skin Flashcards
stratified squamous epithilum is composed mainly of?
cells called keratinocytes
melanin is _____ abundant in thick skin
less
what are the 3 sections of skin?
-layers of skin, specialized cells & dermal structures and appendages
in Thick skin, what is the hydrophobic lipid envelope called?
S. Granulosum
In Thick skin, what layer has a translucent appearance?
S. Lucidum
In Thick Skin, what layer does keratinization begin?
S. Spinosum
In Thick skin, in what layer are stem cells located?
S. basale
what is the deepest layer in the skin?
Stratum Basale
what stimulates mitosis in S. Basale
molecules from underlying dermis like keratinocyte growth factor, fibroblast growth factor
what inhibits mitosis in S. Basale?
Inhibited by retinoic acid; retinoic acid increases the rate of cell differentiation leading to a thinner skin
Which layer is directly connected to basement membrane?
Stratum Basale
which structures directly attach cells to the basement membrane?
Hemidesmosomes
what is the term used to describe a defect in the anchoring of epidermis and dermis
Epidermolysis Bullosa
Where are “Spiny cells” found?
S. Spinosum
Where are Keratohyaline granules found?
S. Granulosum
what are Keratohyaline granules?
they form dense cytoplasmic granules that promote dehydration of the cell as well as aggregation and cross-linking of the keratin fibers
what precursor is held in keratohyaline granules
aggregations of high basophilic protein precursor called profilaggrin
- filaggrin corsslinks keratin
When are phosphate groups removed from profilaggrin?
AFTER it is cleaved into Filaggrin; prior to this it is highly phosphorylated
What are the “waterproofing” structures? where are they found?
Lamellar Bodies found in Stratum Granulosum; lipid-rich secretion is expelled from lamellar bodis that helps waterproof the skin
what helps to stabilize the cell membrane of the dead keratinocyte? Where is it synthesized?
Involucrin; synthesized in Stratum spinosum
What are melanocytes?
melanin producing cells found in the basal layer of skin
What happens to melanosomes?
they are produced by melanocytes and are phagocytized by kerationcytes
how do melanocytes protect DNA
melanin produced absorbs UV light to prevent damage to DNA
where are melanosomes degraded?
they are degraded in the upper layers of skin by lysosomes
what happens to MSH after exposure to UV light?
MSH is induced by UV light; increase in mRNA
What are Langerhans cells? where are they found?
dendritic cells (antigen-presenting immune cells) containing large granules called Birbeck granules. They are found in all layers but most prominent in S. Spinosum. They actively migrate between keratinocytes to exit the epidermis and reach lymph nodes
What are Birbeck granules
endosomes specialized for phagocytosis
what are Merkel cells?
oval receptor cells associate with the sense of light touch; determination of shapes and textures. found in the basal layer
what are Eccrine Sweat Glands?
major Sweat Glands of the body; found in virtually all skin; highest density in palms and soles
what is the purpose of myoepithelial cells
they contract and expel the secretions of exocrine glands
What are the layers that make up Eccrine sweat gland?
Dark cells, clear cells, and myoepithelial cells
what is the purpose of dark cells?
they secrete an antibacterial protin called DERMICIDIN
What is the purpose of clear cells?
they transposrt Na, Cl and H2O towards the lumen
describe the pathway of the transport of sweat
carried from eccrine glands into the epidermis; transported in a spiraling cavity between keratinocytes that terminates upon the surface.
Where are apocrine sweat glands found?
found only in certain locations of the body: the Axillae (armpit), areola and nipples of the breast, ear canal, eyelids and some part of the external genitalia
What happens to the secretory material of Apocrine cells?
transformed into pheromones.
what are sebaceous glands? where are they found?
they are exocrine glands, with holocrine mode of secretion, that secrete an oily or way substance called sebum. Found in the greatest number on the face and scalp; not on palms of the hands and soles of the feet
what is the purpose of sebum
to lubricate and waterproof the skin
how to sebaceous glands die?
via apoptosis and burst, releasing lipids into the hair follicle
What are found in the epidermis?
S. Croneum S. Granulosum S. Spinosum S. Basale keratinocytes langerhans cells Melanocytes
What is found in the dermis?
reticular and papilary layers
what is found in the hypodermis?
epidermal appendages: hair sebaceous glands, apocrine sweat glands, eccrine sweat glands, pacinian corpuscles and Meissner’s corpuscles
