Derm - general Flashcards
Where does epidermis and dermis originate from?
Ectoderm
Mesoderm
White waxy protective substance secreted by?
Vernix caseosa secreted by periderm
4 strata proximal to distal?
Spinosum
Granulosum
Lucidum
Corneum
Which stratum is only found on palms and soles?
Lucidum
Where do melanoblasts originate from and what do they mature to?
Neural crest
Melanocytes
What regulates melamine?
Melanocortin 1 receptor
How is MC1R controlled? Agonists and antagonist
a melanocyte stimulating hormone
Adenocorticotrophic hormone
(Agonists) - synthesis of eumelanin & up regulation of mc1r gene
Agouti signalling protein (antagonist)
- pheomelanin production
How does UV exposure increase melanin content? (2)
Increased MITF experession and melanogenic proteins → increase in melanin
Increased PAR2 in keratinocytes → increased uptake and distribution of melanosomes
What cells make up epidermis and where do they divide?
Keratinocytes in basal layer
How long does it take keratinocytes to migrate from basal layer to surface?
30 days
What keratinocytes cytoskeleton consist of? (3)
Actin microfilaments
Tubulin microtubules
Keratin filaments
5 roles of keratins?
Structural Cell signalling Stress response Apoptosis Wound healing
Function of desomsomes? (4)
Adhesion complex
Anchor keratin to cell membrane
Bridge adjacent keratinocytes
Allow cells to withstand trauma
Function of gap junctions?
Connect cytoplasm of adjacent keratinocytes
Cell synchtonization, differentiation, growth and metabolic coordination
What are gap junctions?
Intercellular channels, connexons
Function of adherens junctions?
Engage actin skeleton , transmembrane
Function of tight junctions?
Barrier integrity
Cell polarity
Structure and function of melanocytes?
Dendritic
Distribute melanin to keratinocytes
Granules containing melanin?
Melanosomes
Structure, function and location of langerhans cells?
Dendritic
APC
Epidermis
Function of merkel cells?
Mechanosensory receptors
Cells found in epidermis? (5j
Keratinocytes Melanocytes Langerhans cells Merkel cells Mast cells
Structure and function of basement membrane? (Dermal epidermal junction)
Collagens 4 & 7
Laminin
Integrins
Cell adhesion and migration
2 types of dermis?
Papillary - superficial, loose, vascular
Reticular - deep, dense, bulk of dermis
Proteins found in dermis?
Collagen types 1 & 3
Fibrilln & elastin
Glycoproteins (3) in dermis and their function?
Fibronectin, fibulin, integrins
Cell adhesion and motility
Ground substance in dermis?
Between dermis collagens and elastic tissue
Glycosaminoglycan and proteoglycan
Primary cells of dermis.
Fibroblasts
Other dermis cells? (5)
Histiocytes Mast cells Neutrophils Lympocytes Dermal dendritic cells
Blood supply of skin and it’s location?
Superficial and depp vascular plexus
Dermis only
2 types of inner action of skin?
Sensory
Autonomic
Where are afferent nerves found and how are they distributed
In superficial dermis
More in face, extremities and genitalia than rest of body
2 types of afferent nerves and their receptors?
Corpuscular - encapsulated
Free - non encapsulated
Where are corpuscular encapsulated nerves found? Examples
Dermis
Pacinian
Meissmers
Where are free non-encapsulated nerves found? Examples
Epidermis
Merkel cell
Meissmers corpuscles - structure , location , distribution, function
Encapsulated , unmyelinated , lamellated capsule
Superficial dermis
Thick hairless skin eg lips and finger tips
Mechanoreceptors - light touch and low frequency vibration
Ruffin I corpuscles - structure , location , distribution, function
Spindle shaped
Deep dermis
Fingernails
Mechanoreceptor - skin stretch and object slippage
Pacinian corpuscles - structure , location , distribution, function
Encapsulated , ovoid
Dermal papillae of hands and feet
Phasic mechanoreceptor - deep pressure and vibration (surface texture)
Merkel cells - structure , location , distribution, function
Non-encapsulated, ovoid
Directly above basement membrane
Fingertips, palms, soles, genitalia, oral
Mechanoreceptor - light sustained pressure
6 functions of the skin?
Immunological barrier Physical barrier Thermoregulation Sensation Metabolism Aesthetic appearance
Immune cells of skin?
Langerhans cells in epidermis
How do langerhans cells sense environment?
Dendritic process extend through intercellular tight junctions
→ can sample stratum corneum
What do langerhans cells do in resting state?
Promote expansion and activation of Tregs
What happens when langerhans cell encounter antigen?
Innate response initiated
Cells mature and migrate to activate T cells → adaptive immune response
Immune cells in dermis? (3)
Tissue resident T cells
Macrophages
Dendritic cells
Purpose of immune cells in dermis?
Rapid backup if epidermis is breached
2 keratinocyte-derived endogenous antibiotics?
Defensins
Cathelcidins
Innate immunity
Function of stratum corneum as a physical barrier?
Restricts water and protein loss from skin
Skins role as a UV barrier?
Melanin I’m basal keratinocytes protects against UV DNA damage
Role of subcutaneous fat?
Cushions trauma
Calorie reserve
Release leptin hormone
How does the skin act as a thermoregulator?
Vasoconstriction and vasodilation in deep and superficial vascular plexuses
Eccrine sweat glands → cooling
What is the function of leptin?
Acts on hypothalamus to regulate hunger and energy metabolism
What vitamin does skin make?
D
6 functions of the hair?
Protection against external factors Sebum Approcrine sweat Thermoregulation Social and sexual interaction Epithelial and melanocytes stem cells
Two types of hair and location?
Terminal hair - scalp, eyelashes and eyebrows
Vellum hair - rest of body
There steps of hair cycle? (ACT)
Anagen , growth, most hair, 2-6 yrs
Catagen , regression, least hair, 3 weeks
Telogen , resting , 3 months
Describe structure of hair follicle?
Pilosebaceous unit
Pocket of epithelium continuous with superficial epidermis
Small papila of dermis at base
Where does arrector pili attach?
Surface of dermis and point of follicle wall
Name of gland associated with follicle?
Sebaceous glands
Open into piliary canal
2 divisions of hair follicle and location?
Infundibulum from sebaceous gland to skin surface
Isthmus from arrector pili,uncle to sebaceous gland
Type of epithelial keratinisation in hair follicle?
Trichilemmal keratinisation
Where do hair follicle stem cells reside?
Bulge of outer root level of arrector pili
2 ways in which hair stem cells migrate?
Downward- to generate lower anagen hair follicle in matrix → terminal differentiation to form hair shaft and inner root sheath
Upward - form sebaceous glands , proliferation in response to wounds
What does the bulb consist of?
Follicular dermal papila and hair matrix (lowest portion)
Function and location of outer root sheath?
From hair bulb to infundibulum
Stem cell reservoir
Function of inner root sheath?
Guides and shapes hair
5 functions of the nails?
Protect distal phalanx Counter pressure effect → walking and tactile sensation Increases dexterity Sensory discrimination Sractching/grooming
Structure of nail plate?
From nail matrix keratinocytes
From proximal nail fold to hyponychium
Attaches to nail bed
Lined with lateral nail folds
Function, cells and location of nail matrix?
Produces nail plate
Under proximal nail fold above distal phalanx
Differentiated keratinocytes and some melanocytes
Lunula = visible part
Explain the differentiation of nail matrix keratinocytes
Lose their nuclei
Become adherent
Cytoplasm completely filled with hard keratins
What is the difference between eccrine and apocrine glands?
Eccrine glands are found over most of the body and open directly onto surface of skin
Apocrine glands open into hair follicles, found on scalp, armpits, groin
In which stratum do keratinocytes lack nuclei and organelles?
Stratum corneum
Where are vascular plexuses found?
Dermis
