Dermatology Flashcards
What are the key functions of the skin?
Barrier to infection Thermoregulation Protection against trauma Protection against UV Vitamin D synthesis Regulate H2O loss
Where does normal proliferation of the skin ovvur?
In the basal layer
What is desquamation?
Shedding of mature corneocytes from the skins surface to balance the introduction of new cells.
What is the pH of the skin?
5.5
What causes desquamation?
Degradation of the extracellular corneo-desmosomes under the action of protease enzymes
What are the 3 main layers of the skin?
Epidermis (top layer
Dermis
Hypodermis (Subcutaneous fat)
What does the epidermis consist of?
Layers of keratinocytes undergoing terminal maturation.
Non-keratinocyte cells: Melanocytes, Langerhans cells, Merkel cells
What is the stratium corneum and what does it consist of?
The outermost part of the epidermis.
Made up of corneo-desmosomes (adhesion molecules) and desmosomes which keep the corneocytes together (brick and iron rod model)
What are corneocytes?
Terminally differentiated keratinocytes that compose most of the stratum corneum.
What is the action of melanocytes?
Responsible for melanin production and pigment formation
What is the action of Langerhans cells?
Antigen-presenting dendritic cells
What is the action of Merkel cells?
Sensory mechanoreceptors.
What is cornification?
Differentiation of keratinocytes into corneocytes (dead cells) to create a physical barrier for the skin.
What are the layers of the epidermis?
Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
How long does a keratinocyte typically take to travel from the stratum basale to the stratum corneum of the epidermis?
30-40 days
What are the layers of the dermis?
The superficial papillary layer and the deeper reticular layer
What are the features of the reticular layer of the dermis?
Thick with thick bundles of collagen fibres that provide more durability.
What structures are present in the dermis?
Fibroblasts Mast cells Blood vessels Cutaneous sensory cells Skin appendages
What are the actions of fibroblasts in the dermis?
Synthesise the extracellular matrix
What are the different types of skin appendages?
Hair follicles
Nails
Sebaceous and sweat glands.
Where are the skin appendages derived from and where do they present?
Derived from the epidermis and descend into the dermis during development.
What are holocrine secretions?
Mode of secretion by exocrine glands: Secretions are produced in the cytoplasm and released by the rupture of the plasma membrane which destroys the cell and releases the product into the lumen.
What is the hypodermis?
The tissue immediately deep to the dermis that is major body store of adipose tissue.
What are Meissner’s corpuscles and where are they?
Mechanoreceptors that can sense light touch.
Found in upper dermis