Flashcards in Skin Structure and Function Deck (60)
What are the 2 main layers of skin?
The epidermis (outer) and the dermis
Which germ layer is the epidermis derived from?
How does the epidermis form in the fetus?
Ectoderm cells form a single layer periderm which gradually increase in layers and before birth the periderm cells are cast off
What germ layer is the dermis derived from?
What are melanocytes derived from?
the neural crest
What are the 6 layers in skin?
Prickle cell layer
what are blaschkos lines?
developmental growth patterns of skin, which don't follow vessels, nerves or lympathics
What does the skin consist of?
epidermis; appendages (hair, nails, glands, mucosae) ; dermo-epidermal junction; dermis and the sub-cutis
What does the basal layer do?
Divides in order to replenish the upper layers
How does the prickle cell layer become the granular layer?
It differentiates and produces lots of protein (granular- lots of proteins)
How does the granular layer becoem the keratin layer?
Releases protein in order to become flat
What type of epithelium is the epidermis
stratified squamous epithelium
What are the majority of the cells found in the epidermis?
Keratinocytes which contain structural keratins
What other cells are found within the epidermis?
Melanocytes; langerhan cells and merkel cells
How is epidermal turnover regulated?
growth factors; cell death and hormones
How long does it take for a keratinocytes to migrates from the basmement membrane to the top?
Describe the basal layer
usually one cell thick
lots of intermediate filaments (keratin)
highly metabolically active
Describe the prickle cell layer
larger polyhedral cells
lots of desmosomes
intermediate filaments connect to desmosomes
(named after prickly pear appearance)
Describe the granular layer
2-3 layers of flatter cells
large keratohyalin granules- contain structural filaggrin and involucrin proteins
odland bodies ( lamellar bodies)
high lipid content
origin of "cornified envelope"
cell nuclei lost
What is the cornified envelope?
A layer of ceramides which become covalently bonded to an envelope of structural proteins. This replaces the cell membrane during a process called cornification in which live keratinocytes become non-living corneocytes. The complex surrounds the cells and contributes to the barrier function of the skin.
Describe the keratin layer
Made up of the corneocytes- overlapping non-nucleated cell remnants
insoluble cornified envelope
80% keratin and filagrin
lamellar granuels release lipid
TIGHT WATRETPROOF BARRIER
What are melanocytes?
pigment producing dendritic cells
Where are melanocytes found?
in the basal layer and above
What happens in the melanosomes?
tyrosine is converted to melanin pigment
What happens to full melanosomes (melanin granules)?
they are transferred to adjacent keratinocyte via dendrites
What is the function of melanin granules?
form a protective cap over nucleus as they absorb light and prevent UV ray messing with the DNA in basal cells
What is vitiligo?
an autoimmune disease where there is loss of melanocytes
What is the origin of langerhan cells?
mesenchymal origin (bone marrow)
Where are Langerhan cells found in the skin?
prickle cell level in the epidermis and in dermis (also in lymph nodes)