Exam 2 Flashcards
order of epidermis layers
stratum basale, stratum spinosum, stratum granulosum, stratum lucidum (in thick skin), stratum corneum
order of dermis layers
papillary layer, reticular layer
keratinocyte
major cell type of the epidermis
located in stratum basal and lower part of stratum spinous
keratinization
formation of tonofibrils, formation of keratohyalin granules, association of keratohyalin granule proteins with tonofibrils (stratum lucidum)
tonofilament
intermediate filament composed of keratin formed in the stratum basale
keratohyalin granules
basophilic aggregations of free polysomes that produce histidine-rich and cysteine-rich proteins, produced in the upper stratum spinous and stratum granulosum
soft keratin
combination of tonofibrils and the proteins of the keratohyalin granules
hard keratin
trichohyalin granules produced and monofilaments become more extensively cross-linked to amorphous keratin via disulfide bonds
membrane-coating granules (MCGs) aka lamellar bodies
Contribute a lipid bilayer to the epidermal water barrier
membrane-bound organelles first produced in the stratum spinosum
melanocyte
between cells of the stratum basale, derived from the neural crest
tyrosinase
enzyme that converts tyrosine into dopa and then dopaquinone (precursors of melanin)
Langerhans cell
pale-staining cell with elongated cell process of bone marrow origin function as antigen-presenting cell, can act as a viral reservoir that harbors AIDS, contain the Birbeck granule
Merkel cell
found on basement membrane, function as touch receptors in thick skin (finger tips, lips), slow to adapt
thick skin
has all five layers of the epidermis
found only on the palms of hands and the soles of the feet
is glabrous (hairless)
thin skin
has no stratum lucidum
is located on most parts of the body
is vellus (hairy)
papillary layer
superficial layer of the dermis, loose connective tissue, upper surface has dermal papillae, more connective tissue cells than reticular layer
reticular layer
deeper layer of the dermis, dense irregular connective tissue
Meissner’s corpuscles
encapsulated receptors formed by modified Schwann cells giving a layered or zigzag appearance, detect light touch
Pacinian corpuscles
encapsulated receptors that respond to deep touch or vibration, located in the deep dermis or hypodermis
hypodermis
not actually a part of skin, consists of loose connective tissue and adipose tissue that binds skin to underlying organs
glassy membrane
thick basement membrane that surrounds the hair follicle
external root sheath
composed of epithelial cells and is continuous with the epidermis
hair bulb
base of the follicle, matrix epithelial cells, also contains melanocytes
internal root sheath
lies between external root sheath and hair shaft, composed of keratinized epithelial cells
hair shaft
composed of hard keratin and three parts: medulla, cortex, and cuticle
Arrector pili muscle
bundle of smooth muscle attaches to skin and CT sheath outside the glassy membrane, contraction raises the hair shaft to a more vertical position and causes goose bumps
vellus hair
thin, short, poorly pigmented hair
terminal hair
thicker, longer and more heavily pigmented hair
anagen
period of active growth (when matrix cells divide)
catagen
period of involution when the lower part of the follicle below the arrestor pili muscle atrophies
telogen
resting period between the end of follicular atrophy and the shedding of the hair
sebaceous glands
acinar exocrine glands with a holocrine mode of secretion for sebum
eccrine sweat glands
simple coiled tubular exocrine glands with ducts that open directly onto skin surface and distributed over entire body except for lips and parts of external genitalia
secretory portion of eccrine sweat glands
psuedostratified cuboidal epithelia, lighter staining, located deep in the hypodermis, surrounded by myoepithelial cells
duct portion of eccrine sweat glands
lined by stratified cuboidal epithelium (2 layers), reabsorbs NaCl from the secretion to prevent excessive salt loss, no myoepithelial cells
apocrine sweat glands
coiled tubular exocrine glands found on axilla, areola, nipple, perianal region and external genitalia
secretory portion of apocrine sweat glands
wide lumen lined by simple epithelium surrounded by myoepithelial cell
duct portion of apocrine sweat glands
narrow duct lined by 2-3 layers of cuboidal cells
nail plate
hard portion of the nail
nail root
skin that covers proximal portion of the nail plate
nail matrix
proximal end of nail root with stem cells that nail plate grows
lunula
crescent-shape at the proximal end of the visible portion of the nail, partially keratinized cells
nail bed
made up of stratum basale and stratum spinous which are continuous with those layers surrounding the skin
eponychium
cuticle made of hard keratin
hyponychium
thickened epithelial layer that secures the free end of the nail plate to the fingertip
cyanosis
pale blue color of nail plate due to poor oxygenation in the circulating blood
split nails
indicative of nutritional deficiencies
clubbing
thickening of the nail base and wrapping of nail plate around the sides of the finger
spoon-shaped (concave) nails
indicative of iron deficiency anemia
psoriasis
increased rate of cellular proliferation resulting in accumulation of cells of the stratum corneum, producing pink-red areas with flakes or plaques
warts
benign epidermal growths caused by papilloma viral infection of keratinocytes
basal cell carcinoma
least deadly form involving cells of stratum basale usually due to excessive UV radiation, malignant cells rarely spread beyond skin (dermis or epidermis)
squamous cell carcinoma
can be deadly if spreads, involves cells of stratum spinosum, probably caused by radiation or chemical agents
malignant melanoma
involves melanocytes, rapidly dividing cells, invasive
