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What are epidermal dendritic cells ?
They ingest foreign substances and are key activators for our immune system
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What tactile (Merkel) cells?
function as a sensory receptor for touch
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Where is the stratum basale layer located?
the deepest epidermal layer
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Why is stratum basale also called stratum germinativum?
the mitotic nuclei seen is this layer reflect rapid division of these cells
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What is the stratum spinosum (prickly layer) made of?
weblike system of intermediate filaments mainly pre-keratin tension-resisting filaments
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Stratum Granulosm (granular layer)
- consists of three to five cell layers
- keratinazation begins (cells fill with the protein keratin) cells flatten nuclei and organelles degin
- to disintergate accumulate two types of granules
- keratohyaline granules- help to form keratin in the upper layers
- lamellated granules- contain a water resistant glycolipid that is spewed into the extracellular space and a major factor slowing water loss across the membrane
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Stratum Lucidum ( Clear Layer)
- thin translucent band just above the stratum granulosum
- two to three rows of clear, flat,dead keratinocytes with indistinct boundaries
- visible only in thick skin
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Stratum Corneum
- outermost layer 20-30 cell layers thick
- keratin and the thickened plasma membrane of cells in this stratum protects the skin against abrasion and penetration
- protects the deep layers from the external hostile environment
- shingle-like cell remnants are referred to cornified (dandruff)
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Dermis
- second major skin layer, contains fibroblasts, macrophages, mast cells, and white blood cells
- richly supplied with nerve fibers, blood vessels, and lymphatic vessels
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Papillary ( Dermis)
- areolar connective tissue fine collagen and elastic fibers interlaced with blood vessel
- its superior surface is thrown into peglike projections called dermal papillae that indent the overlying epidermis
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Recticular ( Dermis)
- accounts for 80% of the thickness of the dermis, coarse irregularly arranged dense connective tissue(fibrous)
- cutaneous plexus lies between this layer and the hypodermis
- cleavage lines and flexure lines
flexure lines are dermal folds that occur or near joints where the dermis is tightly secured (wrists, finger and toes, palms, and soles)
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Melanin
- a polymer made of tyrosine amino acids
- color range yellow to tan and reddish-brown to black
- melanocytes are stimulated to greater activity by chemicals secreted by the surrounding
- keratinocytes when we expose our skin to sunlight
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Carotene
- yellow to orange pigment
- accumulates in the stratum corneum and its fatty tissue of the hypodermis
- found in the palms and soles
- converted to vitamin A
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Sweat glands (sudoriferous)
- distributed over the entire skin surface
- eccrine glands- far more numerous and are particularly abundant on the palms, sole of the feet
- coiled tubular gland, secretory pile lies in the dermis, and the duct opens to the skin surface
- Appocrine sweat glands- 2000 found in the axillary and the anogenital area
- release their product exocytosis lie deeper in the dermis and hypodermis
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Sebaceous (oil) glands
- simple avelolar branched glands that are all over body except the palms and soles
- secrete sebum- accumulate oil lipids until they burst holocrine glands
- lubricates the hair prevent from being brittle
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