Skin and Function Part 1 Flashcards
What is the epidermis?
Outer layer of skin, stratified cellular epithelium
What is the dermis?
Layer beneath the epidermis, connective tissue
What is the epidermis formed from embryonically?
Ectoderm-form a single layer periderm, gradual increase in layers of cells, periderm cells cast off
What is the dermis formed from embryonically?
Mesoderm
What are melanocytes?
Pigment producing cells from neural crests
What is gastrulation and when does it occur?
Cellular organisation into germ layers; occurs days 7-10
What does the skin look like at 4 weeks?
Periderm on top of basal layer, both sit atop dermis (corium)
What does the skin look like at 16 weeks?
Keratin layer (top layer), then granular layer then prickle cell layer, finally basal layer atop of dermis, melanocytes migrate from neural crest
What does the skin look like at 26 weeks?
Epidermis has formed, melanocytes have appeared as well as sebaceous glands, arector pili muscle and hair follicles
What are Blaschko’s lines?
Developmental growth pattern of skin caused by mutations within cells, not following vessels/nerves/lymphocytes, normal development up until 18 weeks
What is the other name for Blaschko’s lines?
Epidermal nevis
What does skin consist of?
Epidermis, appendages, dermo-epidermal junction, dermis, sub-cutis (predominantly fat)
What are the four layers of the epidermis, starting from the most superficial?
keratin layer, granular layer, prickle cell layer, basal layer
What are other cells found in the epidermis?
Melanocytes, Langerhans cells, Merkel cells
What is 95% of the epidermis made from?
Keratinocytes (contain structural keratins)
How thick is the epidermis?
1.5 mm
How are prickle cells connected?
Via little spikes (desmosomes) which vibrate and allow them to move upwards
What is epidermal turnover and how is it controlled?
Balance of cells in/out; controlled by growth factors, cell death and hormones
What can result from a loss of control of epidermal turnover?
Skin cancer and psoriasis
How long does it take for the epidermis to fully regenerate?
28 days from bottom to top
What are some features of the basal layer?
Usually one cell thick, small cuboidal cells, lots of intermediate filaments (keratin), stem cells so highly metabolically active
What are some features of the prickle cell layer?
Larger polyhedral cells, lots of desmosomes, intermediate filaments connect to desmosomes
What are some features of the granular layer?
2-3 layers of flatter cells, large keratohyalin granules, Odland bodies, high lipid content, cell nuclei loss
What do keratohyalin granules contain?
Structural filaggrin and involucrin proteins
How does eczema arise?
The granular area is deficient in filaggrin so people can’t conserve water
What are corneocytes?
Overlapping non-nucleated cell remnants
What do lamellar bodies release in the keratin layer?
Lipids
Why does HPV occur?
Keratinocytes become infected due to deficient skin barrier
What are some features of the keratin layer?
Insoluble cornified envelope, tight waterproof barrier, 80% keratin and filaggrin, has corneocytes
Where does the cornified envelope originate from?
The granular layer
Where are areas that mucosal membranes are found?
Eyes, mouth, nose, genito-urinary and GI tract
What are some specialised forms of oral mucosa?
Masticatory (keratinised to deal with friction/pressure), lining (non-keratinised), specialised (tongue papillae)
What are some features of ocular mucosa?
Lacrimal glands, eye lashes, sebaceous glands
