Structure and function of the skin Flashcards
main layers of the skin
epidermis- oute
dermis- layer below epidermis
subcutis- - fat layer beneath dermis
type of epithelium epidermis
stratified squamous cellular epithelium
95& contain structural keratins
what is the dermis
connective tissue
what is the epidermis formed by
single layer periderm
what is the dermis formed from
mesoderm below ectodermw
what are melanocytes
pigment producing cells from neural crest
blaschkos lines
development growth pattern of skin
thought to represent pathways of cell migration during foetal development
what does the skin consist of
Epidermis
Dermo-epidermal junction
Dermis: connective tissue, less cellular
Appendages
Nails
Hair
Glands
Mucosae
Sub-cutis: predominantly fat
layers of epidermal cell layers
keratin layer
granular layer
prickle cell layer
basal layer
what is regulation of epidermal turnover controlled by
growth factors
cell death
hormones
what is there a loss of regulation of epidermal turnover in
skin cancer
psoriasis
where do keratinocytes migrate from
basement membrane
basal layer characteristics
usually one cell thick
small xuboidal
lots of intermediate filaments
highly metabolically active
prickle cell layer characteristics
larger polyhedral cells
lots of desmosomes
intermediate filaments connect to desmosomes
granular layer characteristics
2-3 layers of flatter cells
Large keratohyalin granules – contain structural filaggrin & involucrin proteins
Odland bodies (lamellar bodies) – secretory organelles that contribute to skin barrier
High lipid content
Origin of “cornified envelope”
Cell nuclei lost
keeratin layer characteristics
Corneocytes
overlapping non-nucleated cell remnants
Insoluble cornified envelope
80% keratin & filaggrin
Lamellar granules release lipid
Tight waterproof barrier
where do melanocytes migrate from
neural crest to epidermis in first 3 months of foetal development
melanocytes characterisitcs
basal layer and above
pigment producing dendritic cells
Contain organelles : ‘melanosomes’
Convert tyrosine to melanin pigment
Eumelanin (brown or black)
Phaeomelanin (red, yellow)
Melanin absorbs light (neutral density filter)
Full melanosomes (‘melanin granules’) transferred to adjacent keratinocyte via dendrites
Form protective cap over nucleus
black/ asian skin differences
larger melanosomes containing more melanin hpwever same number of melanocytes
more layers in keratin layer
More eumelanin + less phaeomelanin in dark skin
what is vitiligo
autoimmne disease with loss of melanocytes
langerhans cells characteristics
Mesenchymal origin – bone marrow
Prickle cell level in epidermis
Also found in dermis and lymph nodes
Involved in the skin immune system
Antigen presenting cells
Pick up antigen in skin and circulate to lymph nodes via lymphatic system
what are merkel cells
found in basal layer of epidermis
mechanoreceptors - help define touch and sensation
between keratinocytes and nerve fibres
mucosal membranes
occular mucosa- Lacrimal glands, eye lashes, sebaceous glands
oral mucosa - Masticatory – keratinised to deal with friction/pressure
Lining mucosa – non-keratinised
Specialised mucosa - tongue papillae – taste
