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microanatomy > skin > Flashcards

skin Flashcards

1
Q

What are the two main types of skin thickness and where are they found on the body?

A

Thick skin is found on the palms and soles.

Thin skin covers the majority of the body.

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2
Q

What is the range of skin thickness on the body?

A

less than 1mm to over 5mm.

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3
Q

Name the main layers of the skin.

A

epidermis, dermis, and hypodermis (subcutaneous fat).

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4
Q

True or False: The hypodermis is part of the skin.

A

False. The hypodermis is closely associated with the skin but is not considered part of it.

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5
Q

How many layers are in the dermis, and what is its primary function?

A

2 layers and provides strength and elasticity to the skin through collagen and elastin fibers.

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6
Q

How many layers are in the epidermis, and what is its role?

A

5 layers and serves as the outermost protective barrier.

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7
Q

What type of skin covers areas such as the palms and soles, and how does it differ histologically from other skin?

A

Thick skin covers the palms and soles and has a thicker epidermis with a prominent stratum lucidum layer, which is absent in thin skin.

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8
Q

What type of epithelium is the epidermis composed of?

A

Stratified squamous epithelium

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9
Q

Which cells populate and regenerate the epidermis?

A

Keratinocytes

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10
Q

How many layers (strata) are in the epidermis, and what are their names?

A

5 layers (strata):

Stratum Corneum

Stratum Lucidum (only in thick skin)

Stratum Granulosum

Stratum Spinosum

Stratum Basale

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11
Q

Which epidermal layer is found only in thick skin, such as on the palms and soles?

A

Stratum Lucidum

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12
Q

What is the approximate time it takes for the epidermal cells to renew from basal to superficial layers?

A

15-30 days

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13
Q

What structures are produced by invaginations of the epidermis?

A

Sweat glands and hair follicles

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14
Q

What are epidermal pegs (or ridges), and what is their role?

A

Epidermal pegs are extensions of the epidermis that interlock with the dermis, helping to anchor the two layers together.

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15
Q

Does the epidermis contain blood vessels?

A

No, its avascular; it receives nutrients from the underlying dermis.

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16
Q

What sensory structures are found in the epidermis?

A

Free nerve endings (sensory receptors)

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17
Q

What process do keratinocytes undergo in the Stratum Corneum?

A

Cornification – where keratinocytes become flattened, dead cells called squames.

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18
Q

What happens to the nuclei and organelles of keratinocytes in the Stratum Corneum?

A

They are lost; keratin filaments replace the cytoplasm in these cells.

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19
Q

How thick is the Stratum Corneum in thick skin?

A

It has 15-20 layers of squamous cells in thick skin.

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20
Q

What is desquamation in the context of the Stratum Corneum

A

shedding of surface cells, which are continuously replaced to maintain the thickness of the Stratum Corneum.

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21
Q

What is the function of the extracellular lipid layer in the Stratum Corneum?

A

It creates a water barrier to prevent water loss from the skin.

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22
Q

Where is the Stratum Lucidum found in the body?

A

It is found only in thick skin, such as on the palms and soles, and is absent in thin skin.

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23
Q

Describe the appearance and structure of the Stratum Lucidum.

A

It is a thin, transparent layer of flattened keratinocytes with a refractile appearance that stains poorly.

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24
Q

Do keratinocytes in the Stratum Lucidum contain nuclei or organelles?

A

No, the nuclei and organelles are degenerated and absent.

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25
Q

How is the Stratum Lucidum related to the Stratum Corneum?

A

It is considered a subdivision of the Stratum Corneum.

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26
Q

How thick is the Stratum Granulosum in thin vs. thick skin?

A

In thin skin, it is a thin or interrupted layer, while in thick skin, it is about 3-4 cell layers thick.

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27
Q

What process do cells undergo in the Stratum Granulosum?

A

Cells undergo keratinization, where they fill with keratin as they move toward the surface to eventually be sloughed off.

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28
Q

What are keratohyalin granules, and what is their function in the Stratum Granulosum?

A

Keratohyalin granules are basophilic granules that accumulate in cells, helping adhere keratin filaments together and initiate the cornification process.

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29
Q

Are nuclei and organelles present in the cells of the Stratum Granulosum?

A

Yes, nuclei and organelles are present initially, but cells soon degenerate and flatten as they prepare to move to the surface.

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30
Q

Which layer is typically the thickest in the epidermis?

A

The Stratum Spinosum is usually the thickest layer of the epidermis.

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31
Q

How are keratinocytes connected in the Stratum Spinosum, and what appearance does this give?

A

connected by desmosomes (junctional complexes), giving them a spiny or prickly appearance.

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32
Q

What activity do keratinocytes in the Stratum Spinosum exhibit?

A

mitotic activity (cell division) and actively synthesize keratins.

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33
Q

Describe the appearance of nuclei in the Stratum Spinosum.

A

Cells have round, euchromatic nuclei, indicating active gene transcription.

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34
Q

Where is the Stratum Basale located?

A

It is the deepest layer of the epidermis, adjacent to the dermis.

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35
Q

What is the structure of cells in the Stratum Basale?

A

It consists of a single layer of cuboidal or columnar cells.

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36
Q

What role do the cells in the Stratum Basale play in the epidermis?

A

The Stratum Basale contains progenitor cells that give rise to new keratinocytes through active mitotic division, pushing them upward through the layers of the epidermis.

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37
Q

What kind of nuclei do cells in the Stratum Basale have?

A

Cells in this layer have round, euchromatic nuclei, indicating active gene transcription.

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38
Q

What structure does the Stratum Basale rest on?

A

It rests on the basal lamina of the basement membrane.

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39
Q

What other important cell type is found in the Stratum Basale?

A

Melanocytes are present in this layer, responsible for producing melanin.

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40
Q

Where is thick skin found on the body?

A

Thick skin is found on the palms of the hands and the soles of the feet.

41
Q

What is the function of thick skin, and why is it important?

A

subject to most abrasion and provides protection in areas that experience high friction.

42
Q

How thick is the epidermis in thick skin?

A

ranges from 0.8 mm to 1.5 mm thick.

43
Q

Does thick skin contain hair or sebaceous glands?

A

No, thick skin is hairless and does not contain sebaceous glands.

44
Q

What glands are present in thick skin?

A

Sweat glands are present in thick skin.

45
Q

Where is thin skin found on the body?

A

covers the majority of the body.

46
Q

How thick is the epidermis in thin skin?

A

ranges from 0.5 mm on the eyelid to 5 mm on the back.

47
Q

What is the characteristic of the hair follicles in thin skin?

A

its hairy and contains hair follicles.

48
Q

What types of glands are present in thin skin?

A

contains sebaceous glands (associated with hair follicles) and sweat glands.

49
Q

How does the thickness of the dermis in thin skin compare to thick skin?

A

can vary in thickness depending on the area of the body.

50
Q

Corneum

A

thick > thin

51
Q

Granulosum

A

thick > thin

51
Q

Lucidum

A

Absent in thin, only thick

52
Q

Spinosum

A

thick > thin

53
Q

Basale

A

thick = thin

54
Q

What are keratinocytes, and what is their role in the epidermis?

A

highly specialized epithelial cells that make up the majority of the epidermis and are responsible for producing keratin, a protein that provides structure and protection.

55
Q

What is the function of Langerhans cells in the epidermis?

A

antigen-presenting cells involved in signaling in the immune system, helping to detect and respond to pathogens.

56
Q

What do melanocytes produce, and what is their function?

A

pigment-producing cells that produce melanin, the pigment responsible for skin color and protection against UV radiation.

57
Q

What role do Merkel cells play in the epidermis?

A

mechanoreceptor cells that are associated with sensory nerve endings, helping detect light touch and pressure.

58
Q

What percentage of the cells in the epidermis are keratinocytes?

A

85% of the cells in the epidermis are keratinocytes.

59
Q

Where do keratinocytes originate in the epidermis

A

originate in the Stratum Basale.

60
Q

What do keratinocytes produce, and what is its function?

A

produce keratins, the major structural protein of the epidermis, providing strength and protection to the skin.

61
Q

What role do keratinocytes play in the formation of the skin’s protective barrier?

A

participate in the formation of the epidermal water barrier, preventing water loss from the body.

62
Q

What happens to the keratinocytes as they mature and move toward the surface of the skin?

A

undergo terminal differentiation, and the exfoliated cells are constantly replaced by new ones from the Stratum Basale.

63
Q

What type of cells are Langerhans cells, and what is their primary function?

A

immune cells, specifically antigen-presenting cells (APCs), which help in immune surveillance by identifying pathogens and foreign substances.

63
Q

Where do Langerhans cells originate and how do they reach the epidermis?

A

originate in the bone marrow and migrate to the epidermis via the bloodstream.

64
Q

What percentage of the cells in the epidermis are Langerhans cells?

A

2%-5% of the cells in the epidermis

65
Q

In which layer of the epidermis are Langerhans cells commonly found?

A

commonly found in the Stratum Spinosum layer.

66
Q

How do Langerhans cells monitor the outer environment?

A

provide immunosurveillance of the epidermis by “sensing” the outer environment through their dendritic processes.

66
Q

How do Langerhans cells appear under routine histological stains?

A

Langerhans cells stain very poorly with routine histological stains.

67
Q

Where are melanocytes predominantly located in the epidermis?

A

predominantly located in the Stratum Basale of the epidermis.

68
Q

What do melanocytes synthesize, and how do they contribute to skin color?

A

synthesize melanin granules, which are transferred to keratinocytes, contributing to skin color.

69
Q

What is the shape of melanocytes and their processes?

A

“octopus-like” processes that extend between keratinocytes to transfer melanin.

70
Q

How do melanocytes appear in H&E-stained sections?

A

appear clear in H&E-stained sections due to their lack of affinity for the stain.

71
Q

Does the number of melanocytes vary significantly among different races?

A

approximately the same across different races, though the amount of melanin produced varies.

72
Q

What is the structure of the epidermal-dermal junction?

A

scalloped margin, consisting of epidermal pegs and dermal papillae.

73
Q

What is the function of the epidermal-dermal junction?

A

strengthens the attachment of the epidermis to the underlying dermis.

74
Q

Where is the dermis located in relation to the epidermis and hypodermis?

A

The dermis is situated deep to the epidermis and overlies the hypodermis.

75
Q

What are the two layers of the dermis?

A

Papillary layer – Loose connective tissue

Reticular layer – Dense irregular connective tissue

76
Q

What key structures and components are found in the dermis?

A

Collagen and elastic fibers (providing strength and stretch)

Blood & lymphatic vessels (for temperature regulation and blood pressure)

Nerves/nerve endings and encapsulated receptors

Hair follicles, sebaceous glands, and sweat glands

77
Q

What type of connective tissue makes up the papillary layer?

A

composed of loose connective tissue.

78
Q

What are the dermal papillae, and where are they located?

A

small, finger-like projections found in the papillary layer that interlock with the epidermis.

79
Q

What structures are contained within the papillary layer?

A

Loops of small blood vessels (capillaries)

Nerve endings (including sensory receptors)

80
Q

What type of connective tissue makes up the reticular layer?

A

composed of dense irregular connective tissue.

81
Q

What is the role of the reticular layer in the dermis?

A

forms the bulk of the dermis, providing strength and structure to the skin.

82
Q

What is another name for the hypodermis?

A

superficial fascia or subcutaneous tissue.

83
Q

What structures are found in the reticular layer?

A

Blood vessels

Lymphatic vessels

Nerves/nerve endings

84
Q

Where is the hypodermis located, and is it considered part of the skin?

A

located deep to the dermis, but it is NOT part of the skin.

84
Q

What type of connective tissue is the hypodermis composed of?

A

composed of loose connective tissue with adipose tissue.

84
Q

What are the functions of the hypodermis?

A

A major energy storage site

Insulation to maintain body temperature

Cushioning to protect underlying tissues

85
Q

What structures are found in the hypodermis?

A

Hair follicles with sebaceous glands

Smooth muscle cells (arrector pili, causing goosebumps)

Sweat glands

Encapsulated sensory receptors

86
Q

Hair Follicles

A

Thin skin ONLY with sebaceous glands Similar development to teeth

86
Q

Sebaceous Glands

A

Simple, branched acinar glands sebum (lipid-rich/oily secretion)

87
Q

Do sweat glands occur in both thick and thin skin?

A

Yes, associated with both thick and thin skin.

88
Q

Where are sweat glands located in relation to the skin layers?

A

secretory portion is located deep in the dermis or hypodermis, and the duct continues to the surface of the skin.

88
Q

What type of glands are sweat glands, and what is their shape?

A

simple coiled tubular glands

88
Q

Apocrine

A

secretes thick, odorous fluid into hair follicles

89
Q

Eccrine

A

discharges watery fluid onto skin surface

90
Q

Where are tactile receptors located in the skin?

A

either superficial or deep in the dermis (or hypodermis).

91
Q

What stimuli do tactile receptors respond to

A

respond to touch, pressure, and vibration.

microanatomy (9 decks)

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