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Dermatology > Structure And Function Of The Skin > Flashcards

Structure And Function Of The Skin Flashcards

1
Q

Name and describe the layers of the skin

A

Epidermis- thin outermost layer
Dermis- forms connective tissue beneath the epidermis
Hypodermis/subcutis- fat beneath dermis, pigment producing cells from neural crest

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2
Q

What is the appendage?

A

Nails, hair, glands, mucosa

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3
Q

Embryology- what does the epidermis rise from?

A

The ectoderm (outermost cell layer in embryo)

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4
Q

Embryology- what does the dermis develop from?

A

Mesoderm- middle layer of embryo

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5
Q

Embryology- what does the subcutis rise from?

A

Mesoderm

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6
Q

Embryology- what does the appendages rise from?

A

Ectoderm

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7
Q

What are the key stages of foetal skin development?

A

Week 4
Week 16
Week 26

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8
Q

What happens at week 4 of foetal skin development?

A

Formation of:
Periderm
Basal layer
Dermis (corium)

Melanocytes begins to migrate from neural crest to basal layer

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9
Q

What happens at week 16 of foetal skin development?

A
  • Keratin Layer (KL)
    • Granular Layer (GL)
    • Prickle Cell Layer (PL)
    • Basal Layer (BL)
    • Dermis (D)
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10
Q

What happens at week 26 of foetal skin development?

A

Epidermis fully formed with all layers, melanocytes are now in basal layer

Sebaceous glands developed

Arector pili muscles (those that cause hair to stand up) are present

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11
Q

What are Blaschko’s lines?

A

Developmental growth pattern of the skin
Thought to be along lines of cell migration during foetal development

Some skin conditions can develop along †hem

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12
Q

What are the 4 layers of the epidermis?

A

Keratin
Granular
Prickle cell
Basal

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13
Q

What type of tissue is epidermis made of?
How thick is it?
What cell type is it mostly made up of?
What other cells are present?

A

Stratified squamous epithelium
1.5mm thick
95% made of keratinocytes
Also contains:
Melanocytes, Langerhans cells, merkel cells

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14
Q

How is epidermal turnover regulated, and how is it lost?

A

Balance of cells in and out- via growth factors, cell death, and hormones

Loss of control with skin cancer and psoriasis

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15
Q

What is the process of differentiation?

A

When keratinocytes migrate from the basement membrane to the top- for continuous regeneration

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16
Q

keratin layer-

Latin name
Composition
Function

A

Stratum corneum

Made of corneocytes- dead keratinocytes that are still rich in keratin- provides structural strength). Source of house dust

Lipid matrix- surrounds corneocytes, crucial for skins waterproof barrier. Rich in filaggrin which contribute to strength and hydration

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17
Q

granular layer

Latin name
Contains..?
What happens to a cell at this stage

A

Stratum granulosum

Contains:
keratohyalin granules
filaggrin
involcurin proteins
Odland/lamellar bodies
^all contribute to strength and protective barrier

Cells lose nuclei at this stage

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18
Q

prickle cell layer

Latin name
Contains…?

A

Stratum spinosum

Contains many desmosomes for mechanical strength

and large polyhedral cells which synthesise keratin

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19
Q

basal layer

Latin name
Cell appearance
Contains..?

Significance to cancer

A

Stratum bassale

One cell thick, small cuboidal cells with many intermediate filaments (keratin)

Basal cell carcinoma is the most common skin cancer as this layer is very metabolically active (continuously produces more cells and melanin)

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20
Q

Melanin-
What are they produced by and where?
Where are they found
Types
Process of formation
Role

A

Produced by melanosomes in melanocytes (they migrate from neural crest up in first 3 months of foetal development)

Found in basal layer and above

2 types:
Eumelanin- brown/black in colour
Phaeomelanin- red/yellow in colour

Tyrosinase converts tyrosine to dopaquinone
Dopaquinone forms either type of melanin

Roles:
Photoprotection
Pigmentation
Antioxidant activity

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21
Q

langerhans cells-

What are they?
Where do they originate from?
Where are they found?
What do they do?

A

Type of dendritic cell that is an APC
Mesenchymal origin- bone marrow
Found mostly in prickle cell layer, but also dermis and lymph nodes

They pick up antigens in skin and circulate to lymph nodes, presenting them to T cells (initiating adaptive immune response)

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22
Q

merkel cells

Where are they found?
What do they do?

Possible complication

A

Found in basal layer between keratinocytes and nerve fibres

Essential for light and touch sensation

Rare but Merkel cell cancer is possible- very high mortality

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23
Q

How does white skin differ from darker skin?

A

Darker skin has more eumelanin, and keratin layer has more layers

In white skin melanosomes confined to basal layer but in darker skin they exist throughout

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24
Q

What is a key feature of mucosal membranes?
Give examples

A

Highly specialised for function-

Masticatory mucosa keratinised to deal with friction/pressure

Tongue mucosa specialised to deal with taste

Ocular mucosa- lacrimal and sebaceous glands, eye lashes

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25
Q

What is in between the epidermis and dermis?
What is its role?

A

The dermo-epidermal junction

Support and anchorage of epidermis
Semi permeable membrane acting as a barrier and a filter

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26
Q

What is the dermis made of?

A

Collagen (1 and 111) and elastin arranged in ground substance of hyaluronic acid and chondritin sulphate

27
Q

What is the main cell present in the dermis?

A

Fibroblast- collagen producing

28
Q

What other cells does the Dermis contain?

A

Macrophages
Mast cells
Lymphocytes
Langerhans cells

29
Q

What does the dermis contain?

A

Nerves
Muscles
Vasculature (inc lymphatics)

30
Q

What are the 2 layers of the dermis and how do they differ?

A

Papillary- thin, just below epidermis
Reticular- thick, bundles of type 1 collagen

Reticular contains appendage structures like sweat glands and pilosebaceous units

31
Q

Special feature of dermis circulation

A

Supply to skin exceeds metabolic need-

Arteriovenous anastomoses allow for superficial capillary bypass when cold to prevent heat loss

32
Q

Role of lymphatic system in skin

A

Sub epidermal network

Small non contractile vessels feed into large contractile trunks

Drains plasma proteins, extravasated cells and excess interstitial fluid

33
Q

Innervation of the skin

A

Autonomic-
Vessels nerves and glands

Somatic- sensory free nerve endings
Pressure detected by Pacinian corpuscle
Vibration detected by Meissners corpuscle

34
Q

Role of immune cells in the skin

A

mast cells- release histamine to cause itch
macrophages- phagocytic and APC- release cytokines

35
Q

What are the 3 types of skin gland?

A

Sebaceous
Eccrine
Apocrine

36
Q

What type of gland is a sebaceous gland?

A

Exocrine- secrets its products
Holocrine- product released by cell breakdown

37
Q

What are sebaceous glands commonly associated with?

A

Hair follicles

Acne

38
Q

Where are sebaceous glands found?

A

Mostly face and chest

39
Q

What are sebaceous glands sensitive to?

A

Hormones

Dormant pre puberty

40
Q

What do sebaceous glands produce?

What does the product do?

A

Produces sebum

Controls moisture loss and protects from fungal infection

41
Q

Where are eccrine sweat glands found?

A

Entire skin surface
Highest concentration on palms, soles, forehead, and axillae

42
Q

What do eccrine glands do?

A

Secrete sweat for thermoregulation (cooling), and moistening palms for grip
Under sympathetic cholinergic supply

NaCl and HCO3 is reabsorbed

43
Q

Where are apocrine glands found?

A

Associated with pilosebaceous units, concentrated in places where there is more hair eg groin, axilla, etc

44
Q

What do apocrine glands secrete?

A

An oily fluid, thicker than sweat and secreted in instances like arousal or stress

Can lead to odour after bacterial composition

45
Q

What makes up a pilosebaceous unit?

A

Hair follicle- bulb, isthmus, infundibulum
Hair shaft
Arrector pili muscle
Sebaceous gland

46
Q

Structure of Asian hair

A

Straight and round
Fast growth rate
Strong and durable

47
Q

Structure of Caucasian hair

A

Straight or curly
High density
High moisture content
High strength

48
Q

Structure of African hair

A

Curly
Low density
Slow growth rate
Fragile

49
Q

What are the 4 phases of hair growth?

A

Anagen- active growing (3-7 years)
Catagen- transitional (stopping growing)(3-4 weeks)
Telogen- growth fully stopped (3-4 months)
Exogen- shedding (every day)

50
Q

What hormones influence hair growth?

A

Thyroxine, androgens

51
Q

What are nails made of ?

A

Specialised keratins

52
Q

What is the nail growth rate?

A

0.1mm per day

53
Q

What do nails do?

A

Provide protection
Improve sensory feedback

54
Q

What is meant by 2 way barrier?

A

Prevents external harm (internal protection)
Prevents internal loss (outward regulation)

55
Q

How does the skin act as a barrier?

A

Physical protection- friction, mechanical trauma, UV
Chemical protection- irritants, allergens, toxins
Pathogenic protection- bacteria, viruses, fungi

56
Q

What is the role of vitamin D

A

Increase flow of calcium into blood (promotes absorption from food and reabsorption in kidneys)

57
Q

Vitamin D metabolism explained

A

UV-B (from sun) penetrates epidermis, and coverts 7-dehydrocholesterol to vitamin D3

58
Q

Significance of the skin to thyroid hormone metabolism

A

Only 20% of T4 is converted to T3 in the thyroid gland-

The rest occurs in peripheral tissues including the skin

59
Q

What is the skins role in thermoregulation?

A

Sweating to cool down
Blood flows through anastamoses to keep heat away from surface, to prevent heat loss
Pilorection- hairs stand up to trap air layer

60
Q

Skins role in immune defense

A

Langerhans and T cells

Protects against infection, sunlight responses, and allergic reactions

61
Q

Skins role in communication

A

Visual
Odour
Sociosexual behaviour

62
Q

Skins role in sensory function

A

Touch, pressure, vibration
Pain and itch
Hot and cold

63
Q

Requirements for skin function

A

Intact barrier
Functioning immune system
Functioning Vasculature
Means of regulation temperature
Normal sensory nerve function

Dermatology (16 decks)

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