Skin Flashcards
(42 cards)
Epidermis type and origin
It is an epithelial layer of ectodermal origin
Dermis type and origin
It is connective tissue of mesodermal origin
Skin appendages
Sweat glands
Sebaceous glands
Hair
Nails
Types of skin
Thick skin
This skin
Epidermis cell types
It is formed of Stratified squamous keratinized epithelium
Has keratinocytes and non-keratinocytes
Keratinocytes are:
Arranged in 5 layers Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
Stratum basale
Germinal layer
Single layer of columnar cells
Cytoplasm is basophilic due to high ribosomal content
Many mitotic figures
EM:
Contains IF (tonofilaments)
There are desmosomes between cells and hemidesmosomes at the basment membrane
Stratum spinosum
Prickle cell layer
Several layers of polygonal cells with central nuclei
Some mitotic figures
Has many spinous interdigitating processes and intercellular bridges ending with desmosome
Many tonofilaments in the cytoplasm
Stratum granulosum
Granular layer
3-5 layers of polygonal cells with central nuclei
The cytoplasm contains basophilic non-membranous granules called keratohyaline granules
EM:
There are membrane coated lamellar granules that reease lipid-containing substance in the intercellular space. This forms a barrier against invasion with foreign materials resembling intercellular cement
Stratum lucidum
Clear layer
It is translucent thin layer of eosinophilic flattened cells containing eledin
EM:
Cells have no organelles, no nuclei and the cytoplasm is mainly formed of closely packed tonofilaments embedded in an electron dense matrix
desmosomes are still present
Stratum corneum
Horny layer
Superficial cells are shed
Consists of many layers of flattened non-nucleated keratinized cells
Cytoplasm is filled with filamentous scleroprotein called keratin
Malpighian layer
Stratum basale + stratum spinosum
Renewal occurs every 15-30 days
Non-keratinocytes examples
- Melanocytes
- Langerhan’s cells
- Merkel’s cells
Melanocytes origin
Derived from the neural crest
Ectodermal
Melanocytes
Sites
Between cells of stratum basale and in hair follicles
Melanocytes
LM
They have rounded cell bodies with central nuclei
They long cytoplasmic processes extend between cells of Malpighian layer
Melanocytes
EM
Cytoplasm contains numerous smal mitochondria, well-developed Golgi and rER
Not attatched to keratinocytes by bind to the basal lamina by hemidesmosomes
Epidermal-melanin unit
One melanocyte maintains an association with a given number of keratinocytes
Epidermal-melanin unit
One melanocyte maintains an association with a given number of keratinocytes
Function of melanin
Fuse with lysosomes and occupy a supranuclear position protecting the dividing nucleus from UV rays
Albinisim
Genitic defect in tyrosinase enzyme so no melanin is produced
Melanocytes are DOPA +ve or -ve
DOPA +ve
Keratinocytes are DOPA +ve or -ve
DOPA -ve
Melanophages/Melanophore cells are DOPA +ve or -ve
DOPA -ve
