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MSS & Skin > Skin: Structure & Function > Flashcards

Skin: Structure & Function Flashcards

1
Q

What is the integumentary system?

A

Refers to the skin, hair and nails.
Largest and heaviest organ of the body – ~15% of adult weight
Medically significant

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2
Q

What are the main functions of the skin?

A 
Barrier (protection), against:
- Dehydration
- Infection
- Injury / abrasion
- Solar radiation
Thermoregulation
Sensation
Repair
Vitamin D production
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3
Q

What is the Integumentary system composed of?

A 
3 layers of the skin 
Epidermis, Dermis, Hypodermis
Hairs
Glands
Sense organs
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4
Q

What is H&E stain?

A

Stained with H+E (Haematoxylin and eosin)

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5
Q

Describe the structure of hypodermis

A

Hypodermis can be the thickest layer - composed of fat

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6
Q

Describe the epidermis structure

A

Thinnest (in abdomen)

Thickest on the heel of your foot

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7
Q

What are the 4 layers of epidermis?

A

Basal layer - (Stratum basale)
Stratum spinosum - (spiny layer)
Stratum granulosum - (Granular layer)
Stratum corneum - (cornified layer)

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8
Q

Outline the features of the basal layer

A

(Stratum basale)
First single layer, containing stem cells, and attached to dermis.
Stem cells constantly proliferate

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9
Q

Why is the basal layer referred to as dynamic?

A

Daughter cells constantly move “up” (distally) through the epidermis, differentiating as they go, until they are shed from the outer surface
This takes ~20-50 days.

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10
Q

Describe the structure and function of the stratum spinosum

A

(spiny layer)
Cells have many desmosomes, (junctions) here visible as “spines” between the cells

Strong bonds holding the epidermis together

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11
Q

Describe the composition of the stratum granulosum layer

A

(Granular layer)
1-4 layers of cells containing prominent granules of “keratohyalin” (keratin precursor)

Also contain lamellar bodies containing lipids (seen by TEM)

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12
Q

Describe the function of the stratum granulosum cells

A

Cells are differentiating to form the outermost layer

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13
Q

What is the stratum corneum ?

A

(cornified layer)

The outer protective layer of the epidermis. Many cells thick.

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14
Q

Outline the composition of the stratum corneum

A

Squamous cells which have lost their nuclei,

Cornified – full of “horny” keratin (from keratohyalin granules) thus tough and resistant to injury

Nonpolar lipids (waterproof) are between the cells – from lamellar bodies

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15
Q

Name examples of other epidermal cell types and their roles

A 
Melanocytes  (pigment)
Langerhans cells  (defence)
Merkel cells  (sensation
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16
Q

What stain is used to view melanocytes?

A

Special (DOPA) stain for melanin shows their dendritic form

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17
Q

What is the role of melanocytes?

A

Melanocytes in the epidermis synthesise melanosomes (pigment granules)
and transfer them to basal keratinocytes through long dendrites

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18
Q

What is melanin?

A

Pigment mainly in basal epidermis

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19
Q

Where in the skin is melanin found?

A

Keratinocytes arrange melanin pigment in a cap distal to the nucleus (sunny side)
especially in basal layer (stem cells

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20
Q

Outline the role of melanin in UV protection

A

UV protection - black-skinned people have only about 10% as many skin cancers as white people with the same lifestyle

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21
Q

What are Merkel cells?

A

Oval shaped mechanoreceptors (pale) cells in the basal layer
Touch-sensors
Hard to tell difference with H&E alone in white people

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22
Q

What is the function of Langerhans cells?

A

Immune system. Antigen-presenting cells (like macrophages)

Also are dendritic cells, forming a network

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23
Q

Describe the appearance of Langerhans cells in H+E stain

A

Small, pale cells in non-basal layers of epidermis. Hard to see with H&E only

24
Q

Where is Vitamin D produced?

A

Vitamin D3, made in the epidermis. Mostly basal cells, also stratum spinosum

25
Q

Why is Vit. D deficiency more prevalent in darker skin tones?

A

Requires UV light.

Requires more UV light in dark skin (melanin barrier)

26
Q

Where in the body is Vitamin D converted to its active form?

A

Converted to active form in liver and kidney:
1,25 dihydroxyvitamin D3.
Commonly deficient in UK

27
Q

What is the dermis?

A

Dense, irregular connective tissue.
Dense = full of collagen fibres;
Irregular = fibres run in all directions (not parallel)

28
Q

What are the functions of the dermis?

A

Collagen provides tensile strength, (strength when pulled), hence protection against abrasion and impact

Contains elastin: protein complex providing elasticity

Dermis also carries blood and nerve supply for epidermis
Rich in blood vessels

29
Q

Describe the structure of the dermal-epidermal border

A

The dermal-epidermal border is often wavy, to resist shear forces (rubbing sideways). Especially on hands, = fingerprints, also feet

30
Q

What are rete ridges?

A

Epithelial extensions projecting into the underlying connective tissue in skin and mucous membranes

31
Q

Which layer of the skin contains rete ridges?

A

Epidermis can have rete ridges

Dermis can have finger-like dermal papillae (sing. = papilla)

32
Q

What is the hypodermis?

A

Aka fascia, or subcutis (Cutis = epidermis + dermis)

Where you put a hypodermic syringe, for a subcutaneous injection

33
Q

Describe the structure of the hypodermis

A

Composed of fat, containing glands, hair follicles, nerves, blood vessels.
Often the thickest layer of skin. Thickness varies with age, body site, nutrition etc

34
Q

What is the function of the hypodermis?

A

provides insulation, cushioning and energy storage

35
Q

Name the 3 types of glands present in the skin

A

Sebaceous glands
Apocrine sweat glands
Eccrine sweat glands

36
Q

What are Sebaceous glands?

A

Secrete oily sebum (“lanolin”) into hair follicle. Conditioner for hair and skin, prevents dryness and flaking

37
Q

What are the roles of the Eccrine sweat glands?

A

These are normal sweat glands. Watery secretion on to skin surface, cools the body by evaporation

38
Q

What is the function of the apocrine sweat glands?

A

Secrete into hair follicles
Oily fluid in humans, function unclear (contains pheromones in some mammals), but source of body odour after bacterial action
Found in armpits and anogenital region - Only after puberty
Less in Asian people

39
Q

What is the role of hair/follicles?

A

Hair: rudimentary in humans over much of body

Keeps the head warm but can be bald

40
Q

What infection is associated with hair follicles?

A

> also site of acne

Acne is when a follicle becomes blocked, and can get infected

41
Q

What is the nail matrix?

A

The equivalent to basal layer in rest of epidermis, where cells divide and forming nail

42
Q

What is the nail plate formed from?

A

Nail plate is made of keratin

Phalanx is the bone

43
Q

What is the role of thermoreceptors?

A

Heat / Cold sensors

44
Q

What do Meissner’s Corpuscle detect?

A

Senses touch

Merkel cells in basal epidermis also detect light touch

45
Q

What are nociceptor fibres?

A

Free nerve endings - sense pain

46
Q

What is the role of pacinian corpuscles?

A

Are baroreceptors that sense pressure

47
Q

Describe the structure of the skin at the fingertip

A

Paler structure in the middle of the fingertip is the neural structure in a dermal papilla

48
Q

How does the skin protect us against dehydration?

A

Epidermis: Keratin holds water, lipids stop it evaporating.

49
Q

What skin layer helps protect against infection?

A

Epidermis: Impervious barrier, also immune system

50
Q

Ho does the skin protect against injury?

A

All layers
Epidermis strong, rapid healing, thick where friction occurs.
Dermis has collagen – tough, leathery. Hypodermis cushions.

51
Q

What layer protects against solar radiation?

A

Epidermis – stratum corneum and melanin pigment

52
Q

How does the skin enable thermoregulation?

A

Hypodermis (insulation); thermoreceptors; blood supply regulation, sweating

53
Q

What allows sensation in the skin?

A

Nerve supply and various receptors

54
Q

How is skin repair enabled?

A

Epidermis – normal proliferation, and dermis – fibroblasts fill gaps with new collagen that epidermis can attach to

55
Q

What skin layer is responsible for Vit. D production?

A

Epidermis

56
Q

What structures innervate the skin?

A
  • Thermoreceptors
  • Meissner’s Corpuscle
  • Nocicpetors
  • Pacinian Corpuscle

MSS & Skin (6 decks)

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