Anatomy Chapter 5

first line of defense aainst a hostile environment - cutaneous membrane and accessory structures

• 1. protect
• 2. excrete
• 3. regulate temperature
• 4. synthesis of vitamin D₃ 
• 5. storage of nutrients
• 6. touch sensation (pressure, pain, temperature)

stratified squamous

• the epidermis is:
• a) vascular
• b) avascular - cells rely on the diffusion capillaries within the dermis

contains 5 layers found on the soles and palms

contains only 4 layers found everywhere except soles and palms

a result of epidermal pigmentation

brown color

can be converted to Vitamin A - yellow

• cells flatten and fill with the protein keratin as they rise to the surface:
• stratum germinativum
• stratum spinosum
• stratum granulosum
• stratum lucidum
• stratum corneum

aka basale - deepest epidermal layer, attached to the basmement mebrane (dermis

layers of the epidermis touching the ridges of the dermal papilla layer of the dermis

stem cells that are constantly dividing - part of the stratum germinativum

function as touch sensitive receptors for the nervous system within the stratum germinativum layer of the epidermis

produce melanin when stimulated by UV light

superficial to the stratum germinativum (8-10 layers of cells)

produce keratin which is used for structure and water resistance

stimulate and assist the immune system upon penetration by pathogens

3rd epidermal layer - where cells fill with keratin and die

extra layer in thick skin - cells completely filled with keratin

exposed surface of both thick and thin skin, 15-300 layers of keratinized cells, protective barrier of dead, durable and expendable cells protecting underlying epidermal layers, constantly being sloughed or shed off (15-30 days to rise, stay for approximately 2 weeks)

• 1. promote the divisions of germinative cells
• 2. increase the production of keratin
• 3. stimulate secretion by epithelial glands
• 4. stimulate epidermal repair after injury

contains blood vessels, glands, and accessory structures - lies between the epidermis and the subcutaneous layer

• 1. papillary layer
• 2. reticular layer

composed of loose connective tissue - meissner's corpuscles

composed of dense irregular connective tissue - pacinian corpuscles

sensitive to light touch

sensitive to deep pressure and vibration

aka: hypodermis - consists of adipose and areolar tissues - very elastic

• 1. hair
• 2. glands
• 3. nails

approx. 5 million that have very little function (slightly insulate skin surface, provide UV protection, filter air the passes into/by the body surface)

above surface

below surface

• 1. vellus hair
• 2. terminal hair

fine, lightly pigmented - covering the majority of the body surface

thick, pimented - found on top of head, eyebrows, eyelashes

remains attached and growing for 2-5 years (average adult scalp loses approx. 50 hairs a day)

determined by the type and amount of melanin produced by the follicle

pigment production slowing with age - bubbles are produced in the medullary (middle layers)

where hair originates - deep through the dermis and into the hypodermis terminating at the bulb

muscles associated with each hair root - can be pulled upright to cause goosebumps

hard, dead, keratinized cells that cover hairs

contains hard keratin

contains soft, flexible keratin

• 1. sebaceous (oil) glands
• 2. sudiferous/sweat glands
• 3. mammary glands
• 4. ceruminous glands

oil glands - secrete sebum (waxy, oily substance) into the hair follicle by holocrine secretion - functions to keep hair and skin smooth and supple

• a. apocrine
• b. merocrine

located in pubic and axillary areas - begin to secrete sticky, cloudy, odor-producing secretions into hair follicles at puberty

located over entire body surface, but highly concentrated on palms and soles - secrete sweat directly to skin surface

modified apocrine glands whose secretions are highly regulated by ffemale sex hormones

modified sweat glands that secrete cerumen (earwax) in external auditory canal

plates of keratin located on the dorsal ends of fingers and toes that protect digits from mechanical stress

• Epidermis thins
• Vitamin D3 levels decrease by 75%
• Melanocyte activity declines, skin becomes pale
• Glandular activity declines
• Merocrine sweat glands are less active, older people cannot loose heat as fast as young people
• Blood supply to the dermis is reduced
• Hair follicles stop functioning or produce thinner, finer hairs, hair grays
• Dermis thins
• Secondary sexual characteristics fade
• Skin repairs proceed slowly, recurring infections may result.