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BMS08 > Histology Of Skin & Its Appendages > Flashcards

Histology Of Skin & Its Appendages Flashcards

1
Q

What is the largest organ of the body?

A

Skin

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2
Q

How much of your body weight is skin?

A

16%

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3
Q

What are the two layers of skin?

A

Epidermis (epithelial)

Dermis (connective tissue)

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4
Q

What are the dermal papillae?

A

Where dermis rises into epidermis

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5
Q

What are epidermal ridges?

A

Where epidermis dips into dermis

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6
Q

Why is the dermal/epidermal junction not flat?

A

Aids adhesion

Layers do not slip and slide easily

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7
Q

What are the functions of the epidermis? (2)

A

Protection (mechanical, chemical, thermal; infection; UV radiation)

Prevent desiccation (waterproof cornified layer)

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8
Q

What are the functions of the dermis? (2)

A

Sensation (touch, heat, pressure)

Thermoregulation (blood flow, sweat, insulation) - with hypodermis

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9
Q

What are the two classifications of skin?

A

Thick

Thin

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10
Q

What is the main difference between thick and thin skin?

A

Thick has no hair follicles

Thin has hair follicles generally

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11
Q

What kind of hair is found on the body skin?

A

Vellus hair - sparse, fine

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12
Q

What kind of hair is found on the scalp?

A

Terminal hair - numerous, closely-packed, coarse

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13
Q

Describe the cell arrangement of the thickest layer of the epidermis

A

Stratified squamous keratinising epithelium

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14
Q

What is the main cell type in the epidermis?

A

Keratinocyte

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15
Q

What is the scientific name for the basal layer?

A

Stratum basale

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16
Q

What shape are the cells in the basal layer?

A

Cuboidal or columnar

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17
Q

What occurs in the basal layer?

A

Cell division

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18
Q

What is the scientific name for the prickle cell layer?

A

Stratum spinosum

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19
Q

Why is it called the prickle cell layer?

A

During slide preparation, the cells are pulled apart but spot desmosomes remain intact

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20
Q

What occurs in the prickle cell layer?

A

Cells enlarge and accumulate large quantities of keratin

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21
Q

How is keratin organised in the prickle cell layer?

A

Organised into filaments and form bundles that converge on desmosomes

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22
Q

What is Pemphigus?

A

Blistering disease due to autoantibodies attacking desmoglein-3

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23
Q

What is the scientific name for the granular layer?

A

Stratum granulosum

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24
Q

What occurs in the granular layer?

A

Cells begin to flatten

Keratohyaline granules appear

Cells synthesise profilaggrin

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25
Q

What does filaggrin do?

A

Aggregates keratin filaments:

Facilitates cell flattening

Contributes to barrier function

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26
Q

What do filaggrin mutations cause?

A

Ichthyosis vulgaris

Increased risk of eczema, allergic rhinitis, peanut allergy

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27
Q

What is the scientific name of the cornified layer?

A

Stratum corneum

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28
Q

What occurs in the cornified layer?

A

Cells become squamous as keratins become cross-linked by disulfide bridges

Cells die, lose organelles and become dehydrated

Involucres becomes cross-linked —> cornified envelope

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29
Q

Give the name of a membrane-coating granule (/3)

A

Odland bodies

Lamellar bodies

Keratinosomes

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30
Q

What do membrane-coating granules do?

A

Fuse together in inter membrane space

Form multiple lipid bilayers arranged in sheets

Water-tight/permeability barrier

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31
Q

How long does it take for a cell to move from the basal layer to the surface of the skin?

A

25-50 days

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32
Q

What do melanocytes produce?

A

Melanin

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33
Q

What is melanin for?

A

UV protection

34
Q

In what organelle is melanin stored?

A

Melanosomes

35
Q

Explain the appearance of melanocytes in H&E staining

A

Clear with dark nucleus

Melanosomes are lipid-soluble

So are removed in slide preparation

36
Q

Where are melanocytes found?

A

Basal layer

Every 5-10 keratinocytes

37
Q

What gives rise to different races/skin colours?

A

Activity of melanocytes

NOT quantity

38
Q

Why do epidermal cells arrange melanin as a cap?

A

Cap over nucleus

Protects DNA from UV damage/radiation

39
Q

What causes vitiligo?

A

Autoantibodies destroy melanocytes

40
Q

What is vitiligo?

A

Random areas of skin lose pigment

41
Q

What cells other than keratinocytes and melanocytes are present in the skin?

A

Langerhans cells

Merkel cells

42
Q

Where are Langerhans cells found?

A

Upper prickle layer/beneath granular layer

43
Q

What is the function Langerhans cells?

A

Immunological defence (process foreign antigen, macrophage-like)

44
Q

How do we stain for Merkel cells?

A

Antibodies

45
Q

Where are Merkel cells found?

A

Basal part of epidermis

46
Q

What may be the function of Merkel cells and what suggests this?

A

Sense perception

Sensory nerve processes terminate on these cells

47
Q

What kind of connective tissue is the dermis?

A

Dense irregular connective tissue

48
Q

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

A

Thinner papillary layer - denser collagen

Less dense reticular layer - thicker collagen bundles

49
Q

What are the imaginary lines that collagen in the dermis follow?

A

Langer’s lines/lines of cleavage

50
Q

What and where are the two plexuses of the dermis?

A

Subpapillary - superficial

Cutaneous - deep

51
Q

What structures aid thermoregulation in the circulation of the dermis?

A

Arteriovenous shunts

52
Q

What are the two types of corpuscles in the dermis? Where are they in the dermis?

A

Meissner’s - superficial, sit in dermal papillae

Pacinian - deep

53
Q

What do Meissner’s corpuscles detect?

A

Light touch, pain, heat

54
Q

What do Pacinian corpuscles detect?

A

Pressure

55
Q

Where are the greatest and smallest densities of Pacinian corpuscles in the body?

A

Greatest in fingertips

Smallest in back

56
Q

What do free nerve endings sense?

A

Touch, pain, temperature

57
Q

What type of connective tissue is the hypodermis?

A

Loose

58
Q

What cell is abundant in the hypodermis and allows mobility of skin?

A

Fat/adipose cells

59
Q

What anchors the dermis to the deep fascia?

A

Fibrous bands/collagen bundles traversing downwards through hypodermis

60
Q

What type of gland is a sweat gland?

A

Exocrine

61
Q

What kind of secretion do the majority of sweat glands carry out?

A

Merocrine (eccrine glands)

62
Q

What is the typical shape of a sweat gland?

A

Unbranched, coiled, tubular

63
Q

What part of the nervous system innervates sweat glands?

A

Sympathetic

64
Q

What does the secretory region of an apocrine sweat gland look like under a microscope?

A

Single layer of cuboidal cells with a layer of myoepithelial cells

Large lumen

65
Q

What does the excretory duct of an eccrine sweat gland look like under a microscope?

A

Double layer of cuboidal cells

66
Q

Where are apocrine sweat glands found and when do they develop?

A

Axilla and genital regions

From puberty

67
Q

What do apocrine sweat glands discharge into?

A

Hair follicles

68
Q

What kind of sweat is produced by apocrine sweat glands?

A

Sticky, milky, odourless

69
Q

What kind of sweat is produced by normal sweat glands?

A

Hypotonic (after reabsorption of NaCl)

70
Q

What causes apocrine sweat to smell?

A

Microorganism attack

71
Q

What do sebaceous glands secrete?

A

Sebum

72
Q

What kind of secretion do sebaceous glands carry out?

A

Holocrine

73
Q

What do sebaceous glands discharge into?

A

Middle portion of hair follicles

74
Q

What are arrector pili muscles?

A

Bundle of smooth muscle attached to base of hair follicle (connective tissue sheath)

75
Q

What are the 6 concentric layers in a hair follicle?

A

Medulla (thick hairs only, lightly keratinised)

Cortex (heavily keratinised, polygonal cells)

Cuticle (very heavily keratinised scales)

Inner root sheath

Outer root sheath (contains stem cells, continuous with epidermis)

Glassy membrane

76
Q

What is the role of the hair papilla?

A

Direct hair formation

77
Q

How could you describe hair growth?

A

Intermittent

78
Q

What is the term for when a hair follicle that has stopped growing for a period?

A

Quiescence

79
Q

What are the lengths of the growth and rest periods of scalp hair?

A

Growth = years

Rest = 3 months

80
Q

What are the lengths of the growth and rest periods of body hair?

A

Growth = months

Rest = years

81
Q

What does the secretory region of an eccrine sweat gland look like under a microscope?

A

Stratified cuboidal cells surrounded by a layer of myoepithelial cells

Small lumen

BMS08 (7 decks)

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