Dermatology Flashcards
1
Q
What is the epidermis?
A
Outermost layer of skin.
2
Q
Where does the epidermis originate from?
A
Ectoderm.
3
Q
What is the dermis?
A
Layer of skin inbetween basement membrane and subcutaneous fat.
4
Q
Where does the dermis originate from?
A
Mesoderm.
5
Q
How does skin development start?
A
Single layer of cuboidal cells form and make up the surface ectoderm. Secondary layer of squamous non keratinising cells form on top and these cells are know as the periderm.
6
Q
What do the periderm cells do in early skin development?
A
Secrete vernix caseosa which is a white waxy protective substance.
7
Q
What happens later on at week 11 of skin development?
A
Basal layer of cuboidal cells proliferate to form multilayer intermediate zone. Basal layer of cuboidal cells is now know as the stratum basale.
8
Q
What happens at week 20 of skin development?
A
Further differentiation forms spinosum, granulosum, lucidium and corneum.
9
Q
Where do hair follicles develop from?
A
Stratum basale.
10
Q
What are the epidermal ridges that protrude into the dermis known as?
A
Rete ridges.
11
Q
What is the superficial layer of the dermis known as?
A
Papillary dermis.
12
Q
What are the skin layers from top to bottom?
A
Epidermis, basement membrane, dermis and subcutaenous fat.
13
Q
What cells make up the epidermis?
A
Keratinocytes.
14
Q
Where does cell division occur in the skin?
A
Stratum basale.
15
Q
What are the layers of the epidermis from bottom to top?
A
Stratum basale, stratum spinosum, stratum granulosum, Stratum lucidum and stratum corneum.
16
Q
What occur as you go up the layers of the epidermis? And why is this a problem in some diseases?
A
Differentiation and flattening of cells. This process can be accelerated in skin diseases such as psoriasis.
17
Q
Why is the stratum lucidum different from other epidermal layers?
A
Only present in palms and soles.
18
Q
Describe the stratum corneum?
A
Outermost layer of the epidermis. Contains no nuclei or organelles.
19
Q
Describe the stratum lucidum?
A
Only present in palms and soles. No nuclei or organelles.
20
Q
What does the keratinocyte cytoskeleton contain?
A
Actin containing microfilaments. Tubulin containing microtubules. Intermediate filaments which are the keratins.
21
Q
Functions of keratins?
A
Structural properties. Cell signalling. Wound healing.
22
Q
What are between keratinocytes?
A
Tight junctions, adherens junctions, demosomes, gap junctions.
23
Q
What is the function of desmosomes?
A
Major adhesion complex. Anchor intermediate filaments to cell membrane and bridge adjacent keratinocytes. Provide strength.
24
Q
What are gap junctions and what do they do?
A
Contain intercellular channels. Form connections between cytoplasm of adjacent keratinocytes.
25
What complex/junction inbetween keratinocytes are essential for cell synchronization and metabolic coordination?
Gap junctions.
26
What are adherens junctions and what do they do?
Transmembrane structures that engage with the actin skeleton.
27
What do tight junctions do?
Role in barrier integrity and polarity.
28
What epidermal cells other than keratinocytes are present?
Melanocytes, langerhans cells, merkel cells and mast cells.
29
Describe melanocytes
Dendritic cells that distribute melanin pigment to keratinocytes.
30
What are melanocytes derived from?
Neural crest.
31
What results in different skin colours?
Amount of melanin produced varies. Number of melanocytes are the same.
32
What are langerhans cells?
Dendritic antigen presenting cells.
33
What are merkel cells?
Mechanosensory receptors.
- involved in sensation.
34
What does the basement membrane contain?
Collagens, laminin and integrins.
35
What are the most prominent types of collagen in the basement membrane?
IV, VII
36
What is the function of the basement membrane?
Cell adhesion, gate keeping functions for cell migration and diffusion of molecules. Presence of rete ridges.
37
Function of rete ridges?
Strength and provides specialised environment for epidermal stem cells.
38
What is the dermis and what is its function?
Extracellular matrix that provides strength.
39
What are the two main layers that make up the dermis?
Papillary dermis and reticular dermis.
40
Describe the papillary dermis
Superficial layer of the dermis that is made up of connective tissue and is highly vascular.
41
Describe the reticular dermis
Dense connective tissue that forms bulk of dermis.
42
What proteins does the dermis contain?
Collagen, fibrillin and elastin.
43
What glycoproteins does the dermis contain?
Fibronectin, fibulin and integrins.
44
What do the glycoproteins in the dermis do?
Facilitate cell adhesion and cell motility.
45
Where is the ground substance located in the dermis?
Between dermal collagen and elastic tissue.
46
What makes up the ground substance?
Glycosaminoglycans and proteoglycans.
47
What is the primary cell in the dermis?
Fibroblasts.
48
What other cells apart from fibroblasts are present in the dermis?
Mast cells, neutrophils and lymphocytes.
49
Where is the skin blood supply present?
Dermis. Does not cross into epidermis.
50
Eccrine vs apocrine sweat glands?
Eccrine secrete directly onto skin surface while apocrine secrete into hair follicle.
51
What stimulates eccrine sweat glands?
Cholinergic nerves and adrenergic nerves.
52
What stimulates apocrine sweat glands?
Adrenergic nerves.
53
What is the pilosebaceous unit made up of?
Hair follicle, hair shaft and sebaceous gland.
54
What is the function of the arrector pili muscle?
Arrector pili muscle is connected to the hair follicle. Contraction of the muscle causes hair erection and goosebump.
55
Where are most skin nerves found?
Superficial dermis.
56
Where are encapsulated receptors found?
In the dermis.
57
Where are non encapsulated receptors found?
Epidermis.
58
Describe the meissner's corpuscle?
Encapsulated, unmyelinated mechanoreceptor present in the superficial dermis. Most concentrated in thick hairless skin.
59
What is the meissner's corpuscle responsible for?
Light touch and slow vibration.
60
Describe the ruffini corpuscle
Encapsulated mechanoreceptor. High density around fingernails.
61
What is the ruffini corpuscle responsible for?
Sensitive to skin stretch to monitor slippage of objects.
62
Describe the pacinian corpuscle
Encapsulated rapidly adapting mechanoreceptor.
63
What is the pacinian corpuscle responsible for?
Surface texture - deep pressure and vibration.
64
Describe the merkell cell
Non encapsulated mechanoreceptor that is a modified epidermal cell.
65
What is the merkell cell responsible for
Light sustained pressure.
66
Functions of the skin
Immunological barrier, physical barrier, thermoregulation and provides metabolic functions.
67
How do langerhans cells detect pathogens?
Use TLRs to detect PAMPS. This results in activation of innate immune system and induction of adaptive response.
68
What do langerhans cells do in absence of danger?
Promote expansion and activation of Tregs.
69
What do langerhans cells migrate through?
Tight junctions.
70
What immune cells are present in the skin?
Tissue resident T cells, macrophages and dendritic cells .
71
How are keratinocytes involved in immunity?
Produce antimicrobial peptides.
72
How does the skin behave as a physical barrier?
Cornified envelope prevents water and protein loss from skin. Subcutaneous fat prevents damage from trauma. Melanin produced protects DNA damage from UV.
73
How does the skin regulate temperature?
Vasodilation or vasoconstriction in deep or superficial vascular plexuses. This regulates heat loss. Eccrine sweat glands provide cooling effect.
74
What other role do eccrine sweat glands have?
Fluid balance.
75
How does the skin have metabolic functions?
Vitamin D3 synthesis. Subcutaneous fat provides calorie reserve and produces leptin.
76
What function does hair have?
Thermoregulation, source of epithelial and melanocyte stem cells, production of apocrine sweat, production of sebum.
77
What are the coarse thick hairs present in the scalp, eyebrows and eyelashes called?
Terminal hairs.
78
What are the fine shorts hairs found on arms and legs called?
Vellus hair.
79
What are the 3 phases of hair growth?
Anagen, catagen, telogen.
80
What happens during the anagen phase?
Hair growth.
81
What happens during the catagen phase?
Blood supply withdrawn. Hair follicle shrinks. Growth stops.
82
What happens during telogen phase?
Resting phase where hair is eventually lost.
83
Why is the sebaceous gland described as a holocrine gland?
Sebocytes release their content by rupture of the cell membrane.
84
What are the two regions of hair called?
Infundibulum and isthmus.
85
Describe the infundibulum
Uppermost portion of hair from sebaceous gland to surface of skin.
86
Describe the isthmus
Lower portion between sebaceous gland and arrector pili muscle
87
Process in which hairs are produced?
Trichilemmal keratinization. From keratinocytes to keratin.
88
What does the bulge contain and why is this important?
Contains hair follicle stem cells. Can migrate downwards to form hair follicle or upwards to form sebaceous glands or heal wounds.
89
What does the outer root sheath contain?
Stem cells.
90
What does the inner root sheath contain?
Encloses nerve fibers and capillaries.
91
What does the inner root sheath do?
Shapes hair.
92
What are the functions of nail?
Protection of distal phalanx and increases dexterity.
93
What is the nail plate firmly attached to?
Nail bed.
94
Where does the nail plate detach?
Hyponychium
95
Where does the nail plate emerge from?
Proximal nail fold.
96
What produces the nail plate?
Nail matrix.
97
What is the visible portion of the nail matrix called?
Lunula.
98
How is the nail plate produced?
Keratinocytes in the nail matrix lose their nuclei and cytoplasm and become keratin.
99
Where is the nail matrix?
Above distal bone and below proximal nail fold.
100
Description of psoriasis?
Chronic immune mediated disorder that produces scaly plaques.
101
What else can psoriasis cause?
Psoriatic arthritis.
102
Psoriasis disease mechanism
Keratinocytes release DNA/RNA which form complexes with antimicrobial peptides. This activates dermal dendritic cells which migrate to lymph nodes to active th1/th17/th22 cells. This results in a chemokine release (migration of other immune cells) and cytokine release. Increased keratinocyte proliferation results in psoriatic plaque.
103
What lifestyle changes can help manage psoriasis?
Reducing alcohol consumption and smoking.
104
What is the first step management to treating psoriasis?
Topical therapies and phototherapy.
105
What topical therapies can be given for psoriasis?
Vitamin D analogues with corticosteroid. Retinoids. Tacrolimus.
106
Why can tacrolimus be a better option compared to corticosteroids?
Tacrolimus is a calcineurin inhibitor and so is not a steroid. Steroids can cause skin thinning
107
Types of phototherapy that can be used for psoriasis?
Narrowband UVB. PUVA (psoralen - makes skin sensitive to UVA. UVA is then given).
108
What is the advantage of using narrowband UVB over PUVA?
Lower risk of skin cancer with narrow band UVB.
109
In severe or widespread psoriasis what treatment would you offer?
Phototherapy or systemic therapies such as methotrexate or ciclosporin.
110
What oral retinoid can you give for psoriasis?
Acitretin
111
What advanced therapies can you offer for psoriasis?
PDE4 inhibitors, biologics and JAK inhibitors.
112
Give an example for a biologic that can be used for psoriasis?
Anti TNF gamma.
113
Description of atopic eczema
Chronic inflammatory condition that is a pruritic condition.
114
When does atopic eczema usually begin?
Infancy or childhood.
115
What are the two principle mechanisms that cause eczema?
Barrier defect and immune dysregulation.
116
What causes a barrier defect in atopic ecezema? How does this cause the barrier deffect?
Defect in filaggrin.
Defect in filaggrin results in increased transepidermal water loss due to loss of extracellular lipids and impaired ceramides.
This results in impaired protection against microbes and allergens.
117
What is filaggrin responsible for?
Binds and aggregates keratin bundles and intermediate filaments in stratum corneum.
118
How does dysregulation of immune system lead to atopic eczema?
S.aureus stimulates th2 response and inhibits treg cells. Presence of eosinophils as well.
119
What causes eczema herpeticum?
Herpes simplex virus.
120
How do you treat eczema herpeticum and how do you not treat it?
Treat it using acyclovir. Use of corticosteroids can make it worse.
121
How do you manage atopic eczema?
Use of emollients and patch testing (to test for allergens).
122
First stage treatment for atopic eczema?
Corticosteroids and tacrolimus. - topical treatment
UVB or PUVA - phototherapy
123
Steroid ladder for atopic eczema? (second stage treament)
Hydrocortisone, clobetasone, betamethasone, mometasone, clobetasol.
124
Side effects of using steroids for atopic eczema?
Folliculitis or acne.
125
Immunosuppressive drugs for atopic eczema?
Methotrexate or ciclosporin.
126
What biologics can be used for eczema?
TH2 cytokines
anti IL-4
anti IL-13
127
What else apart from biologics could be used for atopic eczema?
JAK inhibitors.
