Structure and Function of skin Flashcards
The developmental growth pattern of skin follow which lines?
Blashcko’s lines (not following any nerves, vessels or lymphatics)
What are melanocytes and where do they migrate from?
Pigment producing cells from the neural crest.
95% of the epidermis is made up of what cells?
Keratinocytes, they contain structural keratins
What type of epithelium is the epidermis?
Stratified squamous
What are the 4 epidermal cell layers?
Basal Layer (Deep)
Prickle cell layer
Granular Layer
Keratin layer (Superficial)
What is meant by differentiation?
Keratinocytes migrating from the basement membrane, this takes 28 days. Continuously regenerates the epidermis.
Describe the basal layer
Usually one cell thick, small and cuboidal.
Lots of intermediate filaments (keratin)
Highly metabolically active.
Describe the prickle cell layer
Larger Polyhedral cells (think P for Prickle, P for Polyhedral)
Lots of desmosomes (connections)
Intermediate filaments connect to desmosomes
Describe the granular layer
2-3 layers of flatter cells Large keratohyalin granules – contain structural filaggrin & involucrin proteins Odland bodies (lamellar bodies) High lipid content Origin of “cornified envelope” Cell nuclei lost
Describe the keratin layer
Corneocytes (overlapping non-nucleated cell remnants) Insoluble cornified envelope 80% keratin & filaggrin Lamellar granules release lipid Tight waterproof barrier
Melanocytes
Migrate from the epidermis to neural crest in first 3 months of foetal development
basal layer and above
pigment producing dendritic cells
What is Nelson’s Syndrome?
A disorder where melanin stimulating hormone is produced in excess by the pituitary (resulting in far darker than expected skin)
What layer are Langerhan’s cells found?
Prickle cell layer in epidermis
What do langerhans cells do?
They are antigen presenting cells that pick up antigens in the skin and circulate them to the lymph nodes via the lymphatic system.
Phases of hair growth, what is anagen, catagen and telogen?
anagen = growing catagen = involuting telogen = resting
What is the dermo-epidermal junction?
It is an interface between the epidermis and dermis. It holds a key role in epithelial-meschymal interactions e.g.:
- support, anchorage, adhesion, growth and differentiation of epidermal cells.
- it is a semi permeable membrane that acts as a barrier and a filter.
Cells in the dermis:
Fibroblasts: secrete collagen
Macrophages: scavengers, antigen presentation
Lymphocytes: immune reactions
Langerhans cells (also in epidermis): antigen presentation
Mast cells: chemical messengers
What is the most important structure in the skin that determines drug penetrance?
Stratum corneum
Tuberous Sclerosis
- One of the most common genodermatoses
- May present as infantile seizures
- Earliest sign is the ash leaf macule
- Autosomal Dominant
- It is the next most common genodermatosis after NF type 1
- Depigmented macule found in 90% of tuberous sclerosis
- Other skin signs are shagreen patches and enamel pitting.
Epidermolysis Bullosa:
3 types: simple, junctional and dystrophic
- Dominant, recessive, new mutation or acquired.
- Variable severity - blistering at birth does not determine prognosis
Features of Neurofibromatosis Type 1:
Café au lait Neurofibromas Plexiform neuroma - diffuse Axillary or inguinal freckling Optic glioma 2 or more Lisch nodules A distinctive bony lesion
Eczema is a complex disease, describe some of the genetic factors:
Filaggrin (a skin barrier gene, mutations are common approx 1 in 10)
IL-4 and IL-13
Eczema Hepeticum
Monomorphic punched out lesions
