Anatomy Ch 5

Skin and accessory structures - hair, nails, glands, muscles, nerves

• Epidermis - contains epithelial tissue
• Dermis - contains connective tissue

• skin
• largest organ in both surface area and weight

• deep to the dermis - not part of the skin
• consists of areolar and adipose tissue
• storage depot for fat - large blood vessels that supply the skin

• nerve endings in the subcutaneous layer that are sensitive to pressure

• majority of cells in the epidermis
• produce keratin
• produce lemellar granules - release a water-repellent sealant that decreses water entry and loss

keratin is a tough protein that helps protect the skin and underlying tissue

• produce melanin - pigment - yellow-red or brown-black
• melanin absorbs damaging UV light
• melanocytes produce melanin and secrete it to the keratinocytes in granular form
• melanin shields keratincytes from UV light
• 8% of epidural cells

• involved in immune response - flag pathogens for other cells to destroy
• start in red bone marrow - migrate to epidermis - small amount

• specialized cell type - work in conjunction with nerves to detect touch sensation
• tactile (Merkel) disk - the sensory neuron that the Merkel cells work with

• skin on most regions of body
• Has four strata:
• 1. stratum basale
• 2. stratum spinosum
• 3. stratum granulosum
• 4. thin stratum corneum

• skin where exposure to friction is great - fingers, soles of feet
• No sabaceous glans and no hair folicles
• Sudoriferous glands (sweat glands) are present
• Has 5 layers:
• Stratum Basale
• Stratum spinosum
• stratum granulosum
• stratum lucidum
• thick stratum corneum

• made of keratinized stratified squamous epithelium
• 1. Stratum Basale - single layer
• 2. stratum spinosum - 8 to 10 layers
• 3. stratum granulosum - 3 layers
• 4. stratum lucidum -thick skin - 3 -5 layers
• 5. stratum corneum - 25-30 layers

• deepest layer of epidermis
• also called stratum germinativum - single layer
• mitotic division - one cell stays anchored and the other moves superficially to surface of skin

• keratinocytes - second deepest layer
• live cells
• look spiny when separated because of intermediate filaments connecting cells via desmosomes

• mix of dead and live cells
• flattened keratinocytes undergoing apoptosis (programmed cell death)
• keratinocyes - lemellar granules - secrete water-repellent sealant that decreses water entry and loss
• keratohyalin - protein that converts tonofilaments (internediate filaments) into keratin

• only in thick skin - dead keratincytes that have a large amount of keratin - tough cells
• no sebatious glands or hair folicles

• most superficial layer of epidermis
• dead, flat, keratin filled - waterproofed
• continuously shed and replaced by deeper cells

• accumulation of keratin in cells as they move from one epidermis layer to the next
• undergo apoptosis and slough off after dead and keratinized
• Takes 4 weeks for cell to travel from stratum basale to stratum corneum and slough off

hormone-like protein that regulates epidermal cell division rate and increases it when epidermis is damaged

• deeper part of skin - composed of connective tissue
• blood vessels, nerves, glands, and hair follicles in this layer
• composed of:
• 1. papillary region
• 2. reticular region

• the most superficial of two regions of connective tissue in the dermis
• 20% of dermal layer
• Areolar CT
• Dermal papillae - nipples - project into epidermis - cause epidermal ridges
• Epidermal ridges - ridges on epidermis - fingerprints
• Meissner corpuscles - corpuscles of touch - tactile receptors in dermal papillae that are sensitive to touch
• Free nerve endings - dentrites (receptor part of neuron) that lack structural specialization - initiate signals that give rise to sensations of warmth, coolness, pain, itching

• part of the dermis - attached to the subcutaneous layer
• dense irregular CT
• contains collagen and elastic fiber that give skin extensibility and elasticity
• extensibility - ability to stretch
• elasticity - ability to return to original shape after stretching

organelle of melanocytes that synthesize melanin

mole - round, flat, or raised area - results form an overgrowth of melanocytes

• carrier protein RBC
• oxygen-carrying pigment in red blood cells
• when highly oxigenatied give red or pink color to skin - pale people done have enough melanin to cover it

• yellow- orange pigment that gives egg yolks and carrots color
• precursor of vitamin A

• albinos have normal amount of melanocytes - not producing melanin at all
• vitiligo - lack of melanocytes

• skin turns blue
• not enough oxygen in blood (stopped breathing)
• blood moves to organs and away from skin (cold)

• skin looks yellow
• buildup of yellow pigment bilirubin - liver disease - liver not removing bilirubin from blood

• skin looks red
• incresed blood flow to area due to skin injury, exposure to heat, infection, inflammation, allergic reaction

• pale skin
• shock and anemia

• Hair

• shaft - superficial portion of hair that projects above surface of skin
• root - portion of hair deep to the shaft - pentrates into dermis
• hair follicle - surrounds the root of the hair - made of external root sheath and internal root sheath - together called the epithelial root sheath

• dense dermis surrounding the hair follicle
• bulb - base of each hair follicle - onion-shaped structure
• papilla of the hair - nipple-shaped indentation in the bulb - areolar CT and blood vessels that nourish growing hair follicle
• matrix - in the bulb - stratum basale - responsible for growth of hair

muscle which contracts under physiologic or emotional stress causing the hair shaft to be perendicular to the skin surface - goose bumps

dentrites of neurons that surround each hair follicle - sensitive to touch

• lanugo - fine hair covering the body of the fatus - shed before birth
• vellus hairs - short fine hair that covers body (infancy through adulthood)
• teminal hair - thick coarse hair - head, face, pubic areas

• alopecia - partial or complete lack of hair - caused by genetic factors, aging, endocrine disorders, chemotherapy, skin disease
• hirsutism - a condition of excessive body hair

• oil glands - epithelial cells that secrete sebum
• usually connected to and opens into a hair follicle
• Sebum - oily substance that coats hairs to keep from drying - also covers skin to stop excessive evaporation of water, inhibits growth of certain bacteria, keeps skin soft and pliable

• sweat glands - three to four million in body - release perspiration into hair follicles or onto skin surface
• 1. Eccrine sweat gland
• 2. Apocrine sweat glands

• most regions of body - esp forehead, palms, soles
• simple, coiled tubular glands - deep dermis - terminates at surface of epidermis
• Regulates body temp, waste removal
• functions soon after birth

• axilla (armpit), groin, areolae, beard
• simple, coiled tubular glands - subcutaneous layer - terminates in hair follicle
• emotional stress & sexual excitement
• funtions at puberty

• insensible perspiration - sweat that evaporates before it is perceived
• sensible perspiration - sweat excreted in larger amounts and is seen as moisture on the skin

• sweat glands in external ear - produce a waxy secretion
• cerumen - earwax -combined secretions of ceruminous and sebaceous glands

• plates of tightly packed, hard, dead, keratinized epidermal cells

• 1. Nail body - visible portion
• 2. free edge - extents past distal end of digit
• 3. nail root - buried in a fold of the skin
• 4. lunula - little moon - white area caused by thicker nail in that area
• 5. hyponychium - secures nail to fingertip
• 6. eponychium - cuticle - narrow band of epidermis that expands from and adheres to the margin of the nail wall
• 7. nail matrix - deep to the nail root - mitosis to produce nail growth

• reduce heat loss
• protects eyes, nose, ears
• senses light touch

• 1. Thermoregulation - via sweat glands and modified blood flow
• 2. Protection - from heat, dehydration, microbes - langerhans cells, microphages
• 3. Cutaneous sensations - cold, hot, pressure, pain
• 4. Excretion and Absorption -excretes water, ammonia, urea - absorbs lipid soluble vit A, D, E, K, cortizone, toxins
• 5. Synthesis of Vit D - liver and kidneys use UV rays to prodice calcitriol - hormone that aids in absorbtion of calcuim

dermis houses extensive newwork of blood vessels - carry 8-10% of total blood flow

epidermal injury - basal cells around wound break contact with basement membrane and migrate across wound until they encounter one another - contact inhibition causes them to stop migrating

• wound that extends to dermis and subcutaneous layer
• 1. inflammatory phase - blood clot forms and loosely unites edge of wound
• 2. migratory phase- clot becomes scab, epithelial tissue migrate under scab to bridge wound. Tissue filling the wound is called granulation tissue
• 3. proliferative phase - extensive growth of epithelial cells beneath scab
• 4. maturation phase - scab sloughs off - blood vessels restored to normal

vascular and cellular response that helps eliminate microbes, foreign material, and dying material in prep for repair

• process of scar tissue formation
• Hypertrophic scar - a scar that remains within the boundaries of the original wound
• keloid scar - scar tissue that extends beyond the bounderies into normal surrounding tissue