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Tissue biology > Lecture 4: The skin > Flashcards

Lecture 4: The skin Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Who described the skin as a protective covering 150 years ago?

A

Virchow

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2
Q

What is skin the largest of?

A

Largest organ in weight and surface area

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3
Q

What is the weight of the skin?

A

3-5kg in adult

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4
Q

What is the surface area of the skin?

A

1.5-2 meters squared in adults

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5
Q

Where is skin the thickest and where is it the thinnest?

A

Thickest: soles of feet
Thinnest: eyelids

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6
Q

What is skin rich in?

A

Antigen presenting cells (langerhans cells) for immune response uppon breach

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7
Q

What does skin facilitate the synthesis of?

A

Vitamin D3

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8
Q

What receptors does the skin contain?

A

Touch, pressure, pain and temperature

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9
Q

How does the skin provide protection from UV?

A

Pigmentation from melanin

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10
Q

How does the skin help thermoregulate?

A

Via blood circulation in extremities and sweat

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11
Q

What are the three main layers of the skin?

A

The epidermis, dermis and subcutis

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12
Q

What is the epidermis?

A

Continuously proliferating stratified squamous epithelium which provides a non-living layer of keratin

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13
Q

What is the dermis?

A

Consists of fibrous and fibroadipose tissue which supports the epidermis physically and metabolically

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14
Q

What does the subcutis consist of?

A

Adipose tissue and supporting fiborous bands

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15
Q

What are some of the specialised appendages found in the skin?

A

Nails, hair follicles, sebaceous glands, eccrine glands and apocrine glands

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16
Q

How is the epidermis adapted to withstand constant abrasion and deiccation?

A

Tough non-living surface layer composed of keratin wrapped in plasma membrane

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17
Q

The epidermis is _____, nourished by diffusion from the ____

A

Avascular

Dermis

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18
Q

What type of cell makes up 95% of the epidermis?

A

Keratinocytes

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19
Q

Other than keratinocytes, what 4 other cell types make up the epidermis?

A

Melanocytes
Langerhans cells
Merkel cells
Inflammatory cells

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20
Q

What is the area of tissue that joins the epidermis and the dermal layers called?

A

The dermoepidermal junction

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21
Q

What is the structure of the dermoepidermal junction?

A

Highly corrugated and has many downward, ridge like extensions of the epidermis called epidermal or rete ridges

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22
Q

Epidermal, or rete, ridges, project between alternating, upward projections of the dermis known as what?

A

Dermal papillae

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23
Q

What are the dermal papillae and rete ridges responsible for?

A

Exchange of nutrients

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24
Q

What would happen without rete ridges?

A

Skin would suffer premature ageing and damage

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25
Q

How many distinct layers are there to the epidermis?

A

4 or 5

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26
Q

What is the deepest layer of the epidermis called?

A

Basal layer/stratum basale

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27
Q

What is the structure of the basal layer?

A

Closely backed basophilic cuboidal to columnar epithelial cells (keratinocytes) resting on basemement membrane

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28
Q

What layer of the epidermis rests of the basal layer?

A

The prickle cell layer/ stratum spinosum

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29
Q

How thick is the prickle cell layer?

A

Several cells thick

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30
Q

What is the structure of the prickle cell layer?

A

Polyhedral cells become progressively flatter towards the surface

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31
Q

What is the second to the top layer of the epidermis?

A

Granular layer/ Stratum Granulosum

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32
Q

What is the structure of the granular layer?

A

3-5 layers of flattened cells, contains numerous basophilic granules (keratohyalin)

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33
Q

What is the keratin layer also called?

A

Stratum Corneum

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34
Q

What is the structure of the stratum corenum?

A

Dead, anucleate cells, keratin replaces cytoplasm

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35
Q

What is the stratum basale and spinosum sometimes collectively called?

A

Malpighian layer

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36
Q

What is the 5th layer of the epidermis?

A

Stratum lucidum

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37
Q

Where is the stratum lucidum found in the body?

A

Absent in thin skin, present in thick skin

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38
Q

What is the structure of the stratum lucidum?

A

A few layers of tightly packed squamous cells that lack organelles and nuclei

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39
Q

What colour is the stratum lucidum

A

Translucent

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40
Q

Where in the layers of the epidermis is the stratum lucidum found?

A

Transition from stratum granulosum to the corneum

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41
Q

What are mealanocytes?

A

Melanin pigment-producing cells that determine colour of skin and hair

42
Q

How are melanocytes linked?

A

Via dendritic processes (not desmosomes)

43
Q

What part of the cell produces melanin?

A

Membrane bound organelles known as melanosomes

44
Q

What form of melanin produces brown to black pigments?

A

Eumelanin

45
Q

What form of melanin produces yellow to red pigments?

A

Pheomelanin

46
Q

What do melanoma’s develop from?

A

Melanocytes in the skin and some in mucous membranes, uvea of the eye and meninges

47
Q

Malnocytes proliferate to form what?

A

Nevi

48
Q

What occurs subsequent to nevi formation?

A

Dyplasia, hyperplasia, invasion and metastasis

49
Q

What two things are used to detect melanoma cells?

A

Melan-A and human melanoma black (HMB)

50
Q

Where are Langerhans cells derived from and where are they found?

A

Monocyte-derived dendritic cells that reside in the epidermis

51
Q

What are Langerhans cells?

A

Phagocytic and antigen-processing and presenting cells

52
Q

What do Langerhans cells do once they have captured invading surface antigens?

A

Migrate to regional lymph nodes, induce immune response via antigen presentation to CD4+ and CD8+ T lymphocytes

53
Q

Where in the epidermis are Langerhans cells common?

A

Stratum spinosum and stratum granulosum

54
Q

What are merkel cells?

A

Intra-epidermal touch receptors

55
Q

What do Merkel cells contain in their cytoplasm?

A

Membrane bound vesicles

56
Q

What type of junction do merkel cells make with sensory nerves in the upper demis?

A

Synaptic junctions

57
Q

What are apocrine glands?

A

Limited distribution, possible function in producing odour

58
Q

What are eccrine glands?

A

Sweat glands- essential for thermoregulation

59
Q

What are sebaceous glands associated with?

A

Hair follicles

60
Q

What do sebaceous glands do?

A

Secrete sebum which may provide waterproofing

61
Q

Where is hair produced?

A

Follicles

62
Q

What shape are hair shafts and what are they composed of?

A

Cylindrical shafts composed of keratin

63
Q

What is the structure of a hair shaft?

A

Surface cuticle composed of a single layer of flattened keratin scales

64
Q

Other than sebaceous glands, hair is produces in association with what?

A

A smooth muscle bundle called arrector pilli

65
Q

What is the function of hair and fur in mammals?

A

Thermoregulation

66
Q

Hair growth is _____

A

cylindrical

67
Q

What are the three phases of hair growth?

A

Anagen, catagen, telogen

68
Q

What is anagen?

A

Long phase of active growth of hair

69
Q

What is catagen?

A

Short phage of involution

70
Q

What is telogen?

A

Short inactive involuted phase

71
Q

Where are sebaceous glands located?

A

Between hair follicles and its arrector pilli muscle

72
Q

What is sebum?

A

Lipid-rich decomposed cells

73
Q

Sebaceous glands empty their secretions via a ducts in the upper part of the hair follicle. This is known as?

A

Holocrine secretion

74
Q

Each sebaceous gland contains what layers?

A

A peripheral layer of cuboidal cells with spherical nuceli resting on a thin basement membrane

75
Q

The peripheral layers of cuboidal cells in the sebaceous gland give rise to what?

A

Larger, sebum-producing cells

76
Q

What is the structure of the sebum-producing cells?

A

Polyhedral with large amounts of lipid in the cytoplasm

77
Q

What happens to sebum producing cells nuclei?

A

They become pyknotic

78
Q

What gradually happens to sebum producing cells?

A

They gradually disintegrate into the secretory product

79
Q

What type of muscle to sebaceous glands have?

A

Smooth muscle (arrector pili)

80
Q

What does contraction of arrector pili in sebaceous glands do?

A

Compresses the gland to expel sebum

81
Q

What shape are eccrine (sweat) glands?

A

Simple, coiled tubular gland

82
Q

What to portions to eccrine (sweat) glands consist of?

A

Secretory and excretory duct portions

83
Q

The secretory part of the gland deep in the dermis consist of what?

A

Two types of cuboidal to pyramidal secretory cells: clear cells and dark cells

84
Q

What do clear cells in eccrine gland secrete?

A

Water and electrolytes

85
Q

What do dark cells in eccrine glands secrete?

A

Macromolecules

86
Q

What cells border secretory cells in the ecrrine gland?

A

Myoepithelial cells (smaller, intensely eoisinophilic)

87
Q

What do myoepithelial cells do?

A

Mainly contractile and help expel sweat into the lumen

88
Q

What two layers make up the excretory duct of the eccrine gland?

A

Dark staining cuboidal epithelial cells

89
Q

What does the excretory duct of the eccrine gland lack?

A

Myoepithelial cells

90
Q

Where in the body are apocrine glands found?

A

Mainly in the axilla and groin

91
Q

Where is the secretory compartment of the aporcine gland located?

A

In deep reticular dermis or subcutis

92
Q

How is the secretion of the apocrine gland carried to the upper part of the hair folicle?

A

A duct system

93
Q

What shape is the secretory gland of the apocrine gland?

A

A coiled tubular type with a widely dilated lumen

94
Q

What shape are the apocrine glands secretory cells?

A

Low cuboidal, eosinophilic cytoplasm

95
Q

What is between the secretory cells and the basement membrane of the apocrine gland?

A

A discontinous layer of myoepthilial cells

96
Q

What is the dermis composed of?

A

Bundles of collagen fibres and strands of elastic fibres embedded in acellular ground substance

97
Q

What do fibroblasts in the dermis do?

A

Synthesise collagen, elastic fibres and the matrix

98
Q

What are the two layers of the dermis?

A

Superficial papillary dermis

Deeper reticular dermis

99
Q

What is the papillary dermis?

A

Loose, contains fine interlacing collagen (red) and elastic fibres (black)

100
Q

What else does the papillary dermis contain?

A

Arterioles, capillary loops and venules as well as lymphatics

101
Q

What is the reticular dermis?

A

Generally a thicker layer, interface may be poorly defined

Tissue biology (7 decks)

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