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Structure and function Flashcards

1
Q

What ratio of GP appointments are concerned with skin?

A

1:5

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2
Q

Name the outer layer of the skin

A

Epidermis

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3
Q

What is the second layer of the skin called?

A

Dermis

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4
Q

What type of cell is the epidermis made of?

A

stratified squamous epithelium

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5
Q

What is the dermis made up of?

A

Connective tissue

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6
Q

Embryologically, where does the epidermis come from?

A

The ectoderm forms a single layer of periderm

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7
Q

Embryologically, where are melanocytes produced from?

A

The neural crest, adjacent to the neural tube.

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8
Q

Between 4 and 16 weeks gestation what does the periderm separate into?

A

The keratin layer
The granular layer
The prickle cell layer

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9
Q

What are Blaschko’s lines?

A

Developmental growth pattern of skin

Looks like dermatomes but do not confuse the two!

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10
Q

Name the layers of the skin

A

Epidermis- made up of the keratin layer, granular layer, prickle cell layer and basal layer.
Appendages - nail, hair, glands
Dermis
Sub-cutis

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11
Q

What cell primarily makes up the epidermis?

A

keratinocytes

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12
Q

Where are keratinocytes produced?

A

The basal layer of the epidermis

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13
Q

What is normal epidermal turnover time?

A

50 days

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14
Q

Name a part of the body where the epidermal layer is thicker

A

Sole of the foot or palm of the hand

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15
Q

Epidermal cell turnover is not controlled in psoriasis. Is the turnover time less or more?

A

Less
Around 4-5 days.
Normal migration from basement membrane to the keratin layer is around 28 days.

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16
Q

What is keratinisation?

A

Process of differentiation to produce a surface layer or stratum corneum

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17
Q

Describe the basal layer

A 
1-3 cells thick
Small cuboidal
lots of keratin filaments
Highly metabolically active
Melanocytes
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18
Q

What is the prickle cell layer made of?

A

Larger polyhedral cells
Lots of desmosomes
Intermediate filaments which connect to desmosomes

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19
Q

What is in the granular layer?

A

2-3 layers of flatter cells
Odland bodies.
No cell nuclei at this layer - cells start to die.
Cornified cell envelope- barrier functions

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20
Q

What is an Odland body?

A

Contain lipids and enzymes which are discharged and act as glue between intercellular spaces between the granular layer and the keratin layer.

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21
Q

What is in the keratin layer (or horny layer)?

A

Corneocytes - overlapping non-nucleated cell remnants ( also called stratum corneum)
Forms a tight waterproof barrier

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22
Q

How does HPV affect the skin?

A

Causes warts

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23
Q

Where do melanocytes come from?

A

Migrate to the epidermis from the neural crest in first 3 months of gestation

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24
Q

What do melanocytes do?

A

They live in the basal layer and above ( only epidermis) and are pigment producing dendritic cells.
Transfer melanin to adjacent cells.

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25
What organelles do melanocytes contain?
Melanosomes
26
What do melanosomes do?
Convert tyrosine to melanin pigment. | Either eumelanin in black or brown hair or phaeomelanin in red or blonde hair.
27
What does melanin do?
Stimulated by UV light- the more UV light the more melanin. Positive feedback. Acts as a barrier to protect cell nuclei from UV light. (therefore no cells with nuclei above where melanocytes are present)
28
Why are people with darker skin less likely to develop skin neoplasms?
Melanosomes are larger so cover a bigger area, remain separate as opposed to forming complexes, like in white skin.
29
What is vitiligo?
an autoimmune disease, involved with the loss of melanocytes - skin appears whiter than usual. more noticable in people of darker skin.
30
What is albinism?
Affects 1:20,000 partial loss of pigment production. Because of this neoplasms are more likely since nuclei are not protected.
31
What is Nelson's syndrome?
The hormone which stimulates eumelanin production is in excess due to a fault in the pituitary gland so the patient complains of unusually dark skin
32
What is a malignant melanoma?
A tumour of the melanocyte cell line
33
What is a Langerhans cell?
Recognises antigen-presenting cells. Sticks to and circulates to lymph nodes. Found in prickle cell level in epidermis. Also found in dermis.
34
What is a merkel cell?
Mechanoreceptors. | Found between keratinocytes and nerve fibres.
35
What is merkel cell cancer?
``` Very uncommon. Abnormal division of merkel cells. Red/purple lumps on skin Not usually painful but can develop into ulcers Prognosis is dull ```
36
What is a hair follicle made up of?
Dermal papilla with an epidermal component. Adjacent sebaceous gland. Hair is pigmented via melanocytes above dermal papilla.
37
Name the phases of growth hair follicles go through
Anagen - active growth Catagen - transitional phase Telogen - rest phase
38
What are the three types of hair?
Lanugo - in utero only - sheds before 8 months gestation Vellus - fine hair which covers most of the body Terminal - developing after puberty, aided by androgens.
39
What shape is caucasian hair?
Elliptical shape - except pubic, beard and eyelash hairs which are always oval.
40
Explain the importance of hair follicles having independent cycles ( being asynchronous)
If all hairs grew and subsequently shed at the same time we would go bald!
41
Describe male pattern hair loss
Change of hair from terminal to villus
42
Why does hair go grey (canities) ?
Reduction in amounts of tyrosinase activity which means less melanin can be produced.
43
What is virilisation?
Hirsituism in females due to excess androgen from a tumour
44
What is alopecia areata?
Autoimmune disease which causes hair loss. | Hair will first go back looking grey.
45
What protein is missing in eczema?
Filaggrin
46
HPV is common in who?
Children under 6
47
How does a wart change the skin structure?
?
48
What is scar tissue?
Defined as loss of skin appendages
49
Which organelle creates melanosomes?
Golgi apparatus
50
Birbeck granules are found in which cells?
Langerhans cells.
51
What happens when merkel cells are found in abundance?
Higher sensitivity to touch since merkel cells are mechanoreceptors
52
Which common disease affects the myelin sheath of nerve fibres?
Diabetes therefore parathesia or dysthesia. | Excess glucose disrupts proteins.
53
What does increased sebum. blocked sebaceous ducts and increased bacterial activity result in?
Acne
54
How long is the anagen phase?
between 1-8 years
55
Male pattern balding starts at what part of the scalp?
Vertex
56
What is a hair transplant?
Removal of hair from hair line posteriorly, to the vertex by punch biopsy.
57
Which nails grow faster: fingers or toes?
Fingers
58
Where do stem cells live in the nail?
In the nail matrix, just under the cuticle
59
Why is the nail red and the lunula white?
Lunula is thicker. | Blood vessels seen more easily in nail
60
Where is the dermo-epidermal junction?
Between the epidermis and the dermis
61
What is the dermo-epidermal junction's role?
Support, anchorage, adhesion, growth.
62
What is epidermolysis bullosa?
It is an inherited disease which results in a fragile dermo-epidermal junction.
63
What are the two forms of epidermolysis bullosa?
simplex (collagen or protein issue) and dystrophica ("mitten deformity" in hands and feet")
64
What is pemphigoid
An acquired auto-immune disease to the proteins in the DEJ. Skin biopsy then it can be diagnosed as a positive immunofluorescence on histology. Controlled with steroids.
65
in the dermis, what do fibroblasts do?
Secrete collagen (tensile strength) and elastin
66
In the dermis, what do Langerhans cells do?
antigen presentation
67
What is an angioma?
Tumour of vascular tissue. | Dilated vascular spaces make the mark look red.
68
What is a haemangioma?
A strawberry birthmark. Normally found in infants. Treated with beta blockers.
69
Where are the lymphatics in the skin?
Sub-epidermal
70
What are pacinian corpuscles?
receptors which detect pressure (P for Pressure) | On staining, they look like an onion cut in half
71
What are meissners corpuscles?
Receptors which detect vibration
72
What kind of nerve supply does the skin have?
Autonomic
73
What is neurofibromatosis?
When tumours grow along the nerve which is abnormally thickened. Benign.
74
What is an eccrine gland?
Covers the whole skin surface Sympathetic cholingeric supply. Purpose: heat control. "Hot day" sweating.
75
What is an apocrine gland?
Mostly found in the axilla and perineum. | Androgen dependent and emit pheromones.
76
What is a sebaceous gland?
Part of the pilosebaceous unit- includes the hair. Largest glands on face and chest. Hormone sensitive so "dormant" pre-puberty. Produces sebum
77
What is erythroderma?
widespread (80/90%) redness of skin
78
In what way is the skin metabolically active?
Metabolises vitamin D with help of UV light | Metabolises thyroid hormone (T4)
79
Where is vitamin D stored?
In the liver as 2hydroxycholecaliferol
80
What is vitamin D converted to in the kidney?
1,25 dihydroxycholecaliferol.
81
What is thyroxine (T4) converted to in the skin?
Tri-iodothyronine (T3)
82
Which is the most metabolically active layer of the skin?
Basal layer
83
At what stage in foetal development is the skin complete?
6 months
84
What is the hyponychium?
Area of skin underlying the edge of the nail

Dermatology (19 decks)

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