Biology Of The Skin Flashcards
What is the role of the skin?
Mechanical barrier to water and chemical. It is important for Vitamin D synthesis, temperature regulation and immune defence.
What are the layers of the skin?
Epidermis, dermis no subcutaneous layer.
What is the epidermis composed of?
Outer cornified layer and stratified squamous epithelia with melanocytes, keratinocytes, and Langerhans cells.
What are the layers of the epidermis?
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum Lucidum (only found in thick skin)
Stratum corneum
What is the stratum basale?
Single cuboidal cell layer of dividing keratinocyte stem cells, melanocytes and merkel cells on top of the basement membrane. Vitamin D synthesis occurs here and this is the only layer capable of cell division.
->Keratinocytes differentiate into tonofilaments which group into tonofibrils.
What is the stratum spinosum?
Contains irregularly shaped keratinocytes forming tonofilaments linked by desmosomes. Dendritic cells are found here for immune defence. Vitamin D synthesis only occurs in the stratum spinosum and basale.
What is the stratum granulosum?
Containing keratohyalin granules for aggregation of keratin filaments and lipid lamellar bodies for hydrophobic barrier.
What is the stratum corneum?
Formed of dead keratinocytes which have undergone apoptosis and lose nuclei and organelles. This forms a tough barrier which maintains hydration. The desmosomes are prone to breaking so desquamation occurs.
Where are the melanocytes located?
Stratum basale. They are dendritically-shaped cells which are responsible for skin pigmentation by synthesising melanin which is packaged into melanosomes for protection against UV damage.
How long does it take keratinocytes to restore the skin layers?
30 days which increase in keratin concentration as they develop. They migrate up the layers of the skin and lose their cellular architecture and undergo apoptosis in the corneum layer.
What are Langerhaan cells?
Antigen presenting cells in the epidermis of the skin for immune defence.
What are Merkel cells?
Mechanoreceptors found in the stratum basale for light touch sensation
Why does scaling occur?
Imbalance between skin renewal and loss.
Why do blisters occur?
Breakage of cell-cell junctions.
What is the composition of the epidermal-dermal junction?
Dermal papillae and rete ridges. They increase SA for adhesion between layers and increase vascularisation.