now converted to calcidiol in the liver, and converted to calcitriol in the kidney |
| What substances are discharged through the integument | sweat and sebum |
| Sweat | cools body and excretes some waste products such as salt and urea |
| Sebum | lubricates epidermis and hair and improves water resistance |
| Vasoconstriction | blood vessels diameter narrows, shunts blood away from periphery, helps conserve heat |
| Vasodilation | blood vessel diameter widens, more blood close to the surface, releases excess heat |
| Nails | modifications of stratum corneum that function through protection, manipulation/grasping, and scratching |
| Hair | keratinized cells growing from a follicle in the dermis that function through protection, facial expression, heat retention, visual identification, and sensation |
| Merocrine (eccrine) glands | most numerous, widely distributed sweat glands; discharge sweat onto skin surface; functions: thermoregulation and protection |
| Apocrine glands | secrete by merocrine mechanism, discharge into hair follicles; discharge is viscous, turbid (contains proteins and lipids that are acted upon by bacteria to produce order); function: communication |
| Sebaceous glands | usually discharge into hair follicle; discharge is sebum (oily, waxy, white substance, rich in lipids); functions: lubricate hair, protection |
| Acne | plugged sebaceous duct |
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