Week 1 Flashcards
The layers of skin
Epidermis
Glands / hairs/ nails
Dermis
Sub cutis
What is the layer between epidermis and dermis called
Dermo-epidermal junction
Function of dermo-epidermal junction
Semi permeable membrane filtering substances that crosses
Anchors the epidermis to the dermis
The dermis is mainly
Connective tissue
The Sub cutis layer is mainly
Fat
The layers of epidermis (from top to low)
Keratin layer
Granular layer
Prickle cell layer
Basal layer
What are basal stem cells
Cells that can differentiate into a specific type of cell of the epidermis and migrate through it to replace it
Where are basal stem cells located at
Basal layer of epidermis
What cells are in the epidermis
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Basal cells
Which type of cells make up the most of epidermis
Keratinocytes
Function of langerhans cells
Dendritic cells involved in immunological functions of the skin
Function of Merkel cells
Mechanoreceptor cells
Function of melanocytes
Pigment producing dendritic cells protecting against sun damage
Where are langerhan cells located at
Prickle cell layer of epidermis
Where are Merkel cells located at
Basal layer of epidermis
Where are melanocytes located at
Basal layer of epidermis
Basal cells at the basal layer are which type of cells
Cuboidal cells
Features of structure of prickle cell layer
Large polyhedral cells
with a lot of desmosomes in between the cells acting as connections
Features of granular layer
2-3 layers of flatter cells
Cells do not have nuclei
Lamellar bodies
Features of keratin layer
Mostly corneocytes (dead keratinocytes)
Lamellar granules
Waterproof barrier
Function of keratin layer
Prevents entry of unwanted substaces
Prevents excessive loss of water
The cells at the outermost layer of epidermis are
Dead cells (corneocytes) which are continually shed and replaced from below
What makes the keratin layer waterproof
Cells are close to each other
Lamellar granules release lipids which is hydrophobic
How do melanocytes protect us against sun damage
- Melanocytes produce melanin
- Melanin absorb light and are contained in melanosomes
- Melanosomes are then transported to adjacent keratinocytes by dendrites of the melanocytes
- This induces pigmentation and protect the basal cells against UV radiation by absorbing the UV light (because it is black)
What causes different skin colours
- Due to different activity level of melanocytes.
- e.g. melanocytes in black skin has higher activity level = produce more melanin = more pigmentation - Ratio between eumelanin and phenomelanin
What is vitiligo and what causes it
Vitiligo = patches of skin losing colour
Due to autoimmune destruction attacking melanocytes
What causes albinism
Genetic disorder reducing melanin production
What causes skin hyperpigmentation in Addison’s disease
High ACTH stimulating melanocytes to produce more melanin
Structure of hair follicles
Specialized keratins
Hair papilla is in the dermis layer and it extends into the epidermal layer and out of the skin
Sebaceous gland next to it
Arrector pili muscle attached to the hair follicles
Function of arrestor pili muscle
It contracts to erect the hair when you’re cold to provide thermal insulation
= causes goosebumps
What condition affects the arrestor pili muscle
Leprosy
What causes hair to be pigmented
Melanocytes in epidermis
What are the phases of growth of hair
Anagen
Catagen
Telogen
What is anagen
Growth of new hair
What is catagen
end of active hair growth and cuts individual hairs off from the blood supply and from the cells that produce new hair (forms club hair)
What is telogen
resting period when strands remain in their follicles till they shed
Most hair at any time are in which phase
Anagen
Why can animals’ fur shed at the same time whereas human hair does not
Because animals have synchronous telogen phase whereas in humans the telogen phase of each hair is different
List the outer structures of the nail
Nail plate
Nail folds
Eponychium
What are the nail folds
The skin around the nail that protects the margin of the nails
What is the eponychium
keratin layer of the skin that extends over the proximal nail plate
What are the structures underneath the nail plate
Nail bed
Germinal matrix
Hyponychium
What is the nail bed
Directly underneath the nail plate providing a smooth surface for the nail plate to glide over during growth
How do nail plates grow
Cells in germinal matrix divide and become keratinised. The continuous cell division pushes the nail plate, letting it glide over the nail bed = nail becomes longer
What is the hyponychium
The area underneath the free edge of nail plate
What are the 2 layers of dermis
Papillary dermis
Reticular dermis
Describe the papillary dermis and reticular dermis layers
Papillary dermis is thinner and it is just below the epidermis
Reticular dermis layer is thicker and contains several structures
What structures are in reticular dermis layer
Blood vessels
Pilosebaceous units (sebaceous gland + hair follicle)
Lymphatics
Nerves
Structures in dermis
Blood vessels
Lymphatics
Nerves
Collagen and elastin fibres
Hair follicles
Glands
Cells
What cells are present in dermis
Macrophage
Mast cells
Langerhans cells
Fibroblasts
What are the 2 types of aging
Intrinsic and extrinsic
What is intrinsic aging
Inevitable physiological process that causes skin to look more saggy and less firm, hollowed cheeks as you age
What is extrinsic aging
Skin aging due to external factors such as UV light, smoke particles, pollutants on top of intrinsic aging
If an area of skin aging is mostly due to extrinsic aging, what would the features be
Coarse wrinkles (deep wrinkles)
Loss of elasticity
Rough texture appearance
Hypertrophic photoaging
If an area of skin aging is mostly due to intrinsic aging, what would the features be
Fine wrinkles
Dry skin
Thin skin
Telangiectasia
Atrophic photoaging
Atrophic photoaging increases the risk of
Non melanoma skin cancer
What type of plexus do vessels in dermis form
horizontal plexuses
Dilation of lymphatic vessels in the dermis can cause
Chronic lymphoedema
Dilation of blood vessels in the dermis can cause
Angioma
What structures are responsible for the innervation of the skin
Free sensory nerve endings
Special receptors
Motor nerve fibre
What are the special receptors for sensory innervation of the skin
Pacinian corpuscle
Meissners corpuscle
Pacinian corpuscle is for what type of sensory
Pressure
Meissner corpuscle is for what type of sensory
Vibration
Where is Meissener’s corpuscle located at
Papillary layer of the dermis
Where is Pacinian corpuscle located at
Reticular layer of dermis
What is alopecia areata and what causes it
Patchy hair loss
Due to autoimmune destruction of hair papilla causing hair to fall out
Does hair grow back in affected areas in alopecia
Yes, because the stem cells are not attacked
What are the 3 types of glands present in skin
Apocrine
Eccrine
Sebaceous
What is eccrine gland
Sweat glands that open directly onto the skin surface
What is apocrine gland
glands that drain into hair follicles
What are sebaceous glands
Glands in hair follicles that secrete sebum
When do sebaceous glands become active and start producing sebum
During puberty
What happens when sebaceous glands are clogged because they produce too much sebum
Acne
Function of sebum
Control moisture loss from skin
Protects against infection
On which body parts are sebaceous glands found
Everywhere except Soles and palms
On which body parts are eccrine glands found
Everywhere ESPECIALLY palms, soles, forehead and axillae
Function of eccrine gland
Thermal regulation
Aid grip
On which body partsare apocrine glands found
Axillae
Groin
Eyelids
Ears
Perineal region
Functions of the skin
Barrier
Metabolism and Detoxification
Thermoregulation
Immune defense
Sensation
What is metabolised by the skin
Thyroid hormones
Vitamin D
What does the skin do to thyroid hormones
Converts T4 into metabolically active T3
Around how much % of thyroid hormones are metabolised (converted) by the skin
80%
Role of Vitamin D
To increase serum Ca2+ when there is a decrease.
By increasing absorption of Ca2+ from digested food in intestines and reabsorption of Ca2+ in kidneys
2 forms of Vitamin D
Vitamin D2
Vitamin D3
Which form of Vitamin D is more effective in raising serum vitamin D (metabolically active form)
Vitamin D3
Vitamin D2 is obtained by
Ingestion of plants esp mushroom
Vitamin D3 is obtained by
Mostly made by the skin
ingestion
How does the skin synthesise vitamin D3
By the action of ultraviolet B from sunlight on 7-dehydrocholesterol
What happens to vitamin D3 after it is synthesised in the skin
Stored in the liver then it is converted into its biologically active form in the kidneys
Causes of vitamin D deficiency
Lack of sunlight
Lack of vitamin D in diet
Malabsorption
Kidney disorders
Vitamin D deficiency can cause
Osteomalacia
Rickets in children
Secondary hyperparathyroidism
What is rickets
A condition that affects the development of bones in children causing bone pain, poor growth and weak bones that can lead to bone deformities
What can be caused if there is damage to skin barrier
Fluid loss
Protein loss -> hypoalbuminaemia
Infection
What factors that contribute to skin act as an immunological defence against pathogens
Keratin layer
Keratinocytes
Immune cells of the epidermis and dermis
How do keratinocytes provide immunological defence against pathogens
When they sense pathogens using cell surface receptors:
Produce anti-microbial peptides (AMP)
Produce cytokines and chemokine
What are the immune cells in the epidermis
Langerhan cells
T cells
What are the immune cells in the dermis
T cells
Dermal dendritic cell
Plasmacytoid dendritic cell
Macrophages
Neutrophils
Mast cells
What is a characteristic feature of Langerhan cells
Birbeck granules
Which type of T cell is the main T cell found in dermis layer
CD8+
Which types of T cells are found in the epidermis layer
CD4+ and CD8+
What are CD8+ cells
Differentiate into cytotoxic cells
What are CD4+ cells
Helper cells that differentiate into different helper cells to produce different cytokines
They also instruct CD8+ cells and B cells
What are the different Helper T cells differentiated from CD4+
Th1
Th2
Th17
Th1 function
Secrete IL2 and IFNy to activate macrophages
Th2 function
Secrete IL4 IL5 IL13 to stimulate B cells
Th17 function
Secrete IL17 to modulate immunity
Function of the dendritic cells in the dermis
To present antigens to T and B cells
Which immune cell is responsible for allergy
Mast cells
What type of disorder is psoriasis classified as
Autoimmune disorder
Pathogenesis of psoriasis
- Keratinocytes under stress release AMP and cytokines that stimulate plasmacytoid dendritic cells in dermis to produce other cytokines
- these chemical signals causes dendritic cells to present to T cells
- Th1 and Th17 predominant
- Causing inflammation cascade
- Causes keratinocyte proliferation and increased epidermal turnover
What are the 5 types of psoriasis
Chronic plaque psoriasis
Inverse psoriasis
Guttate psoriasis
Pustular psoriasis
Generalised psoriasis
Which immune complex is mainly present in psoriasis
Th1
Th17
Which type of psoriasis is the most common
Chronic plaque psoriasis
What are the clinical features presented in chronic plaque psoriasis
Plaques that are :
Symmetrical
Scaly
Well demarcated
itchy
Where are chronic plaque psoriasis usually found
Extensor surface distribution
Scalp
Lower back
Where are the extensor surfaces
Front of the knee
Back of the elbow
What are the clinical features caused by inverse psoriasis
Smooth erythematous plaques
Where is inverse psoriasis usually found
Areas where the skin rubs against each other
- axilla
- groin
- gluteal cleft
- genital area
What clinical features are caused by guttate psoriasis
Sudden emergence of multiple small tear drop shaped erythematous plaques
Guttate psoriasis usually occurs after
Streptococcal infection e.g. Strep throat
What may be a common illness patients with Guttate psoriasis have a week before rashes appear
Tonsilitis
What clinical features are presented in pustular psoriasis
Multiple red round spots (petechiae)
Multiple pustules
Where are pustular psoriasis commonly found and what is the other name for pustular psoriasis
On palms and soles
Hence it is also called palmoplantar pustulosis
What are the subtypes of generalised psoriasis
Erythrodermic psoriasis
Generalised pustular psoriasis
Risk factors for developing psoriasis
Genetics
Obesity
Smoking
HIV
Risk factors that can exacerbate psoriasis
Skin trauma (Koebner Phenomenon)
Streptococcal infection
Stress
Drugs
Withdrawal of steroids
Hormones
What is Koebner’s phenomenon
Skin trauma leads to new lesions occurring at sites of skin trauma meaning it triggers psoriasis in an area that was not previously affected
Koebner’s phenomenon can be seen in which other conditions except from psoriasis
Vitiligo
Lichen Planus
What drugs can exacerbate psoriasis (BALI)
Beta blockers
ACEi
Antimalarials (hydroxychloroquine)
Lithium
Indomethacin (NSAID)
Psoriasis is associated with which other conditions
Psoriatic arthritis
IBD
higher risk of developing other autoimmune diseases
Apart from the skin, what other signs of psoriasis can be see
Nail involvement
- nail pitting
- nail onycholysis
- thickening of nail bed
Why should patients with psoriasis avoid scratching
Because it can lead to skin trauma -> Koebner’s phenomenon -> psoriasis flare up
What is a sign of psoriasis
Auspitz sign
What is Auspitz sing
Removal of surface scale reveals tiny bleeding points
What will a biopsy of psoriatic skin show
Thickened epidermis
Parakeratosis: Retention of nuclei of corneocytes at keratin layer (they should not have nuclei because they are dead cells)
Inflammatory cells
What is parakeratosis
Retention of nuclei of corneocytes at keratin layer due to abnormal differentiation and proliferation of keratinocytes
Management of chronic plaque psoriasis
- Topical therapy
- Phototherapy
- Systemic therapy
Describe the topical therapy for psoriasis
Emollients with
1. Topical steroid + Topical vitamin D
2. Stop topical steroid but continue topical vitamin D twice daily
3. Stop topical vitamin D but continue topical steroid twice daily
Examples of topical vitamin D
Calcipotriol
Calcitriol
Why do you need to stop using topical steroid after certain amount of time
To avoid side effects such as unstable psoriasis / striae
How long can you use a potent topical steroid for
4 weeks
Mildly potent topical steroids are used in psoriasis for areas such as
Face
Groin
Breasts
What are the drugs commonly used for topical steroid + topical via D therapy for psoriasis
Betamethasone (steroid) + calcipotriol
What are the alternatives topical treatments for psoriasis if topical steroids + vitamin D are ineffective / contraindicated
Tar
Dithranol
When is phototherapy indicated for psoriasis
If
- extensive psoriasis
- nail disease which cannot be treated topically
- ineffective topical therapy
What types of phototherapies are there for psoriasis
UVB
PUVA (psoralen + UVA)
When is PUVA used and why shouldn’t it be used unless necessary
PUVA used if UVB is ineffective
PUVA is not used unless necessary due to its side effects: increase risk in skin cancer, skin irritation
PUVA + usage of which drug can increase risk of skin cancer
Ciclosporin (medication used in systemic therapy for psoriasis)
PUVA should be avoided in which group of people
- those that are using / likely to use ciclosporin
- young
- light skin type (they are already prone to skin cancer)
When is systemic therapy indicated in psoriasis
If psoriasis is not controlled by topical therapy
+ significant impact on wellbeing
+ extensive psoriasis / nail disease / ineffective phototherapy
Describe the order of drugs used in systemic therapy for psoriasis
- Methotrexate
- Ciclosporin
- Acitretin
Contraindications for methotrexate
Those that are pregnant / planning to be pregnant
Advise given to patients who are going to use methotrexate
Contraception during treatment and 6 months after ending treatment
When is ciclosporin used in psoriasis
For patients considering pregnancy
For rapid disease control
For patients with palmoplantar pustulosis
What does atopy mean
When a patient has predisposition to abnormally exaggerated IgE response to allergen
Atopic individuals are at risk of developing which conditions
Atopic dermatitis
Asthma
Allergic rhinitis
Food allergy
Atopic dermatitis is most common in
Children, most present symptoms by the age of 5
Causes of atopic dermatitis
Multifactorial - genetics, environment, immunological
What genetic factor contributes to causing atopic dermatitis
Mutation in FLG gene which codes for filaggrin protein. Filaggrin protein is required for effective skin barrier hence mutation in FLG gene -> ineffective skin barrier
How does ineffective skin barrier contribute to atopic dermatitis
Ineffective skin barrier allows antigens to enter the skin more easily which causes sensitization of the allergen then trigger inflammation in allergen stage
Which immune complexes are mainly present in atopic dermatitis
Th2
Mast cells
Patients with atopic dermatitis are more likely to have
Food allergy
Allergic rhinitis
Asthma
What can trigger flares of atopic dermatitis
Certain chemicals in soaps / detergents / shampoo / perfume
Stress
Food
Fabrics
Hormones
Dry weather
Symptoms of atopic dermatitis
Pruritus
Erythema
Scaling
Dry skin
Nodular pruigo
Flexural distribution of symptoms in older children / adults
What is the distribution of atopic dermatitis in infants
Extensor surfaces
Face - cheeks
Neck
Scalp
Eyelids
What are nodular pruigo
Very itchy nodules most commonly present in black people with atopic dermatitis
What can you see in skin biopsy of atopic eczema
Spongiosis - intraepidermal oedema
Diagnostic criteria for atopic dermatitis
Pruritus + 3 or more of the following:
- flexural dermatitis (or extensor dermatitis in infants)
- PMH of flexural dermatitis
- PMH of asthma / allergic rhinitis
- Dry skin in the last 12 months
What is the first line treatment for atopic dermatitis
Identify and avoid triggers
Management for mild atopic dermatitis
Emollients
Mild potency topical steroids (hydrocortisone)
Management for moderate atopic dermatitis
Emollients
Moderate potency topical steroids
Topical calcineurin
Bandages
Management for severe atopic dermatitis
Emollients
Potent topical steroids
Topical Calcineurin
Phototherapy
Systemic therapy
What drugs are used in the systemic therapy for atopic dermatitis
Methotrexate
Azathioprine
Prednisolone
Which drugs that are used in systemic therapy for atopic dermatitis are not safe in pregnancy
Methotrexate
Azathioprine
Complications of atopic dermatitis
Infection due to ineffective skin barrier
Mental health
What infections are at increased risk due to atopic dermatitis
S aureus
Eczema herpeticum
What symptoms does S aureus infection cause in a patient with eczema
Oozing rash (weeping eczema) fluid seeping onto skin surface due to blood vessel dilatation causing fluid to leak out
Oedema
Eczema herpeticum is caused by
Herpes simplex virus
Treatment of eczema herpeticum
IV aciclovir
What does acanthosis mean
Increased thickness of epithelium
What does parakeratosis mean and in which condition is it present
Persistence of nuclei in the keratin layer
Present in psoriasis
What does hyperkeratosis mean
Increased thickness of keratin layer
