8 - Skin Flashcards
What are the 3 main layers of the skin? What are they composed of?
EPIDERMIS - composed of epithelial layers
DERMIS - composed of connective tissue
—> includes blood vessels, sweat glands etc
SUBCUTANEOUS TISSUE
NOTE: there is a basement membrane lying between the epidermis and the dermis, keeping the outside layer tightly connected (anchored) to the inside layer
Give the orders of the layers in the epidermis
- stratum corneum - corneocytes
- (stratum lucidium) - compressed/flat cells
- stratum granulosum - keratinisation begins
- stratum spinosum - ‘ prickle cells’, keratin production begins
- stratum basale - basal cells (most inner layers)
What are the cells of dendritic morphology in the epidermis?
Give their functions
MELANOCYTES
- produce melanin
- attach to the BM and form close associations with keratinocytes via dendrites
- helps to block UV damage to DNA in keratinocytes
LANGERHAN CELLS
- APCs
MERKEL CELLS
- involved in sensation
- the nerve endings in the skin - mechanoreceptors
What is the basement membrane (with reference to the skin)?
a specialised zone where the epidermis is attached to the dermis via hemidesmosomes, an anchoring plaque and a multitude of proteins
it lies between the epidermis and the dermis and holds them together
What are hemidesmosomes?
What is their function?
Hemidesmosomes are the adhesion units between the basal layer of the epidermis and the dermis.
Their main function is attachment but also control permeability across the dermis.
Give an associated clinical condition of the BM?
- epidermolysis bullosa - when proteins in the BM don’t work properly. This meanstrauma or friction to an area of skin could result in the epidermis and dermis becoming unstuck. If the two layers become separated, a space is created which fills with fluid to form ablister
- bulls pemphigoid - the immune system produces antibodies to the fibers that connect the epidermis and the dermis. These antibodies trigger inflammation that produces blisters and itching.
What is the dermis and what constitutes it?
supportive connective tissue
containing: collagen, elastin, GAGs, blood vessels, lymphatics, fibroblasts, immune cells, DCs
What comprises the subcutaneous fat layer?
connective tissue and fat
What type of cells are melanocytes and where are they located?
DCs
located within the basal layer of the epidermis
What function do melanocytes perform?
They produce melanin (a pigment) in melanosomes (a type of organelle)
Describe the production of melanin?
Occurs in melanosomes.
These are packaged into granules which move down the dendritic processes and transferred by phagocytosis to adjacent keratinocytes.
What is the action of melanin?
The melanin granules form a protective cap around the keratinocyte nuclei and protect the DNA from UV induced damage and lead to skin pigmentation.
At what lengths of UV radiation does stimulation of melanocytes to produce melanin occur?
290-320 nm
What causes the variation in racial pigmentation?
the number and size of melanosomes produced
not the differences in melanocyte numbers
