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.
What are the rete ridges?
Downward invagination of the epidermis in the dermis. It creates a larger SA for adhesion.
What are the dermal papillae?
Upward projections of the dermis into the epidermis for adhesion between the layers. It contains mechanoreceptors called Macinian corpuscles for light touch and low frequency vibration.
What are the layers of the dermis?
Papillary dermis
Reticular dermis
What is the papillary dermis?
Highly vascularised layer formed of loose connective tissue which contains the rete ridges and the dermal papillae. Contains an extensive lymphatic network and nerve endings. Fibroblasts are contained here which secrete components for collagen and elastin.
Which collagen type is found in the dermis?
Type 1 and 3.
What is the reticular dermis?
Formed of dense connective tissue containing the skin appendages and sweat glands.
What are the eccrine sweat glands?
Coiled tubular glands which produce sweat containing NaCl for thermoregulation, found in the reticular dermis.
It uses merocrine secretion which is exocytosis of contents.
What are the apocrine sweat glands?
Large coiled tubular glands that become functional during puberty produce viscous rich sweat responsible for body odour. Typically found near the breast and axillary.
It uses apocrine secretion, losing part of its cyptoplasm as it discharges the fluid into the uppper part of the hair follicle.
Which immunoglobulin is found in the skin?
IgE.
