Intro To Dermatology Flashcards
What does epidermis originate from
Ectoderm
What does dermis originate from
Mesoderm which induces differentiation of epidermal structures
Superficial strata of epidermis from superficial to deep
Corn Luvers Grow Several Gereens)
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum germinativum basal layer
Which layer is only on palms of hands and soles of feet
Stratum lucidum
Which layer has granules of keratohyalin
Stratum granulosum
State which layer has no nuclei or organelles
Stratum corneum
State which layer is joined by desmosomes?
Stratum germinativum → Stratum spinosum → Stratum granulosum → Stratum lucidum (found on palms of hands and soles of feet) → Stratum corneum
Structure of skin in order of layers from epidermis to subcutaneous fat
Epidermis
Basement membrane
Dermis
Subcutaneous fat
What is epidermis composed of
MMMLK
Keratinocytes
Melanocytes
Langerhan cells
Markel cells
Mast cells
What junctions connect keratinocytes
- Tight junctionsRole in barrier integrity and cell polarity
- Adherens junctions- what do they do?Transmembrane structures which engage with actin skeletonFROM POM: master junction that controls formation of all the others
- Desmosomes- what do they do (detail)?anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes to allow them to withstand trauma
- Gap junctions-
Allow cell synchronization,differentiation,cell growth and metabolic coordination
Function of different parts of corneum
- Top layer absorbs solutes
- Middle layer absorbs water to keep skin hydrated
- Bottom layer is a mechanical defence barrier and includes lipids like sterols and fatty acids that are important for this function
How long do cells take to go from the basement membrane to top?
30 days and this is accelerated in skin disease
Melanocytes
dendritic cells which distribute melanin pigment (in melanosomes) to keratinocytes
Same number in different skin types
Langerhans cells
Dendritic cells (have finger like-processes) and are APCs
Merkel cells
Mechanosensory receptors
Basement membrane (dermal-epidermal junction)- what does this structure consist of and what are its (2) roles
- Made up of proteins and glycoproteins like collagens (IV, VII), laminin and integrins
- Roles are cell adhesion and cell migration (esp of immune cells)
Dermis layers
- Papillary dermis- superficial, loose connective tissue, vascular
- Reticular dermis- deep, dense connective tissue, forms bulk of dermis
Which 3 substances make up the dermis?
- Proteins- 80% collagen (mainly I and III), 3% elastic fibres- fibrillin and elastin
- Glycoproteins- fibronectin, fibulin, integrins- facilitate cell adhesion and motility
- Ground substance- between dermal collagen and elastic tissue- glycosaminoglycans and proteoglycans- maintain hydration of dermis due to high water binding capacity of hyaluronic acid (60% of dermis weight is water)
What is the main cell present in the dermis and also which (5) other cells are present?
Fibroblasts
Histiocytes, mast cells, neutrophils, lymphocytes and dermal dendritic cells.
What is the blood supply to the skin like, and does it cross into the epidermis
- Deep and superficial vascular plexus
- Doesn’t cross into epidermis
What is the innervation to the skin like?
- Sensory- free nerve endings, hair follicles and expanded tips- 1 mil afferent nerve fibres that form branching network in superficial dermis often accompanying blood vessels
- Distribution varies by body site e.g. face, extremities and genitalia are more richly innervated than rest of skin
Describe the two autonomic innervations to sweat glands?
- Cholinergic innervation, which sweat gland does it innervate?eccrine sweat glands (salty water non smelling sweat)
-
Adrenergic innervation, which (2) sweat glands does it innervate?
Eccrine and apocrine
What is another term for a hair follicle, and which muscle erects the hair?
pilosebaceous unit
arrector pili muscle (within hair follicle along with arterioles)
What 2 types of afferent nerve are there (+ what receptor types do they end in and in which layer of the skin are they found)?
- Free ended that end in non-encapsulated receptors in epidermis like Merkel cell
- Corpuscular that end in encapsulated receptors in dermis like Pacinian, Meissners
What are Meissner’s corpuscles (aka tactile corpuscles)? (what do they detect and where are they most concentrated?)
- Encapsulated, unmyelinated mechanoreceptors in dermal papilla
- Lamellated capsule
- Most concentrated in thick hairless skin e.g. finger pads and lips
- Detect light touch and slow vibration- low frequency stimulation
What are Ruffini corpuscles (aka Bulbous corpuscles)? (what is their shape like, what do they detect, what is their receptor speed like, & in which body parts are they concentrated) SSS)?
- Slow acting mechanoreceptors deeper in dermis
- Spindle-shaped
- Sensitive to skin stretch (stretch sensitive/detect stretch)
- Highest density around fingernails- monitor slippage of objects
What are Pacinian corpuscles (aka lamellar corpuscles)? (what do they detect (3 things), what is their receptor speed like, what is their shape like)
- Encapsulated, ovoid shaped, rapidly adapting (phasic) mechanoreceptors (fast)
- Detect deep pressure and vibration (deep touch)
- ovoid shape
- Also detects surface texture
- Dermal papillae of hands and feet
What are Merkel cells? (what do they detect, what is their shape like, where in the epidermis are they found, and in which body parts are they concentrated? )
- Non-encapsulated mechanoreceptors (are modified keratinocytes)
- Detect light/sustained touch, pressure
- Oval-shaped
- Found in stratum basale
- Most populous in fingertips, also found in palms, soles, oral and genital mucosa
Which (4) bacteria predominates in the microbiome of the skin?
Predominantly Actinobacteria, Firmicutes, Bacteroidetes, and Proteobacteria
Skin microbiomes
- Microbiota- bacteria (1 mil/cm^2 of skin), fungi and viruses
- Predominantly actinobacteria, firmicutes (clostridia and bacilli (staphylococcus)), bacteroidetes, proteobacteria
- Composition of each niche depends on environment on different parts of body
- Role in immune-modulation and epithelial health
Function of skin
Immunological barrier
Physical barrier
Thermoregulation
Metabolism
Appearance
Sensation
Langerhans cells- what do they do?
- Tissue-resident T cells, macrophages and dendritic cells also carry out immune surveillance in dermis to give rapid, effective immunological backup if epidermis is breached
-
Keratinocytes make their own endogenous antibiotics (defensins and cathelicidins)- part of innate immune defence
Toll like receptorsagainst bacteria, viruses etc and fungi
Sense environment
When toll like receptors detect danger via PAMP rapid initiation of innate anti microbial responses
Physically Barrier
- Physical barrier to external environment
- UV barrier
- What does the cornified cell envelope and stratum corneum do?restrict water and protein loss from skin
- What has an important role in cushioning trauma?Subcutaneous fat
- What protects us against UV-induced DNA damage
Melanin
Thermoregulation
- Vasodilation or vasoconstriction in deep or superficial vascular plexuses regulate heat loss
- Eccrine sweat glands give an evaporative cooling effect
Metabolism
- Vitamin D synthesis- conversion of 7-dehydrocholesterol into cholecalciferol
- Subcutaneous fat has calorie reserves- 80% of total body fat in non obese people is subcutaneous
- Which hormone released from subcutaneous fat acts on hypothalamus to regulate hunger and energy metabolism?
Leptin release
Aesthetic appearance
- Psychosexual function
- Increased risk of suicide with people with skin conditions
Describe the effects of an inflammatory skin disease/erythroderma:
Any rash covering >90% of body
You get skin failure and the above functions are compromised
You’re susceptible to infection, lose water transepithelially (can cause kidney failure), impaired thermoregulation so can get heart failure
Hair
Terminal hairs found on scalp eyebrows and eyelashes
Rest of body has vellus hairs
Hair cycle
Anagen-where hair grows. 85% of hair is in this stage
Catagen-Hair follicle begins to shrink. Regressing phase lasts 3 weeks. 1% of hair
Telogen-resting phase
Asts three months old hair then lost
Structure of hair
Infundubulum is the uppermost portion of the hair follicle
Isthmus is the lower portion of the upper part of hair follicle. Epithelium keratinization begins here with lack of granular layer called trichilemmal layer
Nail plate
Is the final product of proliferation and differentiation of nail matrix. Emerges from proximal nail fold and detaches at hyponychium
What extends dendritic processes through intercellular tight junctions to the stratum corneum
Langherhans cells
In absence of danger what do langerhan cells do
Promote expansion and activation of skin resident regulatory cells
Eccrine sweat glands
Almost everywhere on skin
Open directly onto skin surface
Apocrine sweat glands
Open into hair follicle
In areas with many hair follicles such as scalp armpits and groin
Nail matrix
Produces nail plate
Lies under proximal nail fold above bone of distal phalanx
