2a. Dermatological Principles Flashcards
What are the appendages of the skin?
Nails, Hair, Glands, Mucosae
What type of cell is the epidermis composed of?
Stratified squamous epithelium (mainly Keratinocytes)
What as the layers of the epidermis?
Basal Layer
Prickle Cell Layer
Granular Layer
Keratin Layer
What muscles allows hair to stand up?`
Arrector Pili Muscle
Describe the basal layer
Stem Cell layer One cell thick Small cuboidal cells Lots of intermediate filaments High metabolic activity
Describe the prickle cell layer
Large polyhedral cells
Lots of desmosomes with intermediate filaments
Describe the granular layer
2-3 layers of flatter cells
Large Keratohyalin granules
What do the granules in the granular layer contain?
Filaggrin
Describe the keratin layer?
Corneocytes - non-nucleated cell remnants
INSOLUBLE
What are lamellar granules?
Secretory organelles found in type ii alveolar cell sin the lungs and keratinocytes in the skin
What are the other cells in the epidermis?
Melanocytes, Lagerhans Cells, Merkel Cells
What are melanocytes?
Pigment producing dendritic cells.
Why do melanocytes have synaptic function?
They have synaptic function to release the melanin pigment.
How do melanocytes function?
Convert tyrosine to melanin pigment. Melanin absorbs lights
Why is melanin mostly at the top of the cell?
To protect DNA in the nucleus from damage
Where are langerhans cells found?
Prickle cell level in epidermis; dermis; lymph nodes
What is the function of langerhans cells?
Antigen presenting cells
What are racket organelles?
Possibly do something to do with antigen processing
Where are merkel cells found?
Basal layer - between keratinocytes and nerve fibres
What is the function of merkel cells?
Mechanoreceptors. They connect to the nerve endings and a direct connection to the CNS
What are the phases if hair growth?
Anagen - Growing
Catagen - Involuting
Telogen - Resting
What is the name of the layer of subcutaneous tissue beneath the dermis?
Hypodermis (superficial fascia)
Where do the arteries that supply the skin come from?
The dermis and the subcutaneous tissue
What is the pilosebaceous unit?
The hair follicle and all the appendages surrounding it
What is the pilosebaceous unit composed of?
Hair follicle Arrector pili muscle Sebaceous gland Hair root Apocrine sweat gland
What is the function of the sebaceous gland?
Produces sebum to lubricate the hair and connects the hair follicle
Where are the apocrine sweat glands found?
Axilla and genetalia
Where are the eccrine sweat glands found?
Skin of the forearms and legs
What is the dermo-epidermal junction?
Interface between epidermis and dermis
What is the role of the dermo-epidermal junction?
Support Anchorage Adhesion Growth Differentiation of basal cells
What is the dermis embryologically derived from?
Mesoderm
What is the function of the dermis?
A connective tissue support system for the skin
What cells are contained in the dermis?
Mainly fibroblasts Macrophages Mast cells Lymphocytes Langerhans cells Collage and elastin fibres
What cells make collagen and elastin in the dermis?
Fibroblasts
Why do people of colour have less pronounced photo ageing?
Greater UV protection due to a larger amount of melanin in skin keratinocytes
What are the two vascular plexuses in the dermis?
Superficial vascular plexus
Deep vascular plexus
Where do the lymphatics run in the dermis?
They follow the vascular plexuses
What is the immune functions of the lymphatics in the skin?
Immune surveillance by circulating lymphocytes and langerhans cells
Channelling of micro-organisms and toxins
What are the somatic sensory nerves in the dermis?
Free nerve endings in the high dermis
Special receptors
What are the pressure receptors in the dermis?
Pacinian bodies
What are the vibration receptors in the dermis?
Meissners corpuscles
What does the autonomic nerve supply in the dermis?
Blood vessels, nerves and glands
What are the 3 main segments of the hair follicle
Infundibulum - upper part
Isthmius - where sebaceous gland opens into the hair follicle and location of stem cells
Hair bulb - base of the follicle
What are the three types of glands in the dermis?
Sebaceous
Apocrine
Eccrine
What is the function of the eccrine gland?
True sweat gland - makes watery sweat for thermoregulation and filtration
What is the function of the sebaceous gland?
Attaches to the hair follicle making sticky oil to lubricate the hair follicle.
Hormone sensitive.
This controls moisture loss and protects from fungal infections.
What is the function of the apocrine gland?
Discharges into the hair follicle. Purpose unclear
At what age are sebaceous and apocrine glands activated?
During puberty
What are the functions of the skin?
Barrier function Metabolism and detoxification Thermoregulation Immune defence Communication Sensory functions
What is the metabolic activity of the skin?
Vitamin D metabloism
Thyroid hormone metabolism
Metabolism of chemicals, pollutants, drugs and sunlight
What does UBV convert to produce Vitamin D3?
7-dehydrocholesterol
Describe thyroid hormone metabolism in the skin?
Thyroxine –> Triiodothyronine
What is the named fascia of the upper libs?
Pectoral fascia
Deltoid fascia
Brachial fascia
Antebrachial fascia
What is the names fascia of the lower limb?
Fascia lata - thigh
Iliotibial tract
Crural fascia - leg
Where does the arterial supply to the upper limb begin?
Subclavian artery
What vessels does arterial blood flow through in the arm?
Subclavian –> brachial –> deep brachial –> radial (laterally) & ulnar (medially) –> deep and superficial palmar arches –> metacarpal and digital arteries
How many digital arteries are there per digit of the hand?
4
Where does the arterial supply to the lower limb begin?
External iliac artery
What vessels does arterial blood flow through in the leg?
External iliac artery –> femoral and deep femoral–> popliteal artery –> anterior and posterior tibial –> arteries of the foot
What are the arteries of the foot?
Medial and lateral plantar
Arcuate
Deep plantar arch
Metatarsal and digital
What are end arteries?
There is no collateral blood supply in an area
Where is the pulse of the bifurcation of the common carotid?
Anterior to sternocleidomastoid muscle at the level of the upper border of the thyroid cartilage
Describe superficial veins of the limbs
In superficial fascia
Variable patterns
Smaller and thinner
drain into deep
describe the deep veins of the limbs
Run deep to the deep fascia
More predictable pattern
Larger and thicker
Often occur in neurovascular bundles
What are the main superficial veins in the upper limbs?
Cephalic Vein
Basilic Vein
What is the median cubital vein?
A vein that is formed from the connection of the basilic and cephalic vein
What are the main superficial veins in the lower limbs?
Great saphenous vein
Small saphenous vein
What are vena comitantes?
Veins that surround the artery in a fascial sheath
Where do superficial lymphatic vessels of the upper limbs that follow the basilic vein drain to?
Cubital nodes then lateral axillary nodes
Where do superficial lymphatic vessels of the upper limbs that follow the cephalic vein drain to?
Apical axillary nodes
Where do the lymph vessels of the upper limb eventually drain to?
Subclavian nodes
What vein do the superficial lymphatics of the lower limb follow?
Saphenous veins
What are the layers of the skin at 4 weeks foetal development?
Periderm
Basal Layer
Dermis
What are the layers of the skin at 16 weeks foetal development?
Keratin Layer Granular Layer Prickle Cell Layer Basal Layer Dermis
What are corneocytes?
Terminally differentiated non-nucleated cell remnants
What is contained within the cells of the granular layer?
Keratohyalin granules containing structural filaggrin and involucrin proteins
What are odland (lamellar) bodies?
Small sub-cellular structures of size 200-300 nm that are present in the upper spinous and granular cell layers of the epidermis.
What is the function of odland (lamellar) bodies?
These act as processing and repository areas for lipids that contribute to the epidermal permeability barrier.
What characterises Langerhans cells as antigen presenting cells?
Birbeck Granule
What T cells are found in the epidermis?
CD8+ T cells
What T cells are found in the dermis?
CD8+ T cells and CD4+ T cells
What are the two main classes of CD4+ T cells?
TH1 and TH2
Where does differentiation of kerationcytes occur?
Basement membrane
What is the name of the organelle responsible for producing pigment in melanocytes?
Melanosomes
Where are langerhans cells found?
Prickle cell layer, dermis and lymph nodes
What are the two categories of nerves within the skin?
Somatic sensory
Autonomic
Name the types of cells within the dermis
Fibroblasts Mast Cells Langerhans Cells Macrophages Lymphocytes
Why do blood vessels of the skin have a higher supply than their metabolic needs?
Because they are able to lose heat energy for thermoregulation
What do lymphatic vessels drain from the skin?
Plasma proteins, extravaste cells and excess interstitial fluid
What are the two catergories of nerves within the skin?
Somatic sensory
Autonomic
What stimulates the eccrine gland?
Sympathetic nervous supply
What stimulates the apocrine gland?
The hormone, androgen
What metabolic processes is the skin involved in?
Vitamin D and thyroid metabolism and defence against chemicals etc.
What is a Skin Phototype 1?
Doesn’t Tan, burns easily
What is a Skin Phototype 2?
Goes red in the sun but turns brown after multiple exposures
What is a Skin Phototype 3?
Goes red in the sun but turns brown after one exposure
What is a Skin Phototype 4?
Tans easily, rarely burns
What is a Skin Phototype 5?
Brown Skin
What is a Skin Phototype 6?
Black Skin
What are porphyrins?
Chemicals that are essential for the function of haemoglobin. High levels of porphyrins can cause significant problems.
What is an adhesion virulence factor?
Enables binding of the organsim to host tissue
What is an invasin virulence factor?
Enables he organism to invade a host cell/tissue
What is an impedin virulence factor?
Enables the organism to avoid host defence mechanisms
What is an aggressin virulence factor?
Causes damage to the host directly
What is a modulin virulence factor?
Induces damage to the host directly
What type of bacteria are more common in skin infections?
Gram +ve - staphylococcus and streptococcus
Name two staphylococci of the skin…
S. Aureus
S. Epidermis
Name a type of streptococcus skin infection…
Streptococcus Pyogenes/Group A Streptococcus
What is the route of the cephalic vein?
It arises from the dorsal venous network and moves proximally up the lateral side of the forearm. It then moves over the midline of the biceps brachii and pierces the deep fascia at the deltopectoral triangle to drain into the axillary vein.
What is the route of the great saphenous vein?
It arrises from the medial dorsal venous arch and moves proximally up the anteriolateral aspect of the lower limb. It pierces the deep fascia in the femoral triangle and drains into the femoral vein.
What are some of the prominent virulence factors of staphylococcus aureus?
Coagulase Fibrinogen Binding Protein Haemolysis a Leukocidin TSST-1
What is the role of fibrinogen binding protein as a virulence factor?
Adhesin. blocks entrance of larger immune cells
What is the role of coagulase as a virulence factor?
Clots plasms and therefore prevents the entrance of larger immune cells
What is the role of leukocydin (PVL) as a virulence factor?
A pore-forming toxin that inactivates leukocytes
What is the role of protein a as a virulence factor?
Antiphagocytic toxin
What is the role of TSST-1 as a virulence factor?
Stimulates interleukin and TNF release to cause an overwhelming immune response
What are superantigens?
Super antigens (SAgs) are a class of antigens that result in excessive activation of the immune system e.g. TSST-1
What methods do virulence factors employ to evade host defences?
Super antigens divert the immune response to other areas
Coagulase will coagulate plasma to prevent large immune cells from getting to their point of requirement
What type of haemolysis do Group A Streptococcus undergo?
Beta haemolysis
What is the Lancefield system?
A method of further subdividing Group A streptococcus by their M protein antigens
What are some of the prominent virulence factors of streptococcus pyogenes?
Super antigenic toxins
Haemolysins (SLS) - cause tissue damage and ulcers
M proteins - bind Factor M, fibronectin, fibrinogen and albumin
What are the basic tissue groups found in the skin?
Epithelium Glands Muscle Hair Adipose Tissue Connective Tissue Nervous Tissue
What type of glands regulate heat and salt loss?
Eccrine glands
What do free nerve ending detect in the skin?
Pain
What is primary intention healing?
The edges of the wound are approximated by stitches leading to rapid healing
What is secondary intention healing?
Used for larger wounds that are too tight to stitch. This will heal naturally leaving a scar
What are the three stages of wound healing?
Inflammation
Proliferation
Tissue Remodelling
What is a genetic variation that has no effect?
Polymorphism
What is superficial fascia?
Loose connective tissue and fat that varies in depth. It contains superficial blood vessels, cutaneous nerves, lymphatics and sweat glands.
What is deep fascia?
This is present in most of the body and is deep to the skin and superficial fascia. It is composed of dense connective tissue and divides the limbs into compartments.
Describe the course of the cephalic vein…
Arises from the dorsal venous network, runs up the lateral aspect of the limb and drains into the axillary vein.
Describe the course of the basilic vein…
Arises from the dorsal venous network, runs up the medial aspect of the limb and drains into the brachial vein
What vein does the cephalic vein drain into?
Axillary vein
What vein does the basilic vein drain into?
Brachial vein
What it the median cubital vein?
connection between the cephalic and basilic vein, this is not present in all people
Describe the course of the Great Saphenous Vein…
arises from the dorsal venous arch and runs up the medial aspect of the limb. It then drains into the femoral vein within the femoral triangle
Describe the course of the Small Saphenous Vein…
arises from the dorsal venous arch and rubs up the posterior midline of the leg. It then drains into the popliteal vein, posterior to the knee
What vein does the Great Saphenous Vein drain inot?
Femoral Vein
What vein does the Small Saphenous Vein drain into?
Popliteal Vein
What is the course of the superficial lymphatics in the upper limb?
arise from the plexuses in the fingers and hand and follow the same course as the cephalic and basilic veins
What is the course of the deep lymphatics in the upper limb?
follow the deep veins pf the upper limb and drain into the lateral lymph nodes.
What is the course of the superficial lymphatics in the lower limb?
Follow the saphenous veins
What is the course of the deep lymphatics in the lower limb?
Follow the deep veins of the lower limb and drain into the popliteal lymph nodes
Where do the axillary lymph nodes drain to?
Subclavian lymphatics
Where do the external iliac lymph nodes drain into?
Common iliac nodes then the lumbar lymphatics.
Name some virulence factors associated with streptococcus pyogenes…
Superantigenic toxins
M Proteins
Haemolysin SLO
Haemolysin SLS
What are some examples of mobile genetic elements?
Plasmids
Bacteriophages
Transposons
Pathogenicity Islands
What is the breslow thickness?
The distance between the granular layer and the deepest tumour cell in melanoma
What antibiotic is given fro S. Aureus infections?
Flucloxacillin, doxycycline if penicillin allergic
What is precision medicne?
Giving patients treatment that will benefit their individual condition as opposed to treatment that is used for the patient group as a whole
What diseases are most affected by precision medicine?
It is most effective for rare, highly penetrant diseases
What type of mutation is most likely to have a multi-systemic effect?
Autosomal dominant
What is a commensal organism?
A commensal is an organism that uses food supplied in the internal or the external environment of the host, without establishing a close association with the host, for instance by feeding on its tissues.
What is a pathogenic organism?
A pathogenic organism is an organism that can cause damage to a host. This may result in illness.
How do we distinguish a commensal organism from a pathogenic organism?
Commensal organisms do not encode aggressive tools for invasion of the host.
What is a dermophyte?
A group of fungus that can cause skin infection in humans
What are some stimuli that cause mast cells to degraulate?
Allergens in a Type 1 Hypersensitivity reactions
Anti-IgE in auto immune conditions
Endogenous substances such as Substance P
Complement proteins such as C5a
Exogenous chemicals such as Codeine
What is vitamin D?
A fat soluble pro-hormone essential for calcium and phosphorus metabolism
What are the different types of vitamin D?
Vitamin D2
Vitamin D3
1,25 dihydroxycholecalciferol (calcitriol)
What is responsible for determining the skin phototype?
The amount of melanin pigment in the skin.
What is the role of keratinocytes in vitamin D metabolism?
The keratinocytes of the skin are both the primary source of vitamin D for the body and are also able to metabolise vitamin D into its active metabolite.
What is cancer?
an accumulation of abnormal cells that multiply through uncontrolled cell division and spread to other parts of the body by invasion and/or distant metastasis via the blood and lymphatic system
What are oncogenes?
over-active forms of genes that positively regulate cell division. These drive tumour formation when their activity or abundance is increased.
What are proto-oncogenes?
normal versions of these genes that have not yet been mutated.
What are tumour suppressors?
the inactive or non-functional form of a gene that negatively regulates cell division. This prevents the formation of a tumour when functioning normally.
What is the functions of tumour suppressor genes?
This can trigger cell cycle arrest for DNA repair OR can trigger apoptosis
Describe UVA…
UVA causes INDIRECT damage via oxidation. It penetrates more deeply into the skin than UVB and we are exposed to a lot more as it passes through the ozone layer easier.
Describe UVB…
UVB causes DIRECT damage to DNA. It is up to 1000x more damaging than UVA when the sun is directly overhead.
What are the two major types of UVB induced DNA lesions?
Cyclobutane pyrimidine Dimers
Pyrimidine-Pyrimidone Photo Products
What gene removes UVB induced DNA lesions?
Nucleotide Excision Repair
How does UVA cause DNA damage?
Via oxidation of DNA deoxyguanosine to form 8-oxo-deoxyguanosine
What gene repairs UVA induced lesions?
Base Excision Repair
What is hedgehog signalling?
HH signalling targets include genes that are important for cell proliferation — proto-oncogenes — as well as growth factors.
What type of cancer is malfunctioning PTCH associated with?
Basal Cell Carcinoma
What is cryotherapy?
This is a technique used for the destruction of tissue by the application of cold
What is the mechanism of cryotherapy?
- Intracellular ice formation
- Osmotic changes
- Vascular changes
- Immune system stimulation
What is the function of the melanocortin 1 receptor gene?
Determines balance of pigment in the skin and hair by converting phaeomelanin to eumelanin.
What pigment causes all hair colours other than red?
Eumelanin
What pigment causes red hair?
Phaeomelanin
