This Dermatology study guide will provide you will a clear understanding of the cause, diagnosis and management of common, and less common, dermatological pathologies. This will assist you in your fourth and final year medical school exams.
Understand structure and function of skin
Terminology of skin lesions and describing them
Dermatological treatments
Aetiology, pathology, clinical features, investigation and treatment of common
skin conditions.
The role of the dermatologists.
Surgery techniques
Dermatological history
Structure and function of the skin and psoriasis
1. Epidermis structure
(Keratinocytes, Langerhans cells and melanocytes)
Langerhans cells are the skin’s specialised dendritic cells that are immune-
surveillance to present antigens further down the immune system.
Melanocytes are the pigmented cells in the epidermis that protect against UV.
Stratum corneum. Made up of corneocytes with intracellular lipids secreted
from lamellar bodies. Differentiate into corneocytes as move up the epidermis,
with the loss of nuclei, aggregation of keratin into kerato-hyaline granules
which are then cross link with cell envelope to make them insoluble.
Granular layer (stratum granulosum)
Suprabasal layer (Stratum spinosum) K1 (basic) and K10 (acidic)
Basal layer (stratum basale) K5 (basic) and K14 (acidic)
Stratum lucidum (In areas where the skin is thicker i.e. sole)
, Functions of the skin
Epidermis
Protection against injury and wear and tear. This is by continual renewal of
the epidermis. When the skin is injured, the stratum basale will divide to cover
the wound initially. Over time the cells with differentiate in the normal
mechanism and ascend in this process to fill in each layer of epidermis.
o As cells move up through the epidermis the keratin content increases
from 35 to 80% (protective)
Impermeability to passage of chemicals, water (the skin is waterproof),
electrolytes, microbes and UV radiation.
Melanocytes in the stratum basale produce melanin pigment which migrate
into the keratinocytes. The number of melanocytes are similar across different
pigmentary groups, but the rate of production varies due to UV stimulation.
Nucleotide excision repair of UVR-DNA damage (unwind, excise, repair) Skin
cancer occurs when the DNA repairing function of the skin becomes
exhausted.
Cancer of Keratinocytes (BCC or SCC). Cancer of Melanocyte
(melanoma)
Antimicrobial properties (Langerhans cells part of innate immune response.
They migrate out of the epidermis and into the dermis to the lymph vessels in
order to activate the immune system)
Dermis
Collagen in the skin also protects against injury as well at keratinocytes. The
epidermis connects to the dermis through structures called hemidesmosomes.
The hemidesmosomes connect keratins 5 (basic) and 14 (acidic) to the
stratum lucidum and the type VII collagen in the dermis. (hemidesmosomes
are similar to desmosomes but desmosomes connect only adjacent cells)
Thermoregulation. The dermis contains all the blood supply of the skin. The
dermal papilla at the top of the dermis give a large surface area for
thermoexchange. Superficial plexus and middle plexus of blood vessels. This
is for vascular heat exchange and sweating.
Endocrine (Vitamin D production)
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