DERM WEEK 1 Flashcards
Which component of skin?
- outer layer
- stratified cellular epithelium
- contain keratinocytes (structural keratins)
- recieves movement from basement membrane
- contains four layers
epidermis
Which component of the skin?
- formed from mesoderm below ectoderm
- beneath epidermis
- made up of connective tissue
- less cellular
dermis
what cells produce pigment in the skin?
melanocytes
- from neural crest (transient embryonic structure that gives rise to most of the peripheral nervous system)
what three layers are formed at 4 weeks of foetal skin development?
- periderm
- basal layer
- dermis
what five layers are produced at 16 weeks? (final stage development)
- (from inner to outer)
- dermis
- basal layer
- prickle cell layer
- granular layer
- keratin layer
where are melanocytes loacted?
- in the basal layer
what are blaschko’s lines?
- development growth pattern of skin
- lines become apparent when some diseases of skin or mucosa maifest themselves into these patterns
what five layers does the skin consist of?
- epideris
- appendages (nails, hair, glands, mucosae)
- dermo-epidermal junction
- dermis
- sub-cutis
what is the sub-cutis?
predominantly fat
name three key cells in the epidermis
- melanocytes
- langerhans cells
- merkel cells
name three body sites where the epidermis may vary
- scalp
- armpit
- sole of foot
skin on palm
abdominal skin
scalp skin
what three factors control epidermal turnover?
- growth factors
- cell death
- hormones
how many days does it take for the epidermis to regenerate?
28 days
where do keratinocytes migrate from?
basement membrane
purpose of keratinocytes?
- preserve agains microbial, viral, fungal and parasitic invasion
- protect against UV radiation
- minimise heat, solute and water loss
what layer of the epidermis?
- usually one cell thick
- small cuboidal
- lots of intermediate filaments (keratin)
- highly metabolically active
basal layer
what epidermis layer?
- large polyhedral cells
- lots of desmosomes (connections)
- intermediate filaments connect to the desmosomes
prickle cell layer
what layer of the epidermis?
- 2-3 layers of flatter cells
- large keratohyalin granules
- contain filaggrin and involucrin
- lamellar bodies
- high lipid content
- cell nuceli and organelles lost
granular layer
what layer in the epidermis?
- overlapping non-nucleated cell remnants
- insoluble cornified envelope
- 80% keratin and filarggrin
- lamellar granules release lipid
- acts as a tight waterproof barrier
keratin layer
purpose of the teeth being keratinised?
to deal wtih friction/pressure
name some organs that are lined by mucosal membrane
- eyes
- mouth
- nose
- genito-urinary
- Gi tracts
is the lining of mucosa keratinised or non-keratinised?
non-keratinised
what two functions do desmosomes allow for in the prickle cell layer?
- adhesion
- flexibility
defin a scar in terms of the epidermal layers affected?
a scar is defined as the appendages (nails, hair, glands, mucosae) no longer being present
what is the pilosebaceous unit?
between hair and grease producing gland (the two are always together)
- important concept for acne
how does fillagrin play a role in water retention?
- fillagrin gets chopped (proteolyzed) by proteases
- the amino acid breakdown products contain a very important feature that RETAINS WATER
- they bind water molecules so they cant excape through the keratin layer
- very important in regulating skin hydration
what types of cells make up the majority of the epidermis?
keratinocytes
three other types of cells in the epidermis apart from kertinocytes?
- melanocytes
- langerhans
- merkel cells
what are these cells in the epidermis?
- migrate from neural crest to the epidermis in he first 3 months of foetal development
- located in the basal layer and above
- pigemnt that produces dendritic cells
melanocytes
what are melanosomes?
organelles in melanocytes
- transported to the tip and taken up be neighouring keratinocytes
- melanin forms thicj brown coloured cap that will not let light penetrate
- to naked eye would look like a mole or a brown hugh
what is the purpose of melanin forming a coloured cap in the basal cell layer?
to protect stem cells from UV radioation as light is not able to penetrate through
what drives the process of melanin granules forming the brown cap in the basal cell layer? (causing moles/ brown hughes)
Hormonally driven
- alpha melanocyte hormone
what can trigger the alpha melanocyte stimulating hormone to carry out the transportation of melanocytes to basal cell layer?
UV radiation activates the tyrosinase pathway
what do melanocytes do to tyrosine?
convert tyrosine to melanin pigment
what cells are responsible for the transport of melanin pigment?
melanosomes
disorder in which the alpha melanocyte stimulating hormone is produced in excess by the pituatry?
= more melanin
nelson’s syndrome
what type of cell is this in the epidermis?
- originates in the mesenchyme - bone marrow
- prickle cell level in the epidermis
- also found in dermis and lymph nodes
- they detect microbes and are involved in skin immune system
- pick up the antigen in skin and circulate it to lymph nodes via the lymphatic system
- birbeck granules are present (tennis rackets)
langerhans cells
what type of cells are these in the epidermis?
- basal layer
- between keratinocytes and nerve fibres
- mechanoreceptors (somatosensory receptors)
- close to the skins surface near the nerve endings
- can turn into a rare, dangerous type of tumour
merkel cells
what is another name for a hair follicle?
pilosubaceous unit
name two component structures that make up the hair follicle?
- epidermal component
- dermal papilla (finger like projection arranged into double row to increase surface area between dermis and epidermis)
what always comes next to a hair follicle?
subaeceous gland
how is hair pigmented?
via melanocytes above dermal papilla
what are the three phases of hair growth?
- anagen = gorwing
- categen = involuting (curl or curve)
- telogen = resting
what can influence hair growth?
hormonal influences
- e.g. thyroxine, androgens
what may be a reason for hair loss?
immune system
what happens during the telogen phase of hair growth?
hair remains in follicle until it is pushed out by growth of new anagen hair
what is the growth rate of nails?
0.1mm per day
name the root of the nail
the nail matrix
what is the lenula?
keratin structure that looks like a half moon
what is the cuticle for?
protecting the nail against bacteria etc.
What is the dermo-epidermal junction?
interface bewteen the epidermis and dermis
- underneath the basal cells
purpose of the demo-epidermal junction?
- support
- anchorage
- adhesion
- growth
- differentiation of basal cells
- semipermeable membrane that acts as barrier and filter
what cells are contained in the dermis?
- fibroblasts (mainly)
- macrophages
- mast cells
- lymphocytes
- langerhans
type of fibres in the dermis?
- collagen (90%)
- elastin
other components that make up the dermis?
- muscles
- blood vessels
- lymphatics
- nerves
describe the flow of blood in the skin
- arteriole
- precapillary sphincters
- arterial venous capillaries
- post-capillary venules
- collecting venules
what type of plexuses are in the skins blood vessels?
horizontal plexus
what is a plexus?
branching network of vessels or nerves
what do lymphatic vessels in the skin drain?
continual drainage of…
- plasma proteins
- extravasated cells
- excess interstitial fluid
role of lymphatic vessels in immune surveillance?
- circulates lymphocytes and langerhans cells
- channels micro-organisms/toxins
what are the nerve types in the epidermis + dermis?
somatic sensory
what nerve supply is present in the skin?
autonomic nerve supply
name the special receptors in the skin?
- Pacinian corpuscles
- Meissners corpuscles
receptors in the skin that can sense when theres pressure on it
pacinial corpuscles
nerve endings responsible for fine, discriminative touch and vibration sensations
Meissners corpuscles
what is the pilosubaceous unit?
- epidermal component plus dermal papilla
what are the names for the three types of skin glands?
- sebaceous
- apocrine
- eccrine
What gland is this?
- open into papillary canal
- widely distributed
- hormone sensitive: become more active produce more oil when puberty hits
- helps hair fight against infection from fungal and control moisture loss
- important for acne
sebaceous gland
what gland is this?
- real purpose isnt truly know
- develop as part of the pilo-sebaceous unit
- produce oily fluid
- may produce odour after bacterial decomposition
- cell lined
- androgen dependent
apocrine sweat gland
what gland is this?
- sweat gland
- triggered by ANS
- react when you are hot, nervous, stressed etc.
- help with thermoregulation, cool by evaporation
- dilate when body is hot
- present everywhere but especially in areas that get sweaty
- sympathetic cholinergic nerve supply
- help with filtration
eccrine glands
4 functions of the skin?
- barrier function
- metabolism + detoxification
- thermoregulation
- immune defence
- sensory function
what two metabolism pathways is the skin involved in?
- vitamin D metabolism
- thyroid hormone metabolism
Name the 4 factors in the skin that contribute to defense
- structure
- cell types
- cytokines, chemokines, eicosanoids, antimicrobial peptides
- genetics
what parts of the structure of skin contribute to immunological defence?
- keratin layer (stratum conreum)
- stratification
what are cytokines, chemokines, eicosanoids and antimicrobial peptides?
chemical signals that influence cell behaviour or help target pathogens
where are T cells produced?
bone marrow
where are T cells sensitised?
In the Thymus (in the neck)
what two things does antigen recognition and T cell activation involve?
interaction with…
- T cell receptor (TCR)
- Major histocompatibility complex (MHC)
what enhances Ag recognition and T cell activation interactions with TCR and MHC?
- CD4+ helper cells
- CD8+ cytotoxic T cells (CTL’s)
what do TH1 activate?
macrophages to destroy microorganisms
What do TH2 cells do?
help B cells to make antibiotics
interleukin associated with TH1?
IL2, IFNg
what interleukins are associated with TH2?
- IL-4
- IL-5
- IL-6
what are CD4+ cells?
helper T cells
what are CD8+ cells?
cytotoxic T cells (CTL’s)
purpose of CD8+ cytotoxic T cells?
- can directly kill infected cells
- important portection against viruses and cancer
what should healthy skin contain?
- t lymphocytes in both epidermis and dermis
what type of T cells are found on the epidermis mainly?
mainly CD8 T cells
- to kill microbes
what types of T cells are found in the dermis?
- CD4 AND CD8
name another subset of T cell (other than CD4/CD8) that are found in the skin
NK cells (natural killer cells)
what type of response are CD4 Th cells associated with?
inflammation
what pathologies are CD4 Th cells associated with?
- Psoriasis
- atopic dermatitis (eczema)
what pathology are TH1 cells related to?
psoriasis
what pthology are TH2 cells related to?
atopic dermatitis (atopic eczema)
what are dendritic cells?
- tree like branches
- initiate adaptive immune response
- most potent type of antigen presenting cells
- from bone marrow
what are the two types of dendritic cells found in the dermis?
- Dermal DC
- Plasmacytoid DC
what are dermal DC?
- cells more like helper dendritic cells
- involved in antigen presentation
- secrete cytokines and chemokines
what are plasmacytoid dendritic cells?
- more aggressive than dermal DCs
- produce interferon alpha (this notifies other cells to increase anti-viral defence)
name the 3 other immune cells in the dermis other than dendritic cells?
- macrophages
- neutrophils
- mast cells
function of macrophages?
- engulfs other cells to produce cell debris
function of neutrophils?
- circulating leukocytes
- attracted to tissue by chemokines
- make more chemkines and cytokines
- are also phagocytic
function of mast cells?
- found in barriers
- moderate IgE response
- binding of IgE causes mast cell activation and release of inflammatory markers
- phagocytotic cells
what happens when keratinocytes in the epidermis are under stress?
- release factors that stimulate plasmacytoid dendritic cells to produce IFNalpha
- release IL-1/IL-6 and TNF
what is the fundamental pathological process in psoriasis?
chronic inflammation
what may cause psoriasis?
- environmental factors with genetic susceptibitilty
what TWO histological features must a patient have to have atopic eczema?
- BARRIER BREAK in the skin (fillargin)
- Overreactive immune response
what are interleukins and interferons?
signalling molecules realeased by Th cells for an immune response
when is an immune response launched?
- name the important group of proteins involved in this process
when the cells cant recongise eachother through connecting via cell surface receptors
may be due to…
- cancer cell
- microbe
- antigen
- MHC protein is involved
where do major histocompatibility complex proteins come from?
chromosome 6
Describe type 1 MHC molecules
- found on almost all cells
- presents antigen to cytoxoic T cell
- present human antigens to stop them from being killed
describe type 2 MHC cells
- found on antigen presenting cells i.e. B cells, dendritic cells and macrophages
- present antigens to T helper cells
- cell type presents exogenous cell material
what is porphyria?
- group of disorders that affect the production of heme
- when heme synthesis is halted it causes the build up of one of its precursor molecules
what are porphyrins essential for?
function of haemoglobin
- protein in the red blood cell that links to porphyrin binds iron and carries oxygen to your organs and tissues
what is fitzpatrick sun reactive skin phototypes
characteristic present at birth
- people with photsensitivity may burn easily on exposure to sun
Main types of grouped porphyrias?
- erythropoietic protophyria (photoxic skin porphyrias)
- blistering and fragile skin porphyrias
- acute attack porphyrias (some have no skin involvement)
- severe congenital porphyria (e.g. congenital erythopoietic porphyria)
- porphyria cutanea tarda
in what ways can the disease present itself?
- acute neurovisceral
- non-acute cutaneous
- mixed
where do the built up haem precursors end up?
- faeces
- urine
- non-acute cutaneous
- erythrocytes
why do the heme precursors build up?
one of the enzymes in the heme pathway is deficient
what causes blisters and skin fragility in porphyria?
- caused by an accumulation of water soluble porphyria on skin surface that have been oxidised by free radicals or sunlight
what are virulence factors?
- enables a foreign microbe to be able o achieve colonisation of a host and enhance its potential to cause a disease
- disease caused by specific component of pathogen e.g. toxin
- toxic shock
- strains, sub species, carrying different genes that influence pathology
- can be interchanged with virulence
which area of the body does staphylococcus tend to colonise?
- sebaceous gland
- e.g. front of the nose
how can s.aureus infection progress so vastly?
- e.g. go from superficial lesions to systemic to toxinoses
it has a wide number of different virulence factors they express, different proteins
name the two main broad species of staphylococci that cause skin conditions?
- staph epidermis
- staph aureus
what is a coagulase test?
whether something coagulases plasma
name some virulence factors from staph. aureus
- fibrinogen binding protein - adhesin
- coagulase - clots plasma
- leukocidin - inactivates leukocytes
- TSST-1 (toxin) - shock, rash, desquamation
what is an endotoxin?
toxin present inside a bacterial cell that is released when it disintegrates
does staph. aureus test coagulase positive or negative?
coagulase positive
what bacteria strain result is this?
- common human pathogen
- produces enzymes
- flucloxacillin is primary treatment
- grows best in aerobicly but can also grow anaerobically
staphyloccus aureus
name the three strains of staph aureus that produce toxins
- enterotoxin
- staphylococca scalded skin syndrome toxin (SSST)
- panton valentine leucocidin (PVL)
strain of bacteria causes…
- boils/carbuncles
- cellulitis
- infected psoriasis
- impetigo
- woud infections
- SSST
- PVL
- 30% of hospital staff carry it
staph. aureus
what makes staph aureus highly effective as a pathogen?
multiple virulence factors
what is MRSA?
- bacteria thats resistent to several widely used antibiotics
- spread in the community
- can be infected by things that have touched infected skin
MRSA treatment options?
- doxy
- co-trimoxazole
- clindamycin
- vancomycin
does staph. epidermidis test positive or negative for the coagulase test?
coagulase negative
where does coagulase usually hang around in the bod for staohylococcus epidermidis?
- skin
- mucous membrane
- often associated with prosthetics in the body, heart valves, knee replacements etc.
when would infection usually occur for staphylococcus epidermidis?
- usually in the immunocomprimised in hospital
- associated with foreign objects e.g. catheters
name 3 competitive skin commensals
- staph. E
- corynebacterium Sp.
- Propionbacterium Sp.
what is this?
- positive coagulase cocci
- causes UTI in women of child bearing age
- novobiocin resistent (all other staph are sensitive)
staph saprophyticus
what is this?
- cocci in chains alpha haemolytic
- pathogen most common cause of pneumonia
strep pneumoniae
what is this?
- cocci in chains alpha haemolytic
- commensla bacteria of mouth, throat and vagina
- can cause infective endocarditis
strep viridans
- gut commensals that are not haemolytic
- inhabits Gi tract
- gram positive
enterococcus species
- gram positive cocci in chains
- classified by beta haemolysis
- infected eczema
- impetigo
- cellulitis
- erysipela
- necrotising fascitis
streptococcus pyogenes
how is streptococcus pyogenes treated?
penicillin
(also flucloxacillin)
how to test a boil of a furuncle?
- swab if lesion is broken
- if its a depper lesion take a tissue or pus sample
- blood culture if appropriate
- rare condition
- caused by an out of proportion massive immune system release of cytokines etc.
- antigen binds appropriatle and activates 1 in 5 T cells (incredibly high)
toxic shock syndrome
symptoms and warning signs of toxic shock syndrome?
- fever (over 39 degrees)
- diffuse macular rash and desquamation
- hypotension (less than 90 systolic)
- greater than 3 organ systems involved
- bacterial infection along fascial planes below skin surface
- rapid tissue destruction
- life threatening soft tissue disease
- characterised by rapidly progressive necrosis that spreads in subcutaneous tissue into deep fascia
- 25% mortality rate
necrotising fascitis
what is necrotising fascitis secondary to?
- organ failure and
- streptococcal toxic shock syndrome
Name 7 basic tissue groups found in the skin
- epithelium
- glands
- muscle
- hair
- adipose (fatty) tissue
- connetive tissue
- nervous tissue
- nails
where may there be more undulations in the epidermis?
ridges and grooves of fingerprints for example
what are these glands stained in purple?
sebaceous glands
- produce sebum (oily film on nose and forehead skin)
what are these glands?
sebaceous glands
what glands are found over whole bodyd except lips and genitals
- regulate heat and salt loss
eccrine glands
what glands?
- limited to axillae/nipple/genitals
- develop at puberty and open into hair follicles
apocrine glands
smooth muscle fibres attached to hair follicles that help with hair standing on end?
- also present in walls of blood vessels
arrector pili
what are free nerve endings for?
to sense pain
located in basal layer of epidermis
what is located at the base of the hair follicle?
Hair bulb contains…
- hair matrix
- dermal papilla
where is soft and hard keratin located in the hair?
- SOFT: central medulla
- HARD: outer cortex and cuticle
where is the nail matrix located?
base of nail
purpose of the hyponychium?
secures the free nail edge
implications of skin failure?
- loss of thermoregulation (may contribute to cardiovascular instability)
- increased risk of infection
- failure of homeostatic function (fluid and electrolyte losses)
what is fibroplasia?
fibroblasts lay down matrix and contract the wound
what is angiogenesis?
endothelial cells develop into new blood vessels
what layer of th skin do first degree burns reach?
epidermis only
what layer of skin do second degree burns reach?
epidermis and dermis
what layer of skin do third degree/ full thickness burns reach?
extends beyond dermis
what is surface slough?
mixture of dead cells, polymorphs and bacteria
- yellow/green in colour
- may be quite adherent to underlying tissue
- has inhibitory affects on the healing ability of the wound
- should be removed chemically or with physical debridement (larval therapy can also be used)
three stages of wound healing?
- inflammation
- proliferation
- tissue remodelling
why is primary intention wound healing more rapid than secondary?
wound edges are opposed so less of a defect to heal
