primarily axilla, anus, and external genitalia, associated with hair follicles, wide lumen, merocrine secretion, innervation is sympathetic adrenergic (NE)
apocrine sweat glands
induces neural crest
intermediate concentration BMP4
contain filaggrin and other intermediate filament-associated proteins such as keratin filaments (tonofilaments). Help aggregate tonofilaments into tonofibrils
melanin granule transport
via kinesin or dynein along microtubules, keratinocytes phagocytose melanocyte processes to take up melanin granules. Kensin in cytoplasmic extension, dynein in keratinocyte.
skin pigmentation related to...
rate of melanin degradation AND ratio of keratinocytes to melanocytes
antigen-presenting immune cells of the skin and mucosa, and contain large granules called Birbeck granules. They are present in all layers of the epidermis, but are most prominent in the stratum spinosum.
Langerhan’s cells - indented nucleus
single cell layer, adjacent to basal lamina, cuboidal to low columnar cells, vitamin D production, stem cells (mitotically active), extensive cell junctions, desmosomes, hemidesmosomes. Life span of 2 months.
stratum basale (stratum germinativum)
columnar shape, produce sweat, increased mitochondria and glycogen, adjacent to intercellular canaliculi
clear (C) cells
darker than spinosum. one to three cell layers thick, squamous cells, retain nuclei, keratohyalin granules
expression induces dermatome development
epidermal germinative zone for nail
dermis for limbs and body wall
lateral plate mesoderm
layers of epidermis
stratum corneum (with deep stratum lucidum in thick skin), stratum granulosum, stratum spinosum (prickle cell layer), stratum basale (stratum germinativum)
rapid proliferation shortens transit time from basal cell to desquamation time to about 7 days
types of sweat glands
accrine and apocrine
keratinocytes cell junctions
hemidesmosomes tether keratinocytes of stratum basale to basal lamina. Focal adhesion interacting with actin cells also tethering SB to BL.
secretory product released into duct with cell debris after apoptosis
holocrine secretion - Example: sebaceous glands of integument
protection, vitamin D production, immunologic function, sensation, thermoregulation
Skin lines that become apparent with some diseases of the skin. The lines are believed to trace the migration of embryonic cells.
lines of Blaschko
high concentration BMP4
face and neck dermis
neural crest cells
tactlile sensation, neural crest derived,
Merkel’s cells - located in stratum basale, abundant in fingertips, synapse with pseudounipolar neurons and tethered to keratinocytes by desmosomes.
dermatome cells express
noggin, chordin, and follistatin
expression by the notochord inhibits BMP4, which allows ectoderm to form neural plate
are small, nipple-like extensions (or interdigitations) of the dermis into the epidermis.
from dermatome (dermis) drives differentiation. expressed in early embryonic phases in paraxial mesoderm, which it helps to demarcate.
dense irregular connective tissue, less cellular, closely packed fiber bundles, thick collagen fibers (I), thick elastic fibers
correlation between sebum amount and acne
thick epidermis that secures free edge of nail
induces neural plate (CNS)
low concentration BMP4
secretory product released from apical end of cell into duct, takes with it some cytoplasm and plasma membrane.
apocrine secretion - Example - lactating mammary glands.
deep pressure, vibration
keratinized cortex cells contain
epidermis epithelial type
keratinized stratified squamous epithelium
keratinocytes water barrier
formed by lamellar bodies
a type of nerve ending in the skin that is responsible for sensitivity to touch.
Meissner’s corpuscle, Ruffini’s corpuscle, Merkel's Cell
merocrine secretion, innervation is sympathetic cholinergic (ACh), sweat and antibacterial glycoprotein granules, narrow lumen in duct.
eccrine sweat glands
internalize and degrade HIV-1, Langerin induces formation.
induce ectoderm to form epidermis
BMP4 and FGF
collagen and elastic fibers oriented in parallel lines
Langer’s lines - surgical incisions parallel to Langer’s lines heal faster
free nerve ending
pain, temperature, tactile
variable thickness of layer, squamous cells, anucleate, keratinized cells (soft keratin)
stratum corneum (with deep stratum lucidum in thick skin)
no desmosomes, production of melanin granules,
melanocytes, neural crest derived. Migrate to stratum basale, PAX3 from dermatome (dermis) drives differentiation, melanin granules migrate out toward cytoplasmic extensions.
accumulation of keratohyalin granules (KG) as cells differentiate from BL to surface, highest concentration of KG in stratum granulosum.
Asymmetrical shape of lesion, Border of lesion is irregular, Color variations, Diameter greater than 6 mm.
loose connective tissue, more cellular, lots of ground substance, loosely arranged fibers, thin collagen fibers (I, III), thin elastic fibers
lipid product plus cell debris after apoptosis
cytoplasmic protein structures made of keratinin that converge at desmosomes and hemidesmosomes. Also associated with desmosomes (macula adherens), anchoring them to the cytoskeleton.
8 layers of hair follicle
outer to inner: hair papilla, connective tissue, glassy membrane (basal lamina), external and internal root sheath, cuticle, cortex and medulla (innermost)
a result of proteolytic degradation of desmosomes in a pH dependent manner
pyramidal shape, antibacterial glycoprotein granules, increased RER and Golgi, adjacent to lumen
dark (D) cells
A layer of the epidermis found between the stratum granulosum and stratum basale. Spiny (Latin, spinosum) appearance is due to shrinking of the microfilaments between desmosomal that occurs when stained with H&E. Keratinization beginshere.
wound healing mechanism
stratum basale ramps up mitosis, migration of proliferating cells, exfoliation of dead keratinocytes frees scab, fibroblasts differentiate into myofibroblasts (directed by TGF-b1), myofibroblasts involved in wound closure
branched acinar gland that uses holocrine secretino to secrete sebum.
hair follicles, sebaceous glands, sweat glands
nodes of Bizzozero
desmosomes in the stratum spinosum of epidermis
secretory product released from apical end of cell via exocytosis into duct.
merocrine secretion - example - sweat glands of integument.
secrete (exocytosis) pro-barrier lipids, lipid processing enzymes, and proteases into intercellular space between stratum granulosum and stratum corneum