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Dermatology > Structure and function of skin > Flashcards

Structure and function of skin Flashcards

1
Q

What are the 2 layers of skin?

A

Epidermis - striatified squamous epithelium

Dermis - connective tissue

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2
Q

What is the embryological origin of the epidermis?

A

Ectoderm cells form a single layer periderm

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3
Q

What is the embryological origin of the dermis?

A

Formed from the mesoderm below the endoderm

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4
Q

What is the embryological origin of melanocytes?

A

Pigment producing cells from the neural crest

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5
Q

What are blaschko’s lines?

A

Developmental growth pattern of skin that doesn’t follow vessels, nerves or lymphatics

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6
Q

What is an epidermal nevus?

A

A benign harmatomatous growth following a linear arrangement that follows the lines of Blaschko

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7
Q

What are the appendages of the skin?

A

Nails
Hair
Glands
Mucosae

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8
Q

How is skin able to move so freely?

A

The dermis sits on the sub-cutis which is a rolling sheet of fat alowing movement

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9
Q

What is a sebaceous gland?

A

A small gland in the skin which secretes a lubricating oily matter into the hair follicles to lubricate the skin and hair

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10
Q

What cell type is the epidermis made up of

A

Keratinocytes

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11
Q

How many layers make up the epidermis?

A

4 layers

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12
Q

What other cells are situated within the epidermis?

A

Melanocytes
Langerhans
Merkel

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13
Q

What are the 4 layers of the epiderm?

A

Basal layer (ectoderm)
Prickle cell layer
Granular layer
Keratin layer

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14
Q

What is an apocrine gland?

A

Present in armpits, groin and are around nipples

Scent glands that secrete an odor

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15
Q

What regulates epidermal turnover?

A

Growth factors
Cell death
Hormones

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16
Q

What conditions can arise due to a loss of control in epidermal turnover?

A 
Skin cancer (malignant) 
Psoriasis (benign)
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17
Q

Why is psoriasis red in appearance?

A

Blood vessels move closer to the surface of the skin

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18
Q

How many days does it take a keratinocyte to move from the basal cell layer to the keratin layer?

A

28 days

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19
Q

What are the characteristics of the basal layer?

A

One cell thick
Small cuboidal
Intermediate filaments (keratin)
Highly metabolically active

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20
Q

What are the characteristics of the prickle cell layer?

A

Larger polyhedral cells
Lots of desmosomes
Intermediate filaments connect to desmosomes

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21
Q

What are the characteristics of the granular cell layer?

A 
2/3 layers of flat cells 
Contain large keratohyalin granules 
Odland bodies 
High lipid content
Origin of cornified envelope
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22
Q

What do the keratohyalin granules contain?

A

Filaggrin and involucrin

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23
Q

What is a corneocyte?

A

Lipids and proteins from the burst granular cell

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24
Q

What are the characteristics of the keratin layer?

A

Made up of corneocytes, keratin and filaggrin

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25
What does filaggrin do?
Attracts and traps water creating not only a tight waterproof barrier but providing moisture to the skin (without you get eczema)
26
What is the cornified envelope?
Sheath made from protein and lipids
27
Where are there mucosal membranes?
Eyes, mouth, nose, genito-urinary and GI tracts
28
What are some specialisations in the oral mucosa?
Keratanised in hard palate to deal with pressure | Tonge papillae
29
What are some specalisations in the ocular mucosa?
Lacrimal glands Eye lashes Sebaceous glands
30
What is the embryological origin of melanocytes?
Migrate from neural crest to the epidermis in first 3 months of foetal development
31
What do melanocytes produce?
Pigment producing dendritic cells
32
What organelles do melanocytes contain?
Melanosomes
33
What is the function of melanosomes?
Convert tyrosine to melanin pigment
34
What are the different types of epidermal cells?
Keratinocytes Melanocytes Langerhans Merkel cells
35
What embryological structure is dermis derived from?
Mesoderm
36
What embryological structure is epidermis derived from?
Ectoderm
37
What is the function of melanin?
Absorbs light (natural density filter)
38
What happens to full melanosomes?
They are transferred to adjacent keratinocytes via dendrites to form a protective cap over the nucleus
39
What is the pathogenesis of vitiiligo?
The melanocytes are attacked by T cells
40
What is the pathogenesis of albinism?
Genetic partial loss of pigement production
41
What is nelson's syndrome?
Melanin stimulating hormone is produced in excess by the pituitary causing hyperpigmentation
42
What is a malignant melanoma?
A tumour of the melanocyte cell line
43
What embryological structure do langerhans cells arise from?
Mesenchymal origin - bone marrow
44
Where are langerhans cells found in the epidermis?
Prickle cell level in the epidermis Dermis Lymph nodes
45
What is the function of langerhans cells?
Antigen presenting cells | Pick up antigens in skin and circulate to lymph nodes via lymphatic system
46
Where are merkel cells found?
In the basal layer between keratinocytes and nerve fibers
47
What is the function of merkel cells?
Mechanoreceptors essential for light touch sensation
48
Where does the pilosebaceous unit originate from?
Grows out of the basal layer with an adjacent sebaceous gland
49
How is hair pigmented?
Via melanocytes above the dermal papilla
50
What are the phases of growth for hair?
``` Anagen = growing Catagen = involuting Telogen = resting ```
51
What are the different types of hair follicles?
Lanugo (in utero) Vellus Terminal
52
What can cause hirsutism?
Polycystic ovaries - too much testosterone
53
What causes alopecia areata?
Autoimmune hair loss as hair follicle cells are attacked by T lymphocytes
54
How do nails grow?
Stem cells in basal layer but instead of becoming prickle cells they enter a different differentiation program and start to form flat cells that produce keratin
55
Where does nail growth start?
Nail matrix
56
What is the dermo-epidermal junction?
Inferface between epidermis and dermis
57
What is the function of the dermo-epidermal junction?
Support, anchorag, adhesion, growth and differentiation of basal cells Semi-permable membrane acts as a barrier and filter
58
What makes up the dermo-epidermal junction?
Lamina lucida Lamina densa Sub-lamina densa zone
59
What is bullous` pemphigoig?
An autoimmune skin disease, involving the formation of blisters at the space between the epidermis and dermis skin layers. It is a type II hypersensitivity reaction, with the formation of anti-hemidesmosome antibodies
60
What is epidermolysis bullosa?
A group of genetic conditions that result in easy blistering of the skin and mucous membranes. Blisters occur with minor trauma or friction and are painful
61
What cells make up the dermis?
Mainly ground substance | Fibroblasts, macrophages, mast cells, langerhans cells, lymphocytes
62
What do fibroblasts produce?
Collagen and elastin
63
What is present in ground substance?
Glycosaminoglycans
64
Why is there a greater blood supply than needed for the skin?
Thermoregulatory processes
65
How do the blood vessles form in the skin?
Horizontal plexuses
66
What blood vessels supply the hair follicle?
Deep vascular plexus
67
What blood vessels supply the epidermis?
Papillary dermis
68
What is angiomia?
Overgrowth of blood vessles | Benign
69
What nerves are present in the skin?
Somatic sensory (dermatomes): Free nerve endings Autonomic nerve supply - blood vessels, nerves and glands
70
What are the special receptors present in the skin?
Pacinial corpuscle | Meissners corpuscle
71
What nerve supply do the sebaceous glands have?
Autonomic supply
72
What do the pacinal corpsucle detect?
Deep pressure - found deep in the dermis
73
What do meissner's corpscule detect?
Touch and vibration
74
What do pacinial corpuscles look like histologically?
Onion rings
75
What is a neurofibromatosis?
Overgrowth of nerve endings causing multiple tumours | Linked to underlying CNS tumours
76
What are the 3 different types of skin glands?
Sebaceous Apocrine Eccrine
77
What do sebaceous glands produce?
Sebum - squalene, wax esters, TG and FFA
78
What is the function of sebaceous glands?
Control moisture loss | Protect from funal infections
79
What is the treatment for acne vulgaris?
Topical retinoids Antibiotics Roaccutane
80
What and where are the apocrine sweat glands?
Axillae and perinuem Androgen dependent Produce oily fluid that has an odor after bacterial decomposition
81
What and where are eccrine sweat glands?
Whole skin surface | Cool by evaporation, moisten palms
82
What is the nerve supply to eccrine glands?
Sympathetic nerve supply
83
What is the function and consequence of failure of the barrier of skin?
Fluid loss leads to dehydration Protein loss leads to hypoalbuminaemia Infection
84
What is the function and consequence of failure of the thermoregulation of skin?
Heat loss leads to hypothermia
85
What is the function and consequence of failure of the immune defence of skin?
Spread of infection
86
What is the function and consequence of failure of the metabolic function of skin?
Disordered thyroxine metabolism
87
What is the function and consequence of failure of the communication function of skin?
Inability to display healthy skin is a stigma
88
What is the function and consequence of failure of the sensation of skin?
Pain sensation working lead to pain
89
What is an example of a barrier failure disease?
Steroid-sulphatasae deficiency X-linked ichythosis Not normal lipid distribution in keratin layer Cumulative irritant hand dermatitis
90
What does the skin aid metabolism of?
Vitamin D | Thyroid hormone
91
What is a disease example when the skin's immune defence is inadequate?
Crusted scabies | Tuberculoid leprosy
92
What is a granuloma?
Specialized macrophages (anitchov cells) around a core of fibrinoid collaged necrosis. Aschoff cells are interspersed between other cells while lymphocytes make up the outer layer
93
What is eczema herpeticum?
Disseminated herpes simpex virus infection
94
What is the definition of stigma?
Situation of an individual who is disqualified from full social acceptance
95
What is a ruffini ending?
Slowly adapting mechanoreceptor responsible for the sensation of the stretch of your skin, sustained pressure on skin and perception of heat
96
What is a hair follicle?
An invagination of the epidermis
97
What is contained within the central medulla?
Soft heratin
98
What is contained within the outer cortex?
Hard keratin
99
What is the papilla?
Contains multiple vascular channels
100
What does the matrix region contain?
Keratin producing cells
101
What is the hypochium?
Secures the free nail edge
102
What is seen histologically in acute dermatitis?
Intra-epidermal vesicles containing white cells and cell debris Intracellular oedema called spongiosis
103
What is seen histologically in psoriasis?
Parakeratosis Micro-abscesses Elongated rete pegs
104
What is seen histologically in normal skin from the sole of the foot?
Thick keratin layer Prominent granular layer Irregular DEJ Eccrine sweat gland duct
105
What is seen histologically in bullous pemphigoid?
Fluid filled bulla with eosinophils
106
What it toxic epidermal necrolysis?
Drug induced, keratinocyte death resulting in epidermal detachement at the DEJ
107
What are the 3 stages to wound healing?
Inflammation Proliferation and tissue remodelling Tissue remodelling
108
What occurs during the inflammation phase of wound healing?
Platelets form the initial clot and release inflammatory mediators Leucocytes debride the wound bed by phagocytosing bacteria and scavenging cellular debris Inflammation gradually decreases as keratinocyte proliferation and new tissue formation becomes predominant
109
What occurs during the proliferation and tissue remoddeling phase of wound healing?
Cells divide to re-epithelialise the wound surface Granulation tissue formation is stimulated Fibroblasts lay down matrix and contract the wound (fibroplasia) Endothelial cells develop into new blood vessels (angiogenesis) New tissue formed
110
What occurs during the tissue remoddeling phase of wound healing?
New tissue converted to mature scar tissue | Fibroblasts lay down collagen to improve strength of scar and restore normal dermal matrix
111
What is primary intention wound healing?
Acute wound closed by approximating wound edges
112
What is secondary intention wound healing?
An acute wound is left to heal on its own
113
What should you consider in delayed wound healing?
``` Infection Poor arterial blood supply Poor nutrition Impaired venous return Repeated traume Systemic disease - diabetes, anaemia ```

Dermatology (24 decks)

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