Dermatopathology Flashcards
Name Epithelial cells and layers
Cuboidal=Specialise in secretion and transport (sweat glands)
Columnar=Specialise in secretion (colon)
Squamous=Specialise in protection (some have keratin for extra protection)
Single layer (simple)
Many layers (stratified)
What are the components of skin and why?
Skin:
Hair
Sweat glands
Oil glands
(skin sits on top of muscle which sits on top of bone)
Why?
Sweat glands keep you cool
Hair for retaining warmth
Oil glands for no reason other than to ruin you day
The basics and terminology
“Derm” = something to do with skin, e.g.: dermatitis, epidermis
Epidermis = outermost layer of skin
Dermis = layer under the epidermis
Subcutaneous tissue = fatty tissue supporting the skin
sebaceous glands produce oils
The epidermis
Stratum comeum=Consists of many layers of keratinized dead cells that are flattened and non-nucleated; comified
Stratum lucidum=A thin, clear layer found only in the epidermis of the lips, palms, and soles
Stratum granulosum= Composed of one or more layers of granular cells that contain fibers of keratin and shriveled nuclei
Stratum spinosum= composed of several layers of cells with centrally located large, oval nuclei and spine like processes. Limited mitosis
Stratum basale= Consists of a single layer of cuboidal cells in contact with the basement membrane that undergo mitosis; contains pigment-producingmelanocytes,
TL:DR As the cell moves upward –> more keratin present, less nucleus until cornified
Keratinocyte maturation
Basal layer: (Stratum basale)
Single layer of columnar-like keratinocytes attached to the basement membrane
-Cells adhere to each other by connections at the desmosomes
-Mitotically active (but slow) with stem cell population present
Migration of cell from basal layer to stratum corneum takes 14 days.
-Takes another 14 days to progress all the way through the stratum corneum.
In hyperproliferative skin can be up to 2-3 cells thick
The epidermis
Squamous cell layer ( Stratum corneum)
-5-10 cells thick
-Basal melanocytes
-Langerhans cells very common
Granular layer (Stratum granulosum)
-Flattened cells with abundant cytoplasmic
-keratinohyaline
-Lipid component discharged - barrier
Cornified layer (Stratum spinosum)
-Cells = +++protein, low lipid
-Continuous extracellular lipid matrix
-Dead – no nuclei
Mechanical protection
Barrier to water loss
Barrier to invasion
Non-keratinoncyte cells of the epidermis
Melanocyte= Dendritic, protein synthesising cell (melanin)
Derived from neural crest, largely confined to basal layer
Merkel Cells=Oval shaped, slow adapting Type 1 mechanoreceptor. Found in digits, lips, oral cavity, outer root sheath of the hair follicle
Langerhans Cells= Dendritic cell eliciting a variety of T-cell responses.Found mainly in squamous and granular layers
The dermis
Eccrine sweat glands
Apocrine sweat glands
Apoeccrine sweat glands
Hair follicles
Sebaceous glands
Vasculature
Nerves
Muscle and fat
There is a basement membrane layer between the dermis and the epidermis. This helps stops cancer forming and spreading to the dermis. Lets cells move in and out and fluid exchange.
Thin upper layer – papillary dermis
Connective tissue
Vasculature (supply epidermis)
Thick lower layer – reticular dermis
Vasculature
Hair follicles
Oil & sweat glands
Nervous system
Sweat glands
Sweat glands:
Eccrine – most prominent on soles of feet, least plentiful on back
Primary role in thermoregulation
Neural control - hypothallamus
Apocrine – scent release, open into pilosebaceous follicle
Apoeccrine – similar to eccrine but found in axillae.
Sweat solution:
sodium (0.9 gram/liter)
potassium (0.2 g/l)
calcium (0.015 g/l)
magnesium (0.0013 g/l)
Trace lactic acid, urea
Hair
Hair bulb
Papilla
Sebaceous gland
Sweat gland
Arrector pilli muscle
Distribution of sweat products over skin surface
Sebum:
Glycerides: 30-50%
Fatty acids (sapienic acid): 15-30%
Waxes (wax esters): 26-30%
Cholesterol: 1.5-2.5%
Squalene: 12-20%
Prevent drying, waterproofs & antimicrobial
The skin in sensation
Merkel cell
Basal layer of epidermis
Light touch and sustained pressure
Meissner’s corpuscles
Hairless skin (dermal papillae)
Changes in light touch and vibration
Pacinian corpuscles
Large nerve-end organs (deep dermis)
Pressure and vibration changes
Ruffini receptors
Skin stretch and joint position sense
Heat
Free nerve endings
Pain, heat, cold, chemical injury
Itch (poorly understood - ? parasites)
(these are going down deeper into the dermis layer)
Skin circulatory system
Angiosome:
Composite block of tissue supplied by underlying arterial flow and drained by venous flow
Direct and indirect perfusion in the skin
Direct: Destined specifically for the skin
Indirect: Secondary branches of vessels supplying other tissues
Skin circulatory system - thermoregulation
Series of shunts and plexi enable a readily redistributable supply under local, neural and humoral control.
The main thermoregulatory role of thermal cutaneous signals is to provide negative and positive auxiliary feedback to the thermoregulation system.
Biomechanical properties of skin
Viscoelastic response – compression –> stretch to do with Elasticity of solids and Viscosity of fluid
Key vocabulary
describe a;
Macule
Cyst
Nodule
Bulla
Patch
Papule
Plaque
Pustule
Ulcer
Scale
Vesicle
Macule =<5mm area different colour to surrounding skin
Cyst= closed cavity/sac containing fluid or semi-solid
Nodule=usually >5mm firm, well-defined lesion
Bulla=>5mm area, raised fluid-filled blister
Patch = >5mm area different colour to surrounding skin
Papule= <5mm area discrete solid elevation
Plaque= >5mm area, palpable, discrete, solid, elevated body
Pustule= <5mm area, circumscribed elevation containing pus
Ulcer= circumscribed skin loss extending into dermis
Scale= regions of excessive stratum corneum
Vesicle= <5mm area, raised fluid-filled blister
