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Histology > Skin > Flashcards

Skin Flashcards

1
Q

Cell types of the 2 skin layers?

A
  1. epidermis = epithelial layer of ectoderm origin

2. dermis = mesodermal connective tissue

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2
Q

What components strengthen adhesion b/w dermis/epidermis?

A
  • dermal papillae projections

- interdigitate w/ invaginating epidermal ridges

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3
Q

What is consistency of hypodermis?

A

Loose connective tissue w/ pads of adipocytes

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4
Q

Major cell types in epidermis? (4)

A
  1. keratinocytes (epithelium)
  2. melanocytes
  3. Langerhans cells (present antigens)
  4. Merkel cells (tactile epithelial)
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5
Q

4 layers of epidermis?

A
  1. basal layer (stratum basale)
  2. spinous layer (stratum spinosum)
  3. granular layer (stratum granulosum)
  4. stratum corneum
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6
Q

Describe basal layer

A
  • single layer of basophilic cuboidal/columnar cells
  • intense mitotic activity
  • contains progenitor cells (like stem cells) for all other layers
  • keratin production
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7
Q

Describe spinous layer

A
  • thickest layer
  • stratum germinativum is layer where some division still happening
  • tonofibrils are visible bundles near desmosomes
  • thicker in rough skin
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8
Q

Describe cells in spinous layer

A
  • polyhedral
  • central nuclei
  • nucleoli and cytoplasm actively synth keratins
  • short cytoplasmic projections
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9
Q

Describe granular layer

A
  • 3 to 5 layers of flattened cells
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10
Q

Describe cells in granular layer

A
  • cells keratinizing
  • cytoplasm filled w/ basophilic masses called keratohyaline granules
  • lamellar granules exocytosed from keratinocytes to produce lipid-rich layer around cells
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11
Q

What are keratohyaline granules?

A
  • dense, non-membrane-bound masses of filaggrin and proteins assoc w/ keratins of tonofibrils
  • lamellar granules w/ many lamellae and lipids
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12
Q

Describe stratum lucidum

A
  • found only in thick skin
  • thin, translucent layer of flattened eosinophilic keratinocytes
  • held together by desmosomes
  • no nuclei or organelles
  • cytoplasm only has packed keratin filaments
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13
Q

Describe stratum corneum

A
  • 15 to 20 layers of squamous, keratinized cells

- filled w/ birefringent filamentous keratins

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14
Q

What are squames?

A
  • fully keratinized or cornified cells
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15
Q

Cause of psoriasis

A
  • overactive T lymphocytes that trigger autoimmune rxn in skin
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16
Q

Mechanism of psoriasis

A
  • keratocytes produced & differentiate @ accelerated rates
  • thickening of epidermal layers
  • increased keratinization & desquamation
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17
Q

Symptoms of psoriasis

A
  • inflammation
  • redness
  • irritation
  • itching
  • scaling
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18
Q

What are eumelanins?

A
  • brown/black pigments produced by melanocytes
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19
Q

What pigment is found in red hair?

A
  • pheomelanin
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20
Q

LM features of melanocytes?

A
  • pale-staining, rounded cell bodies
  • attached by hemidesmosomes to basal lamina
  • long irregular cytoplasmic extensions that penetrate epidermis
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21
Q

EM features of melanocytes?

A
  • numerous small mitochondria
  • short cisternae of RER
  • well-dvp’d Golgi
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22
Q

Steps in melanin synth

A
  • tyrosinase converts Tyr into DOPA
  • DOPA transformed into melanin
  • melanin matures into melanosomes in vesicles
  • melanosomes transferred to nuclei of keatinocytes
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23
Q

Features & function of Langerhans cells

A
  • most clearly seen in spinous layer
  • present antigens to T lymphocytes
  • cytoplasmic processes extending from cells
  • dendritic
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24
Q

Features & function of Merkel cells

A
  • mechanoreceptors
  • light touch sensation
  • have neurosecretory granules w/ peptides
  • border basal lamina
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25
Q

Cause of bullous pemphigoid?

A
  • abnormalities of dermal-epidermal junction
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26
Q

Cause of bullous pemphigus?

A
  • autoimmune damage to intercell junctions b/w keratinocytes
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27
Q

Components of papillary layer of dermis

A
  • dermal papillae
  • loose connective tissue
  • types 1/3 collagen
  • anchoring fibrils of type 7 collagen into basal lamina
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28
Q

Components of reticular layer of dermis

A
  • thicker than papillary layer
  • dense irregular connective tissue
  • bundles of type 1 collagen
  • more fibers than papillary layer
  • dermatan sulfate
  • elastic fibers
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29
Q

Where does subpapillary plexus of capillary branches occur?

A
  • b/w papillary & reticular dermal layers
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30
Q

Where does deep plexus of blood/lymph vessels occur?

A
  • interface of dermis & subcutaneous layer
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31
Q

Describe Meissner corpuscles

A
  • ellipitical structures
  • consists of sensory axons winding among flattened Schwann cells perpendicular to epidermis in dermal papillae
  • initiate impulses when light touch against skin deforms their shape
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32
Q

Describe lamellated (pacinian) corpuscles

A
  • large oval structures
  • found deep in reticular dermis & hypodermis
  • concentric lamellae of flattened Schwann cells/collagen surr highly branched, unmyelinated axon
  • respond to course touch, pressure, vibrations
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33
Q

Describe Krause end bulbs

A
  • simple encapsulated, ovoid structures
  • extremely thin, collagenous capsules penetrated by a sensory fiber
  • sense low-freq vibrations in penis and clitoris
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34
Q

Describe Ruffini corpuscles

A
  • collagenous, fusiform capsules anchored to connective tissue
  • sensory axons
  • stim by stretch or twisting of skin
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35
Q

What sep’s hair follicle from dermis?

A

Glassy membrane (acellular hyaline layer)

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36
Q

Internal vs. external root sheath

A
  • internal surr initial part of hair root but degenerates above level of sebaceous glands
  • external covers internal, extends to epidermis
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37
Q

What muscles pulls hair shafts to erect position?

A

Arrector pili smooth mm

38
Q

3 major phases of hair growth cycle?

A
  1. Anagen = long pd of mitotic activity/growth
  2. Catagen = brief pd of arrested growth/regression of hair bulb
  3. Telogen = final long pd of inactivity
39
Q

What layer of epidermis is the cuticle an extension of?

A

Stratum corneum

40
Q

What layers of epidermis are included in the nail bed? (2)

A
  1. basal

2. spinous

41
Q

What category of gland is the sebaceous gland?

A

Acinar gland

42
Q

What is a pilosebaceous unit comprised of?

A
  • hair follicle

- sebaceous glands

43
Q

What are sebocytes?

A
  • flattened epithelial cells that produce lipids
  • filled w/ small fat droplets
  • assoc w/ acini of sebaceous glands
  • disintegrate near duct to release lipids (sebum)
44
Q

2 types of sweat glands?

A
  1. eccrine sweat glands

2. apocrine sweat glands

45
Q

3 cell types of secretory part of eccrine sweat glands?

A
  1. pale-staining clear cells on BL that produce sweat
  2. dark cells filled w/ eosinophilic granules that line lumen, merocrine secretions
  3. myoepithelial cells on BL, contract to move watery secretion into duct
46
Q

When/where are apocrine glands found?

A
  • after puberty

- skin of axillary & perineal regions

47
Q

Histo diff’s b/w apocrine and eccrine sweat glands?

A
  • eccrine: stratified cuboidal, pale-staining

- apocrine: larger lumens, simple cuboidal, eosinophilic, many secretory granules

48
Q

What type of secretion do apocrine glands do?

A

Merocrine (exocytosis of granules)

49
Q

Diff’s in innervations of apocrine/eccrine glands?

A
  • apocrine = adrenergic nerve endings

- eccrine = cholinergic nerve endings

50
Q

What are embryologic precursors to melanocytes?

A

Neural crest cells

51
Q

What are points of adhesion in melanocytes?

A
  • hemidesmosomes to BL

- no desmosomes

52
Q

Helpful feature to ID hypodermis?

A
  • presence of adipocytes
53
Q

What 3 sensations do Pacinian corpuscles register?

A
  1. coarse touch
  2. pressure from sustained touch
  3. vibration
54
Q

Defect in collagen-fibril processing would impact which layer the most?

A

Dermis (made of mostly collagen and elastic fibers)

55
Q

What cytoskeletal structure would be most prevalent on a melanocyte?

A

Hemidesmosomes

56
Q

What layer of skin would be the most likely origin of skin cancer?

A

Stratum basale

57
Q

What 2 molecules provide sealant b/w adjacent cells in epidermis?

A
  1. Lipids

2. Glycolipids

58
Q

Where are cells that produce pigment for dark hair located?

A

Hair matrix

59
Q

What separates hair follicles from the connective tissue of the dermis?

A

Glassy membrane

60
Q

What type of connective tissue is reticular dermis comprised of?

A

Dense irregular connective tissue

61
Q

What cells aid eccrine sweat glands in their secretory process?

A

Myoepithelial cells

62
Q

What cells share the same specific epidermal layer as Merkel cells?

A

Basal stem cells for keratinocytes

63
Q

T/F: vellus hair is present on most skin of the human body

A

True

64
Q

T/F: merocrine and apocrine sweat glands simple tubular coiled glands

A

True

65
Q

What are 2 special variants of loose connective tissue?

A
  1. adipose tissue

2. reticular connective tissue

66
Q

T/F: mucous connective tissue is common in adult ind’s

A

False

67
Q

How long does renewal of human epidermis thru mitotic activity take?

A

3-4 wks

68
Q

What color are basal cell carcinomas on slides and why?

A
  • big blue balls in the dermis

- b/c they are derived from basal cells, which appear blue on slides

69
Q

From which type of cell do basal and squamous cell carcinomas originate?

A

Keratinocytes

70
Q

Genes assoc w/ UV-related melanoma? (2)

A

BRAF and RAS

71
Q

Gene associated w/ familial melanoma?

A

CDKN2A

72
Q

Genes assoc w/ basal cell carcinoma? (2)

A

PTCH and SMO

73
Q

Gene assoc w/ squamous cell carcinoma?

A

p53

74
Q

Describe epidermodysplasia verruciformis (Treeman syndrome) (3)

A
  • increased susceptibility to HPV
  • high risk for skin cancer
  • growth of verrucae (warts) of hands and feet
75
Q

Genes assoc w/ EV syndrome and functions? (2)

A
  • EVER1 and EVER2

- supposed to regulate zinc, a cofactor for viral proteins that they limit access to by viruses

76
Q

Most common form of skin cancer?

A

Basal cell carcinoma

77
Q

Major diff in skin lesions from squamous vs basal cell carcinoma?

A
  • squamous = crusty appearance of papules

- basal = pearly appearance of papules

78
Q

ABCDE of melanoma?

A
  • Asymmetric pattern
  • Borders are irregular
  • Color is not uniform
  • Diameter>6mm
  • Evolution/growth over time
79
Q

Common melanoma in older pts w/ very slow growth rate?

A
  • Lentigo maligna melanoma

- good prognosis

80
Q

Most common melanoma in dark skinned pts?

A
  • Arcal lentiginous melanoma

- poor prognosis

81
Q

Precancerous condition that could lead to squamous cell carcinoma?

A

Actinic keratosis

82
Q

Gene defects implicated in epidermolysis bullosa simplex? (2)

A

Keratins 5 and 14

83
Q

Presentation of Epidermolysis bullosa simplex? (2)

A
  • blisters on hands/feet

- blisters are w/i basal layer

84
Q

What disease:

autoimmune blistering disease where keratinocytes can’t connect to one another?

A

Pemphigus vulgaris (spec attacks cells in stratum spinosum)

85
Q

Brief mechanism of Pemphigus vulgaris?

A

IgG autoantibodies against desmogleins (Dsg) 1 and 3

86
Q

Presentation of Pemphigus vulgaris? (3)

A
  • eroding skin
  • cornflake like appearance
  • ulcers
87
Q

What is Nikolsky’s sign? (2)

A
  • epidermis sep’s when you manually stroke skin

- sign of a serious blistering disease

88
Q

Histo presentation of PV? (3)

A
  • intra-epidermal cleft w/i stratum spinosum
  • acantholysis
  • net-like pattern under immunofluorescence of Ab’s
89
Q

Bullous pemphigoid is autoimmune disorder affecting what 2 genes and what protein?

A
  • BPAG1 or BPAG2

- hemidesmosomal proteins

90
Q

Histo effects of Bullous pemphigoid? (2)

A
  • split underneath basal cells

- linear immunofluorescence band @ DEJ

91
Q

Symptoms of Bullous pemphigoid?

A
  • fluid-filled blisters

- this shows blister is below epidermis

92
Q

What protein affected by Dystrophic epidermolysys bullosa?

A
  • inability to make Collagen 7 (anchoring collagen)

Histology (7 decks)

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