ToB - Skin Flashcards

0
Q

What epithelia are on the epidermis of he skin and what are they made of?

A

Stratified squamous keratinised epithelia made from keratinocytes and their products.

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1
Q

What are the 4 layers of the epidermis?

A

1) . Stratum corneum
2) . Granular layer
3) . Prickle cell layer
4) . Basal layer

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2
Q

What cells are present in the epidermis and where?

A

1) . Melanocytes
- produce melanin from melanosomes
- dendritic cells of neural crest origin
- occur at intervals through basal layer

2) . Langerhan cells
- present antigens to T lymphocytes in allergic reactions
- are dendritic cells of bone marrow origin
- scattered through the prickle cell layer

BOTH ARE HARD TO SEE

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3
Q

How are the skins layers formed?

A

1) . Mitosis of keratinocytes in basal layer pushes new keratinocytes into prickle cell layer.
2) . These prickle cells are now joined via desmosomes = connects cells keratin to form intercellular junctions.

3) . Keratinocytes differentiate
- -> can no longer divide
- -> produce keratin

4) . In granular layer, phospholipase breaks down cell membrane of keratinocytes = differentiate to form corneocytes.
5) . Stratum corneum is formed from flattened corneocytes.

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4
Q

What are the features of corneocytes in stratum corneum?

A

Flattened
No nuclei
Mostly keratin

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5
Q

How long does it take for a cell in the basal layer to be sloughed off from skin?

A

30-40 days

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6
Q

What are the disorders of the epidermis?

A

1) . Psoriasis - extreme proliferation of basal layer and therefore all layers thicken.
2) . Vitiligo - autoimmune attack on melanocytes = depigmentation
3) . Malignant melanoma - malignant growth of the melanocytes (poor prognosis if it penetrates the basal layer) which is more common in whites than blacks as melanosomes break down easier.
4) . Allergic contact dermatitis - mediated by Langerhan cells, often in response to nickel.

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7
Q

How is the dermoepidermal junction best seen?

A

Using PAS stain

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8
Q

What is the dermoepidermal junction?

A

The epidermal basement membrane which joins the dermis and epidermis.

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9
Q

What are the skins functions?

A

1) . Barrier
- water and microbe proof
- needs overcoming for pharmaceutical cream
- disrupted by disease
2) . Psychosexual communication
3) . Sensation
- affected by leprosy and diabetic neuropathy
4) . Thermoregulation
- vascular thermoregulation
- eccrine sweating
- psoriasis can cause permanent dilation

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10
Q

What is the dermis made mostly of?

A

Extracellular matrix

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11
Q

What does the extracellular matrix of the dermis contain?

A

1) . Nerves
2) . Collagen
3) . Elastin
4) . Blood and lymphatic vessels
5) . Mast cells

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12
Q

What gives straie and solar elastosis in the skin?

A

Damage to the collagen or elastin in the dermis of the skin by UV light.

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13
Q

What is a port wine stain?

A

Where blood vessels are permanently dilated

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14
Q

Where are mast cells found and what do they contain?

A

Found surrounding blood vessels and contain granules of histamine, which are activated by allergic reactions
= local oedema due to increased vascular permeability
= urticaria
= angio-oedema

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15
Q

What is the extracellular matrix of the dermis formed by?

A

Synthesised by fibroblasts

16
Q

What sizes are the blood vessels found in the dermis?

A

Smaller in the superficial dermis, larger as you go deeper

17
Q

How are scars formed?

A

By the synthesis of collagen from fibroblasts. If excess is produced, keloids form.

18
Q

What are the appendages of the skin?

A

1) . Nails
- mostly keratin
2) . Apocrine sweat glands
- wider lumen than eccrine sweat glands
- no specific function
- secrete odourless liquid from armpits, genitalia, sub mammary glands
3) . Eccrine sweat glands
- secrete water onto skins surface for latent heat evaporation = cooling.
4) . Pilosebaceous unit
- sebaceous gland feeds sebum onto hair shaft via holocrine secretion

19
Q

What are disorders of the skins appendages?

A

1) . Acne
- abnormal differentiation of the sebaceous gland ducts
- increased sebum production can get infected.

2) . Hyperhydrosis
- excessive sweating, often from palms

20
Q

What adaptation do epithelial cells have that aid sweat glands?

A

Myoepithelial cells = have actin filaments so can contract to push sweat out.

21
Q

What is alopecia areata?

A

An autoimmune attack on the hair follicles

22
Q

What are the macroscopic differences in people’s skin and how does it vary?

A

Colour - site, ethnicity, exposure to UV light
Hair colour - site, age, ethnicity
Wrinkling/laxity - site, age, exposure to UV light

THESE CAN INFLUENCE SUSCEPTIBILITY TO DISEASE