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stratum[stra´tum, strat´um] (L.)
stratum basa´le the deepest layer of the epidermis, composed of a single layer of basophilic cells. Called also basal layer of epidermis.
stratum cor´neum the outer horny layer of the epidermis, consisting of cells that are dead and desquamating. Called also horny layer.
2. the lower layer of the nail, from which the nail grows; called also germinative layer.
stratum granulo´sum the cell layer of the epidermis lying between the stratum lucidum and the stratum spinosum. Called also granular layer.
1. the deep layer of the cortex of the cerebellum.
2. the layer of follicle cells lining the theca of the vesicular ovarian follicle; called also granular layer.
stratum lu´cidum the clear translucent layer of the epidermis, just beneath the stratum corneum. Called also clear layer.
one of the layers of the epidermis, situated just below the stratum corneum except in the thick skin of the palms of the hands and the soles of the feet, where it lies just under the stratum lucidum. The stratum granulosum contains visible granules in the cytoplasm of its cells, which die, become keratinized, move to the surface, and flake away. Compare stratum basale, stratum corneum, stratum lucidum, stratum spinosum. See also skin.
stratum granulosum; stratum malpighii enzymically active, partly keratinized cells; forms the suprabasal epidermal layer, between stratum spinosum and stratum corneum Table 1
|Epidermis||Stratified squamous epithelium formed from keratinocytes|
Basal layer: keratinocytes linked by desmosomal and hemidesmosomal and filamentous connections (cytoskeleton; prevents shear)
Spinous layer: keratinocytes shrink, retaining contact only at desmosomes and hemidesmosomes
Granular layer: keratinocytes secrete complex lipids which act as a semipermeable skin barrier
Corneal layer: cell and contents have become keratin to form squames moved towards the exterior
Melanocytes: lie between keratinocytes; secrete pigment and protect keratinocyte nuclei from ultraviolet radiation
Merkel cells: sensory cells
Langerhans cells: within spinous layer; antigen-presenting cells
|Basement membrane zone||Collagen, hemidesmosomes, laminin which aid adhesion of epidermis to dermis; dysfunctional in disease such as epidermolysis bullosa|
|Dermis||Mesodermal tissue containing blood vessels, nerve, muscle, skin appendages (sweat glands, sebaceous glands, hair follicles), immune cells (histamine-releasing mast cells) in a matrix of collagen, elastin and hyaluronic acid|
|Subcutaneous layer||Adipose tissue, blood vessels and nerves, acting as an insulating layer|
pl. strata [L.] a sheetlike mass of tissue of fairly uniform thickness; distinct layers making up various tissues or organs, as of the skin, brain, retina.
the avascular stratum in the margin of the iris.
the mitotically active, basal layer of the epidermis, consisting of columnar to cuboidal keratinocytes on a basement membrane.
the outer horny layer of the epidermis, consisting of cells that are non-nucleated, keratinized and desquamating.
in the epidermis, located between the stratum basale and the stratum granulosum. Together with the basal layer, called the malpighian layer. Called also germinative layer.
1. the layer of cells between the stratum lucidum and the stratum spinosum of the skin, very thin and not always present. Called also the granular layer.
2. the deep layer of the cortex of the cerebellum.
3. the layer of follicle cells lining the theca of the vesicular ovarian follicle. Called also granular layer.
laminae of the hoof corium.
the translucent layer of the skin just beneath the stratum corneum. Called also clear layer. Present in the epidermis of the planum nasale of several species and footpads of carnivores.
the layer of the epidermis between the stratum granulosum and the stratum basale, marked by the presence of prickle cells; called also spinous layer and prickle-cell layer.
the layer of horny scales claimed to exist on the surface of the horse's hoof that gives it the smooth glossy appearance.