Skin Flashcards
Skin Primary Layers (3)
Epidermis
Dermis
Hypodermis
Epidermis (4)
Stratified barrier
Mostly keratinocytes (cells which produce keratin protein - in hair)
Avascular
Constant shedding
Dermis
Protein fibres for strength
Vascular (nourishes epidermis)
Hypodermis
Adipose tissue (fat stored & can be used for insulation OR feeding the body)
Common injection sites using hypodermic needles
Layers of Dermis
Papillary Layer - collagen & elastin fibres (for strength)
Reticular Layer - blood vessels & connective tissue supporting skin (hair follicles & sweat/oil glands found here)
Shapes of Epithelial (3)
Squamous (flat/squashed) - main type
Cuboidal (cubes)
Columnar (tall columns)
Epidermis Layers (CGSB)
Stratum Corneum (dead; shedded)
Stratum Granulosum (dries cells + waxy material for water-tight barrier in intercellular spaces)
Stratum Spinosum (skin flexibility)
Stratum Basale (columnar regenerative cells; basal cell divides = daughter cells become keratin which migrates up to replenish layer above)
- Desmosome
- Hemidesmosome
- Anchors cells together preventing things passing through (found throughout epidermis)
- Only found in basal layer to anchor it to dermis layer
Thick Skin Layers (CLGSB)
Come
stratum Lucidum = another layer of protection)
Get
Some
Burgers
e.g., palms, feet soles (no hair)
Cutaneous Plexus
Blood vessels present at epidermis/dermis junction
Supplies hypodermis, deeper dermis including capillaries for hair follicles & sweat glands
Subpapillary Plexus
Branches from cutaneous plexus; lies deep to papillary layer of dermis
Blood vessels providing oxygen & nutrients to upper dermis & epidermis
First-Degree Burn (4)
Superficial (outer layers of epidermis)
Erythema
Skin remains water/bacterial barrier
Heals 3-10 days
Normal Second-Degree Burn (3)
Epidermis & varying dermis amounts
Moist, erythema & blistered
Heal 1-2 weeks (needs good dressing)
Deeper Second-Degree Burn (4)
White-ish, waxy areas
Hair follicles & sweat glands may remain
Heal 1 month
May lose some sensation + scarring
Third-Degree Burn (4)
Extends into subcutaneous tissue & may involve muscle & bone
Could be waxy white + deep red/black
Hard, dry, leathery skin
Sensory nerve endings destroyed = sensation lost
May require skin grafting
Weeks/months to regenerate + scarring
Skin Accessory Structures (4)
Hair
Sweat Glands
Nails
Receptors
Hair
Made of dead, keratinised cells produced inside hair follicle
- Arrector Pili Muscle
- Root hair plexus
- Sebaceous glands
- Lanolin
- Contraction = goosebumps (insulation)
- Sensory nerves at follicle base (sensation)
- Sebum (oily) nourish hair & moisturise skin; blocked follicles + infection (too much sebum) = acne
- Sheep sebum in skin care products
Eccrine
Most areas of skin
secretes onto skin (important for thermoregulation & excretion)
Some antibacterial action
Apocrine (3)
Specific areas (armpit, groin, around nipple)
Secrete sticky/oily & sometimes odorous into follicle base
Influenced by hormones e.g., lactation
Nails (3)
Protect fingertips/toes
Enhance sensation
Sensory receptors require deformation (deformation limited by nail; avoid injury)
Skin Aging (4)
Degrading collagen
Degrading elastin (loose skin)
Slower Healing
Less sebum (drier epidermis)
Smoking (4)
Damages collagen & elastin
Poor wound healing
Acne
Skin & oral cancer
Melanocytes
Cell which produces/contains pigment melanin
Only found in Stratum basale
Melanosomes
Found throughout epidermis (shed w/ keratinocytes)
Vesicles containing melanin (transfers melanin to epidermal cells)
Mole
Cluster of melanocytes (over-proliferation can be due to sun exposure)
Vitamin D
UV exposure required for vitamin D synthesis
Essential for normal Ca2+ metabolism & strong bones
Basal Cell Carcinoma (3)
Common but relatively gentle
Originates in stratum basale
Spread is rare
Malignant Melanoma (3)
Rare but deadly
Originates in melanocytes
Highly spreadable
Tattoo
Placed on dermal layer
Captured in immune cells/scar tissue
Melanin
Absorbs UV light (protects cells from UV damage)
Freckle
Melanocytes overproducing melanosomes (over-production triggered by sun exposure)
Sebum is an oily secretion produced by _______
Sebaceous glands
Melanocytes found in the ____
Stratum basale
Moles are caused due to over-proliferation of _____
Melanocytes
Two types of sweat glands are _____ & _______
Eccrine & Apocrine
Free Nerve Endings (4)
- mostly unmyelinated small diameter fibres
- usually small swellings at sensory terminals
- responds to various stimuli (temp, noci-, movement/pressure)
- activation leads to AP in axon sending signals to CNS
Receptor Types (5)
Free nerve endings
Tactile discs
Tactile corpuscles
Lamella corpuscles
Bulbous corpuscles
Tactile Discs (4)
- FNE in deepest epidermis layer
- Abundant in fingertips & small receptive fields; good for 2-pt discriminated
- Fine touch & light pressure
- texture, shape & edges
Tactile Corpuscles (5)
- in papillary layer of dermis
- branching unmyelinated sensory terminals surrounded by Schwann & thin oval FCT capsule
- Capsule deformation = Na+ enters terminal = AP
- sensitive to shape/textural changes (fine/discriminative touch)
- low fqncy vibration & light pressure
Lamella Corpuscles (7)
- scattered deep in dermis & hypodermis
- single dendrite lying in concentric layers of collagen fibres & specialised fibroblasts
- layers separated by gelatinous interstitial fluid
- capsule deformation = pressure sensitive Na+ channels open in sensory axon
- inner layers covering axon terminal relax quickly = rapid adaption as AP discontinues
- deep pressure (when first applied)
- vibration (due to rapid adaptation)
Bulbous Corpuscles (7)
- in dermis & subcutaneous tissue
- network of nerve endings mixed w/ core of collagen fibres that are continuous w/ surrounded dermis; capsule surrounds entire structure
- important for signalling continuous states of deformation of tissue like heavy prolonged touch & pressure signals
- also found in joint capsules where help signal degree of joint rotation
- in fingers can help to modulate grip
- sustained deep pressure
- stretching/distortion of skin
How is skin temp regulated?
Via vasoconstriction/dilation of blood vessels occurring via smooth muscle in vessel & precapillary sphincters controlled by SNS (fight/flight)
Vasoconstriction
reduced blood flow (conserve heat)
Vasodilation
increase blood flow (get rid of excess heat)
Noradrenaline (hormone)
reduce skin blood flow by acting on alpha-1 adrenergic receptors found in smooth muscle of vessels which activate 2nd mssngr path to increase Ca2+ in cell leading to vasoconstriction = decreased blood flow
Decreasing activation of alpha-1 receptors…
Causes vasodilation = increased blood flow
Structure/Function Eccrine Sweat Glands (3)
- innervated by sympathetic cholinergic fibres
- AcH released onto g-protein coupled receptors (GPCR) known as mAChRs causing sweating
- some glands also stimulated by adrenaline on to B-receptors (i.e., nervous sweating)
Eccrine Role in Thermoregulation
- there’s heat loss/gain centres in hypothalamus
- when temp rises above set pt, heat loss centre activates THUS cholinergic activation of mAChRs increases on eccrine –> sweating
Mechanisms of Heat Transfer (4)
Conduction = direct contact
Convection = constant heat transfer via air, water etc
Radiation = heat transfer via infared rays
Evaporation = heat loss via energy used in water evaporation (e.g., sweating)
