Skin Flashcards
What are the components of the integumentary system ?
- skin, hair, nails, some nerves and glands
What are the functions of the integumentary system ?
- shield/barrier to external environment
- regulates body temp
- touch/sensitivity
- retention of body fluids
- protects against disease & infection
What are Merkel cells ?
- specialist cells found in digits,lips, oral cavity & hair follicles
- stimulated when keratinocytes are deformed to secrete chemicals that generate an action potential in local neurons
Describe the general properties of the skin
- largest organ in the body
- forms a continuous layer with the mucous membranes which covers all the body’s surfaces
- contains specialised cells
- 3 layered = epidermis, dermis & subcutaneous adipose layer
Describe the epidermis
- superficial layer of the skin
- made of epithelial cells
- has no vascular system
-contains specialised epithelial cells which are organised in a stratified structure
Describe the stratified structure of the epidermis
- cornified cell layer
- granular layer
- squamous epithelial tissue
- basal layer
- basement membrane
Describe the Cornified Cell layer of the epidermis
- stratum corneum
- keratinocytes terminal differentiate to corneocytes and provide a barrier to the external environment
- stops excessive water loss
Describe Corneocytes
- filled with keratin
- no nucleus
- keratinised layer stops water loss from inside & stops penetration of water from outside
Describe the granular cell layer of the epidermis
- 1-3 cells thick
- stratum granulosum
- keratinocytes in this layer contain lots of keratohyline granules in cytoplasm –> key players in keratinisation
- eventual terminal differentiation removes organelles from cells
Describe the squamous cell layer
- stratum spinosum
- 5-10 cells thick
- keratinocytes take on a flattened shape - appear squamous and become flatter as they travel to the top layer
- contain lamellar granules which contain hydrolytic enzymes
- keratin fibres formed around the nuclei
Describe the basal cell layer of the epidermis
- stratum basale
- where keratinocytes begin their journey & proliferate
- keratinocytes appear column shaped & attached to basement membrane
- long elongated uncle & support squamous cells
What are Melanocytes
- pigment synthesising cells
- found in the epidermis, iris & hair
- responsible for melanin production & its transportation to keratinocytes via melanosome
- 1 melanocyte communicates with 30/40 keratinocytes in an epidermal melanin unit
Describe how melanocytes and keratinocytes interact to defend against UV damage
- pigment globules are released from the melanocyte dendrites into the extracellular space
- the globules are captured by microvilli of the keratinocytes
- they’re transported via a protease activated receptor 2 (PAR-2) dependent mechanism
- the membrane of pigment globule is degraded
- single melanosomes are released into a keratinocyte cytosol & move into the perinuclear space
- UV protection is offered to cells nucleus by the melanosome
Describe Langerhans cells
- immune cells involved in T cell responses
- found in all layers of the epidermis - most abundant in the squamous cell layer
- during infection Langerhans cells act as 1st responders to pathogens
Describe the Dermis
- contains extracellular matrix & collagen
- fibroblasts produce collagen & other proteins which give skin its flexibility & structure
- thickest layer
- contains fibrous, filamentous & amorphous connective tissue
- made of 2 layers = papillary & reticular layers
Describe the Papillary Dermis
- uppermost layer of the dermis
- joined to the basal membrane of the epidermis
- contains loosely arranged collagen fibres
- papillae (finger-like projections) that extend towards the epidermis contain capillaries & Meissners Corpuslcles
Describe the reticular dermis
- lower layer of dermis
- consists of dense connective tissue - densely packed collagen & elastic fibres
- contains roots of hair, sebaceous glands & sweat glands
Describe Dermal Fibroblasts
- most abundant cell in the dermis
- responsible for the production of key matrix proteins - fibrillin, elastin & collagen
- quantity & quality declines in ageing skin
Describe Subcutaneous Adipose tissue
- helps with thermoregulation
- stores energy for use when necessary
- contains adipocytes
- controls some hormones
What are the 2 types of aged skin?
- chronically aged skin
- photo aged skin
Describe Chronically Aged Skin
Thin, dry & finely wrinkled
Describe Photoaged Skin
leathery,
lax ,
deep wrinkles
uneven pigmentation
Telangiectasia
Lentigines
What is telangiectasia ?
broken looking visible blood visible
What is lentigines ?
age spots
Describe the reduced function in ageing skin
- slower wound healing response
- loss of elasticity
- reduced collagen I
- reduced overall collagen
- reduction of epidermal hyaluronic acid
What are some theories of skin ageing ?
- oxidative stress
- UV radiation
- Mitochondrial dysfunction
- cellular senescence
How do physical sunscreen work?
- UVA & UVB are blocked from entering skin by an impenetrable layer of minerals on the skins surface
- active ingredient is titanium dioxide or zinc oxide
How does chemical suncream work ?
- usual mode of action is for active ingredients to convert UV rays into heat
- active ingredients = avobenzone, octinoxate & oxybenzone
Describe Trans Epidermal Water Loss
- when water passes from the dermis through to the epidermis & evaporated from the surface of the skin
- causes dry skin
What are the 3 types moisturiser ?
- occlusives
- emollients
- humectants
Describe Occlusives
- acts as barrier ontop of stratum corneum
- stops water molecules escaping
- long acting typically
- strengthens lipid framework of stratum corneum
Describe Emollients
- Penetrates the stratum corneum (cornified cell layer)
- emollient particles fill up the spaces between corneocytes
Describe Humectants
- Enters the cornified cell layer & attracts moisture from the environment & retains it inside the layer
What are the 4 stages of wound healing?
- Hemostasis
- Inflammatory
- Proliferation
- Remodelling
Describe Hemostasis
Blood clot forms & bleeding is halted
Describe the inflammatory stage of wound healing
- infiltration by macrophages/Langerhans cells to the wound site to fight any bacteria
- fibroblasts produce extracellular matrix
Describe the proliferation stage of the wound healing process
- fibroblasts proliferate & epithelial cells start to cover the wound
Describe the Remodelling of the wound healing process
the cell of the dermis & epidermis re-organise to reduce scarring
Describe 1st Degree Burns
- only affects the epidermis
- wound is red & dry with no blisters
- typically superficial
Describe 2nd Degree burns
- affects the epidermis & some of the dermis
- blisters & redness
- may be swollen & painful (painful thickness)
Describe 3rd Degree burns
- destroys the epidermis & dermis
- may go to the underlying subcutaneous tissue
- burn site may look white, charred or blackened
Describe 4th Degree Burns
- burn involves all 3 layers of the skin
- can also include muscle & bone
- no pain is felt due to nerve damage
Describe Basal Cell Carcinoma
- 80% of cancer is BBC
- Effects basal epithelial cells at the base of epidermis
- mostly found on sun exposed areas
- rarely progresses to metastasize
Describe Squamous Cell Carcinoma
- 2nd most common type of skin cancer
- involves the squamous cell layer
- mostly found in sun exposed areas
- more invasive than BCC
Describe Melanoma
- effects pigment cells = melanocytes
- more aggressive than BCC & SCC
- can effects parts of the body not exposed to the sun
- can metastasize to brain, liver & lungs
Describe Merkel Cell Carcinoma
- relatively rare but aggressive
- more common in sun exposed areas
- more likely to occur in people over 50’s & compromised immune systems
- can metastasize
Describe Psoriasis
- immune mediated condition that results in the build-up of skin cells on the surface of the skin & the addition of inflammatory response
What are some examples of Psoriasis ?
- scalp psoriasis
- nail psoriasis
- plaque psoriasis
Describe Eczema
- altered barrier function
- immune cell responses & hypersensitivity
- this reduces in increased water loss, pH alteration, skin dehydration, itching, scratching & risk of infection/ inflamed skin
