Introduction to Dermatology Flashcards
What are the 3 layers of the skin?
- Epidermis
- Dermis
- Subcutis
What are the 4 layers of the epidermis?
- stratum corneum
- stratum granulosum (granular cell layer)
- stratum spinosum (spiny layer)
- stratum basale (basal cell layer)
What cell makes up most of the epidermis?
It is the uppermost layer of the skin and is mostly keratinocytes
What is found in the stratum basale?
What is its purpose?
- source of epidermal stem cells
- site of cell division
- contains melanocytes (which produce the pigment melanin)
What is found in the stratum spinosum and what is its function?
- central layer of epidermis
- contains desmosomal junctions that link keratinocytes together
What is found in the stratum granulosum?
What is its function?
- cells contain keratohyaline granules
- keratinocytes produce and secrete lipid to prevent water loss from the skin
- filaggrin protein retains water within keratinocytes
What is found in the stratum corneum and what is its function?
- desquamating keratinocytes forming a flattened keratinised cell layer
- acts as a barrier
How long does the process of cell migration from the stratum basale to stratum corneum take?
around 30 days
Which parts of the body contain an additional fifth layer of epidermis?
areas of thick skin such as the palms of the hands and soles of the feet
this 5th layer is the stratum lucidum
What is found in the stratum lucidum and where is it?
it is between the stratum granulosum and stratum corneum
it is paler and contains compact keratin
What are the 2 different components of the dermis?
- Papillary dermis
- Reticular dermis
How thick is the dermis?
What comprises most of this layer?
- 1 - 4mm thick
- mostly made up of collagen
- strong but flexible
What is found within the dermis?
- fibroblasts
- blood vessels
- lymphatics
- immune cells (mast cells)
- nerves
- skin appendages (sweat glands, sebaceous glands, hair follicles)
What is the role of fibroblasts within the dermis?
production of collagen, elastin & glycosaminoglycans
What is the role of the dermal papillae within the dermis?
They increase the strength of the connection between the epidermis and dermis
The greater the folding, the stronger the connections made
What are the main components of the papillary layer of the dermis?
- fibroblasts
- small numbers of adipocytes (fat cells)
- phagocytes to fight infections that have breached the skin
- lymphatic capillaries
- nerve fibres
- Meissner corpuscles (touch receptors)
Why does the reticular layer of the dermis have a net-like appearance?
This is due to the tight meshwork of fibres
It contains both elastin and collagen
What are the main properties of the reticular layer of the skin?
- well vascularised
- rich sensory & sympathetic nerve supply
What are the roles of collagen and elastin in the dermis?
Elastin:
- elastin fibres provide elasticity to the skin, enabling movement
- found in reticular layer
Collagen:
- provide structure and tensile strength
- binds water to keep the skin hydrated
- found in both the papillary and reticular layers
What are the roles of the subcutis (hypodermis)?
- separates dermis from deep underlying structures (fascia, muscle)
- fat layer that provides insulation, energy, protection
- improves skin mobility
What are the 4 main skin appendages?
- hair
- nails
- sebaceous glands
- sweat glands
What is the role of sebaceous glands?
When do they become active?
Produce and secrete sebum for lubrication and waterproofing of the skin
Become active during puberty
What are the 2 different types of sweat glands and the main difference between them?
Eccrine gland:
- widespread across the whole body
- open directly onto the skin surface
Apocrine gland:
- found in the axillae & anogenital regions
- open into hair follicles
- become active during puberty
What is a pilosebaceous unit?
A unit containing:
- hair shaft
- hair follicle
- sebaceous gland
- arrector pili muscle
What are these layers?
What are the 6 main functions of the skin?
- thermoregulation (insulating hairs/fat, vasoconstriction/vasodilation, sweating)
- fluid balance (regulation of water loss)
- protection
- sensation (sensory neurones)
- Vitamin D synthesis
- aesthetics (cosmetic appearance)
In what ways does the skin provide protection?
Physical Barrier:
- mechanical, chemical & microbial stimuli
Immunological barrier:
- to pathogens
Protection against UV light:
- melanin production is involved in this
What can skin failure lead to?
- hyper- or hypothermia
- fluid loss
- dehydration
- malabsorption
- infection
- skin cancer
- death
What are the four phases of wound healing?
- haemostasis
- inflammation
- proliferation-migration
- remodelling
What is the main aim of the haemostasis phase of wound healing?
it begins at the onset of injury and aims to stop bleeding through coagulation
What happens during the haemostasis phase of wound healing?
- vasoconstriction occurs to restrict blood flow
- platelet activation & aggregation occurs after they come into contact with collagen, which seals the break in the blood vessel wall
- thrombin initiates formation of a fibrin mesh to trap platelets & form a clot
- coagulation
What is the main aim of the inflammatory phase of wound healing?
This focuses on destroying bacteria and removing debris to prepare the wound bed for the growth of new tissue
What are the 2 main processes that occur during the inflammation phase of wound healing?
vasodilatation & phagocytosis
What are the 2 main phagocytes involved in the inflammation phase of wound healing?
What are their roles?
Neutrophils:
- destroy bacteria & remove debris
- reach peak population 24hrs after injury & reduce greatly in numbers after 3 days
Macrophages:
- enter after neutrophils & continue to clear debris
- release growth factors
- release proteins that attract immune cells to the wound to facilitate tissue repair
How long does the inflammatory phase of wound repair usually last and what is it associated with?
lasts four to six days
associated with erythema, heat and pain
What are the 3 main things that occur during the proliferation-migration phase of wound repair?
- granulation tissue formation
- angiogenesis
- re-epithelialisation
What happens during the proliferation-migration phase of wound repair?
- granulation tissue fills the wound bed with connective tissue
- new blood vessels form
- wound margins contract and pull toward the centre of the wound
- epithelial cells arise from wound margins and migrate across the wound bed until the wound is covered with epithelium
What happens during the maturation phase of wound healing?
- new tissue slowly gains strength & flexibility
- collagen fibres reorganise and tissue remodels & matures
- scarring
What is a lesion?
lesion refers to an area of altered skin
What is meant by a rash?
a rash is an eruption on the skin
What is the difference between a macule and a patch?
- A macule is a small flat lesion
- A patch is a larger flat lesion
What is a papule?
a papule is a small, (<0.5cm diameter) solid, raised lesion
What is a plaque?
A plaque is a larger (>0.5 cm diameter), scaly, raised lesion
What is a nodule?
a nodule is a larger (>0.5cm diameter), solid, raised lesion with a deeper component
What is a vesicle?
a small (<0.5cm diameter), raised, clear fluid-filled lesion
What is a bulla?
larger (>0.5cm diameter), raised, clear fluid-filled lesion
What is a pustule?
small (<0.5cm diameter) pus-filled lesion
What is the difference between an erosion and an ulcer?
Erosion:
- superficial
- loss of some or all of the epidermis
Ulcer:
- deep
- complete loss of the epidermis and some of the dermis
What is the difference between a scale and a crust?
Scale:
- flakes of desquamated stratum corneum
- silvery appearance
Crust:
- dried exudate
What is meant by excoriation?
epidermal loss due to trauma
What is meant by lichenification?
thickening of the skin
What is meant by scarring?
fibrosis
What are the 5 different types of dermatological tests?
- simple excision
- skin scrapes / nail clippings / hair extraction
- skin swabs
- patch testing
- Doppler studies
When are skin scrapes / nail clippings / hair extraction performed?
performed when fungal infection or scabies is suspected
When is patch testing performed?
performed when contact allergic dermatitis is suspected
potential allergens are applied to the patient’s skin and they are observed over subsequent days for a reaction
When are Doppler studies performed?
a Doppler can measure ankle brachial pressure index (ABPI) which can identify peripheral artery insufficiency
this is often measured in patients with leg ulcers
What are the 3 methods used to take skin biopsies?
- curettage
- punch biopsy
- ellipse biopsy
What is involved in curettage?
a curette is used to remove a superficial skin lesion
What is involved in a punch biopsy?
punch, forceps and scissors are used to obtain a full thickness skin sample (often 3-4mm)
the resulting wound is either left alone or sutured
What is involved in an ellipse biopsy?
scalpel is used to remove larger and deeper areas of skin
resulting wound may require sutures, a skin flap or skin graft
