Lecture 21: Skin Structure and Function Flashcards

1
Q

What are the 3 layers of skin?

A

Epidermis
Dermis
Hypodermis

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2
Q

What are the differences of the dermis in men and women?

A

Men - hypodermis thickest in abdomen and shoulders
Women - hypodermis thickest in hips, thighs, and buttocks

Both thick in palms of hands

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3
Q

What is the location of the hypodermis?

A

Lowest layer of skin

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4
Q

What are the 3 kinds of substances that hypodermis contain?

A

Mainly adipose tissue, neurovascular bundles, lymphatic

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5
Q

What kind of tissue is the hypodermis?

A

Loose connective tissue

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6
Q

What are the 5 functions of the hypodermis?

A
  1. Energy store
  2. Insulator
  3. Shock absorber
  4. Connects skin to underlying muscles and bones
  5. Makes hormones
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7
Q

What is the location of the dermis?

A

Between epidermis and hypodermis

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8
Q

What is corium?

A

Dermis

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9
Q

What is the cutis?

A

Dermis and epidermis

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10
Q

What are the 2 layers of dermis?

A

Papillary and reticular

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11
Q

What is the papillary?

A

Upper layer of dermis

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12
Q

What is the reticular?

A

Lower layer of dermis

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13
Q

What are the 3 functions of the dermis?

A
  1. Thermoregulation by hairs and sweat glands
  2. Sensory
  3. Gives structure to skin
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14
Q

What is the location of epidermis?

A

Outermost layer of epithelial cells (keratinocytes)

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15
Q

How many layers of cells is in the epidermis?

A

4-5

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16
Q

What are the cells held together laterally by?

A

Adherens junctions

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17
Q

What are the cells held together vertically by?

A

Desmosomes

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18
Q

What are the 6 functions of the epidermis?

A
  1. Prevent water loss
  2. Prevent entry to bacteria and parasites
  3. Special cells that present pathogens to immune cells
  4. Synthesis of keratin
  5. Prevents underlying tissue loss due to abrasion
  6. Allows gaseous exchange
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19
Q

What are the 5 layers of the epidermis?

A
  1. Stratum corneum
  2. Stratum lucidum
  3. Stratum granulosum
  4. Stratum spinosum
  5. Stratum basale
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20
Q

What is the stratum corneum?

A

Outermost corny or horny layer made of squamous dead keratinocytes

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21
Q

What is the stratum lucidum?

A

Transparent layer under stratum corneum only on palms and soles of feet

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22
Q

What is the stratum granulosum?

A

Granular layer

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23
Q

What kind of epithelial cells does the stratum granulosum have?

A

Stratified squamous epithelium

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24
Q

What are the 2 components of the stratum granulosum?

A

Lamellar granules (filament-associated proteins that assemble keratin fibrils and secrete it)

Tonofibrils (bundles of keratin filaments and keratohyalin granules)

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25
Q

What is the stratum spinosum?

A

Spinous layer

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26
Q

What kind of epithelial does the stratum spinosum have?

A

Cuboidal epithelium arranged in 3 layers held together by desmosomes

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27
Q

What is the function of stratum spinosum?

A

Produce lamellar bodies (keratohyalin factories)

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28
Q

What is the stratum basale?

A

Basal cell layer

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29
Q

What kind of epithelial cell does the stratum basale have?

A

Tall columnar epithelial cells

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30
Q

What are the 3 functions of stratum basale?

A

Renew keratinocytes by cell division
Keratinocytes make keratin filaments
Melanocytes produce melanin

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31
Q

What are keratinocytes?

A

Synthesize keratin that contribute to the strength of epidermis

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32
Q

What is the normal transit time of a keratinocytes from basal layer to stratum corneum?

A

28-40 days

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33
Q

What happens in psoriasis?

A

Transit time of keratinocytes from basal layer to stratum corneum reduced to 2-3 days, so stratum corneum is produced in abundance as silvery scales

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34
Q

What is hyperkeratosis?

A

Too much keratin put on the surface of skin especially on hands and feet

35
Q

What are mature melanosomes?

A

Contain melanin, transferred to neighboring keratinocytes by pigment, has dendritic processes that phagocytose things

36
Q

What is the function of melanocytes?

A

Produce melanin, not increased in number in dark or tanned skin

37
Q

What is melanin?

A

Main pigment that gives the skin its color

38
Q

What is the function of Langerhans cells?

A

Highly specialized capacity to present antigens to T lymphocytes to mediate immune reactions

39
Q

What are Merkel cells?

A

Mechanoreceptor cells associated with sensory nerve endings

40
Q

What is the function of Merkel cells?

A

Measure pressure and sensation

41
Q

What are the 5 steps of keratinocyte differentiation?

A
  1. Stratum basale: stem cells divide to replace superficial keratinocytes
  2. Stratum spinosum: keratinocytes bound by desmosomes, some continue to divide
  3. Stratum granulosum: keratinocytes stop dividing and produces large amounts of keratin and keratohyalin
  4. Stratum lucidum: thin layer of keratin
  5. Stratum corneum: keratinization (formation of layers of cells filled with keratin)
42
Q

What are the 4 ways to describe skin?

A

Hairy
Non hairy
Thin
Thick

43
Q

What are the 2 classifications of skin?

A

Hairy skin usually thin

Non hairy skin usually thick

44
Q

What are 3 exceptions to the hairy=thin and non hairy=thick skin?

A

Lips
Back of ear
Some areas of external genitalia

45
Q

What are 3 locations of non-hairy thick skin?

A

Palmar surface of hand
Plantar surface of foot
Webs between fingers and toes

46
Q

What are 3 characteristics of non hairy thick skin?

A

Thicker stratum corneum
Thinner dermis
Increase density of mechanoreceptors

47
Q

What are 3 functions of non hairy thick skin?

A
  1. Prevent tissue loss due to abrasion
  2. Increased friction between skin and surfaces
  3. Increased sensation
48
Q

What are 6 main differences between thick and thin skin?

A
  1. No hair follicles in thick, hair follicles in thin
  2. No sebaceous glands in thick, sebaceous glands in thin
  3. No arrector pili muscles in thick, arrector pili muscles in thin
  4. Pronounce ridges and furrows on surface in thick, smaller ridges and furrows in thin
  5. Regular shaped dermal papillae in thick, irregular dermal papillae in thin
  6. Stratum lucidum often seen in thick, stratum lucidum absent in thin
49
Q

What are skin appendages?

A

Skin associated structures that serve a particular function

50
Q

What are 5 examples of skin appendages?

A
Hairs 
Arrector pili 
Sebaceous glands
Sweat glands
Nails
51
Q

What are 3 types of hair?

A

Lanugo
Vellum
Terminal

52
Q

What is lanugo hair?

A

Covers developing fetus

53
Q

What is vellus hair?

A

Replaces lanugo at birth

54
Q

How does vellus hair look and feel like?

A

Short, thin, light colored and soft

55
Q

What is terminal hair?

A

Hair on head, axillae, external genital region

56
Q

How does terminal hair feel like?

A

Long, wide, dark colored and coarse

57
Q

What is terminal hair produced by?

A

Actions of testosterone

58
Q

What are the 4 functions of hair?

A

Thermoregulation
Sexual attraction
Sensation
Protection

59
Q

What are the 3 ways hair regulate temperature?

A

Hair lays flat when body temperature is normal or elevated
Hair stands erect when body temperature is lower than normal (arrector pili muscles contracts when stimulated by sympathetic fibres from ANS)
Partial barrier to UV rays

60
Q

What are the 2 ways hair cause sexual attraction?

A

Hairstyles can be alluring

Hairs trap pheromones secreted by apocrine sweat glands that attract the opposite sex and accentuate their pungency

61
Q

How does hair contribute to sensation?

A

Hairs have sensory nerve endings within the bulb so it can sense air movement, physical interactions and vibrations and transmit them to CNS, providing sensory awareness

62
Q

What are 4 ways hair protect the body?

A

Eyelashes and nasal hair prevents dust and pathogens from entering
Eyebrows reduce amount of light and sweat entering eye
Axilla hair acts to conduct sweat away from body
Oily hair aids escape when predation is imminent

63
Q

What is the structure of arrector pili muscle?

A

Smooth muscle fibres attached to papillary region of the dermis and hair bulb

64
Q

What are the 2 functions of arrector pili muscle?

A
  1. Contracts when cold or during flight of fight response

2. Induce sebum release from sebaceous gland

65
Q

What are the 7 locations of mechanoreceptors?

A
End bulbs
Free nerve endings
Tactile discs
Meissner corpuscle
Pacinian corpuscle
Ruffini’s corpuscle
Root hair plexus
66
Q

What does the end bulb sense?

A

It has thermoreceptors that sense temperature

67
Q

What do free nerve endings sense?

A

They have nociceptors that sense pain

68
Q

What are tactile discs?

A

Vertical dimpling of skin that attaches to basal layer keratinocyte

Meissen discs in hairy and Merkel discs in non hairy

69
Q

What do tactile discs sense?

A

Touch, pressure and texture

70
Q

What does the Meissner corpuscle sense?

A

Tapping and flicker movements

71
Q

What does the Pacinian corpuscle sense?

A

Vibration and pressure

72
Q

What does the Ruffini’s corpuscle sense?

A

Joint movements and tissue stretch

73
Q

What does the root hair plexus sense?

A

Vibrations in the hair shaft

74
Q

What is the location of nails?

A

Distal surfaces of phalanges

75
Q

What are nails solely consist of?

A

Alpha keratin

76
Q

What is the 4 components of a nail?

A

Nail plate, nail matrix, nail bed and grooves surrounding nail

77
Q

What are the 4 functions of nails?

A
  1. Protection of distal phalanx
  2. Enhance precise delicate movements through counter pressure exerted on pulp of finger
  3. Enhance sensitivity of fingertip
  4. Enabling extended precision grip
78
Q

What are the 10 functions of skin?

A
Protection
Repair
Thermoregulation 
Excretion of waste
Lubricator
Storage
Vitamin D synthesis
Absorption
Aesthetics
Sensation
79
Q

What are the 5 cells that protect and repair the skin?

A
  1. Keratinocytes - protect epidermis from abrasion
  2. Melanocytes - protect epidermis from UV
  3. Langerhans cells - protect epidermis from invasion
  4. Fibroblasts - wound healing
  5. Mast cells and macrophages - prevent infection
80
Q

Which structure in the skin regulates temperature and excretes waste products?

A

Sweat glands

81
Q

What waste products does the sweat glands excrete?

A

Urea, sodium chloride, water and CO2

82
Q

Which structure in the skin provides lubrication?

A

Sebaceous glands release oil onto surface

83
Q

Which structure in the skin stores energy?

A

Adipocytes

84
Q

What are 3 things the skin absorb?

A

Small amounts of water, O2 and drugs