Unit 5: Key Terms
Cutaneous membrane (skin)
two main components (epidermis, dermis)
Epidermis
superficial layer, keratinized stratified squamous epithelium resting on basement membrane
Dermis
deep to epidermis and basement membrane, loose connective tissue and dense irregular connective tissue
Arrector pili muscles
small bonds of smooth muscle associated with hair
Hypodermis
subcutaneous fat, deep to the dermis, not part of the skin, made of loose connective and adipose tissues
Functions of integumentary system
protection, glands, sensation, thermoregulation, excretion, vitamin D systhesis
Keratinocytes
make up about 95% of the epidermis, make the epidermis stronger and less susceptive to mechanical trauma, manufacture keratin
Stratum corneum
outermost layer, dead keratinized cells
Stratum lucidum
only in thick skin, palms, soles
Stratum granulosum
flattened/ granular
Stratum spinosum
looks spiny under a microscope
Stratum basale
deepest, mitotic layer
Keratinocyte life cycle
stratum corneum continuously sheds dead cells, must be replaced to maintain integrity of epidermis, replaced by mitosis
Dendritic cells
in stratum spinosum, phagocytes of immune system, protect skin and deeper tissues from pathogens
Merkel cells
oval cells scattered throughout stratum basale, sensory receptors associated with small neurons in dermis, found in finger tips, lips, base of hairs
Melanocytes
in stratum basale, produce melanin
Melanin
protein pigment ranging from orange-red to brown-black
Thick skin
about as thick as a paper towel, all 5 epidermal layers, very thick stratum corneum, no hair follicles, many sweat glands
Thin skin
covers areas of body not subjected to as much mechanical stress, about as thick as a sheet of printer paper, only 4 layers (no stratum lucidum), numerous hairs, sweat glands, sebaceous glands present
Callus
additional layers of stratum corneum, forms in either thick or thin skin in response to repetitive pressure
Dermis
high vascular layer deep to epidermis, provides blood supply, contains sensory receptors, anchors epidermis in place, 2 distinct layers, 2 types of connective tissue
Papillary Layer
thinner, most superficial of 2 layers
Dermal papillae
tiny projections at surface of papillary layer
Capillaries
tiny blood vessels
Tactile (Meissner) corpuscles
in dermal papillae, sensory receptors, respond to light touch stimuli, more numerous where sensation is primary function
Reticular layer
deep, thicker layer, separates dermis from hypodermis, mostly dense irregular connective tissue, largely irregularly arranged collagen bundles
Lamellated (Pacinian) corpuscles
sensory receptors embedded within reticular layer, respond mainly to changes in pressure and vibration
Dermal ridges
areas where dermal papillae are most prominent due to presence of thick collagen bundles
Epidermal ridges
indent overlying epidermis to create this, enhance gripping ability of hands and feet
Melanin
produced by melanocyte in stratum basale, determines skin color
Melanocytes
protects keratinocyte DNA from mutations induced by UV radiation
Melanin synthesis
increases with exposure to natural or artificial UV radiation, lead to tanning
Tanning
darkening of skin pigmentation
Freckle
small area of increased pigmentation, increased melanin production in local spot
Mole
area od increased pigmentation, caused by local proliferation of melanocytes, not an increase in melanin production
Albinism
lack of melanin, results in a lack of skin pigmentation and a greatly increased risk of keratinocyte DNA damage from UV radiation
Accessory structures or appendages
include hair, nails, and glands, derived from epithelium only, assist in overall function of system
Hair (pili)
small filamentous structures, protrude from surface of skin over entire body except in regions with thick skin, lips, and parts of external genitalia
Hair structure
composed of 2 main parts, made of stratified squamous keratinized epithelial cells
Shaft
portion of hair projecting from skins surface, made of columns of dead keratinized epithelial cells
Root
segment of hair embedded in dermis
Hair papilla
indented at base by blood vessels from dermis
Hair bulb
root and hair papilla
Matrix
small number of keratinocytes at base of root , actively divide
Hair follicle
the root is embedded in this, infolding of epidermis extents deep into dermis
Inner medulla
soft core, only found in thick hair (head), soft keratin
Middle Cortex
keratinocytes containing hard keratin, provides strength
Outermost cuticle
overlapping keratinocytes containing hard keratin, provides strength
Dermal root sheath
surrounds epithelial root, consists of connective tissue
Arrector Pili muscles
small bonds of smooth muscle, contraction causes hair to stand up gives skin dimpled appearance, "goosebumps"
Nails
hard accessory structures at the ends of digits, composed of stratified squamous epithelium filled with hard keratin
Nail Plate
most visible component of nail, on top of underlying epidermal nail bed, divided into nail body and nail root
Nail body
visible portion of nail plate
Nail root
portion of plate under the skin, location of nail matrix containing actively dividing cells
Lunula
half-moon shaped region of proximal nail plate
Glands
two basic types in skin, derived from epidermal cells, deeper in dermis
Sweat (sudoriferous) glands
produce sweat
Sebaceous glands
produce oily sebum
Eccrine
type of sweat gland, most prevalent, simple coiled tubular glands in dermis, sweat contains mostly water, waste products, and electrolytes, exists from duct through sweat pore onto epidermal surface
Apocrine
found in specific regions of the body such as axillae, large glands release protein-rich secretion into hair follicles, secretions become odoriferous once skin bacteria metabolize contents
Ceruminous
modified apocrine glands, release thick secretion called cerumen (ear wax) into hair follicles in ear
Cerumen
ear wax
Mammary glands
highly specialized sweat glands, produce modified sweat (milk)
Sebaceous glands cout.
branched with clusters of secretory cells (acini) surrounded by small ducts, converge to form a central duct that empties into hair follicle
Sebum
waxy, oily mixture of mostly lipids
Acini
secretory cells