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HUBS192 > Skin > Flashcards

Skin Flashcards

1
Q

What is the primary function of the skin?

A

Protection

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2
Q

Name the 3 layers of the skin

A

Epidermis, dermis and hypodermis

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3
Q

What 2 layers of the skin forms the cutaneous?

A

demis and epidermis

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4
Q

Which layer of the skin is most vascular?

A

the dermis

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5
Q

What are papules?

A

The wavy surface of the epidermis that creates increased surface area to maximise nutrient supply

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6
Q

What tissue type primarily makes up the epidermis?

A

Epithelial tissue

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7
Q

What is the difference between simple and stratified epithelia?

A 
Simple = 1 layer of cells
Stratified = stacked layers of cells
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8
Q

Describe the shape of squamous cells

A

flat, long, squashed etc.

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9
Q

Describe the shape of cuboidal cells

A

cube shaped, similar l and w proportions

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10
Q

Describe the shape of columnar cells

A

long, tall, columns, pillars

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11
Q

Name 3 types of epithelia

A

Squamous, cuboidal, columnar

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12
Q

Name the 5 layers of the epidermis in thick skin (in order from outside in)

A
  1. Stratum corneum
  2. Stratum lucidum (this is the bonus layer, not found in thin skin)
  3. Stratum granulosum
  4. Stratum spinosum
  5. Stratum basale
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13
Q

Describe cells in the stratum corneum

A

dead, dried out, no nuclei

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14
Q

Describe cells in the stratum lucidum

A

Transparent, only found in thick skin

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15
Q

Where is thick skin found in the body?

A

palms of hands and soles of feet

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16
Q

Describe cells in the stratum granulosum

A

contain granules that promote dehydration of the cell/cross linking of collagen fibres, secrete waxy material into intercellular space

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17
Q

Describe cells in the stratum spinosum

A

Linked by desmosomes (within this layer), get flatter as they go up

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18
Q

Describe cells in the stratum basale

A

columnar/tall regenerative cells, can divide, daughter cells migrate upwards to replenish layers above

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19
Q

How is the dermis anchored?

A

By hemidesmosomes, from the stratum basale of epidermis to the dermis

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20
Q

Name the 2 layers of the dermis

A

papillary and reticular layers

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21
Q

Describe the papillary layer of the dermis

A

Highly vascularised tissues for nourishment for dermis and epidermis

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22
Q

Describe the reticular layer of the dermis

A

‘Mesh-like’ structure of collagen and elastin fibres (for strength)

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23
Q

Name the plexuses of the dermis

A

cutaneous and subpapillary

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24
Q

What is a plexus?

A

A network (of blood vessels or nerves)

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25
Q

Where is the cutaneous plexus found?

A

at junction of dermis/hypodermis, in the reticular layer of the dermis

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26
Q

Where does the cutaneous plexus supply?

A

Supplies blood to hypodermis, lower dermis incl. capillaries for hair follicles and sweat glands
= nourishment

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27
Q

Where is the Subpapillary Plexus found?

A

Branches from the cutaneous plexus, deep to the papillary layer

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28
Q

Where does the subpapillary plexus supply?

A

Network of blood vessels providing O2 and nutrients to the upper dermis and epidermis

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29
Q

What cells dominate the hypodermis? What do they produce?

A

adipocytes that produce subcutaneous fat

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30
Q

Describe a 1st degree burn

A
  • Superficial, only outer layer of epidermis
  • Red/pink, dry, painful
  • No blisters
  • Skin retains water and antibacterial properties
  • Heals in 3-10 days
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31
Q

Describe a 2nd degree burn

A
  • Epidermis + varying amounts of dermis
  • Painful, moist, red and blistered.
  • Usually heal in approx. 1-2 weeks (needs good dressings)
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32
Q

What happens if a 2nd degree burn is deeper/more serious

A

○ White waxy layer secreted by stratum granulosum may be exposed
○ Hair follicles, sweat glands still intact
○ Heals in 1 month
○ May have loss of some sensation, scars

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33
Q

Describe a 3rd degree burn

A
  • aka full thickness burns (because extend into subcutaneous and may involve muscle/bone)
  • Colour: waxy white to red/black
  • Skin = hard, leathery
  • No pain in these areas because nerve endings destroyed
  • May require skin grafting
  • Weeks-years to regenerate, scarring
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34
Q

What is hair made of and where is it produced?

A

hard, dead, keratinised cells produced inside a hair follicle

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35
Q

What is the function of the erector pili muscle?

A

contraction pulls hair shaft upright = goose bumps, forms sealed pocket of air that traps body heat, helps with insulation

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36
Q

What is the root hair plexus?

A

A network of sensory nerves at base of each hair follicle resulting in heightened sensation

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37
Q

What do sebaceous glads secrete? Name 3 of its roles in the skin

A

Sebum = oily secretion

  • Nourishes hair shaft (stops from going dry)
  • Moisturises skin (too much = oily skin)
  • Water repellent
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38
Q

Name 2 types of sweat glands

A

Eccrine and apocrine

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39
Q

Where are eccrine sweat glands found?

A

In most areas of skin

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40
Q

Where are apocrine glands found?

A

Armpit, groin, around nipples

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41
Q

What is the function and role of eccrine sweat glands?

A

Pour sweat directly onto surface of skin

  • Important for thermoregulation
  • Antibacterial
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42
Q

What do apocrine sweat glands secrete, and how?

A

Sticky/oily/odorous secretions poured onto base of hair follicle, then to skin

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43
Q

What influences apocrine sweat glands? (give an example)

A

Influenced by hormones (e.g. breastmilk)

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44
Q

What function do nails serve?

A

○ Backboard to fingertips for receptors to be pressed against and activated

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45
Q

Name 5 things that happen in the skin during aging

A
  • Epidermis becomes thin (stratum basale dividing less rapidly, less cells to replenished)
  • Dermis becomes thinner (reduced collagen -> less strength -> wrinkling)
  • Slower repair
  • Drier epidermis (thin .: less blood, nutrients .: less sebum)
  • Impaired cooling (less sweat)
  • Less pigmentation (low melanin = pale skin, grey hair)
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46
Q

How does smoking accelerate aging? (3)

A
  • Chemicals target dermis -> damages collagen and elastin
  • Nicotine reduces blood circulation in dermis .: affects other layers of the skin
  • Poor wound healing, acne, skin and oral cancers
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47
Q

Where is melanin produced?

A

In melanocytes in the stratum basale

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48
Q

How is melanin transported towards the surface of the skin?

A

In vesicles called melanosomes that move/float up between gaps in cells until shed by the stratum conium

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49
Q

What is a mole?

A

cluster of melanocytes, produced in bulk from sun exposure

50
Q

What are freckles?

A

melanocytes overproducing melanosomes, over-production triggered by sun exposure

51
Q

Why is vit D needed in the body?

A

Leads to production of calcitriol which is essential for normal calcium metabolism and .: bone hardness, also mood regulation

52
Q

What happens if not enough vit D?

A

Rickets (bowleg)

53
Q

Explain why highly pigmented people more susceptible to vit D deficiency at extreme latitudes.

A

Melanin blocks out the little UV there is .: don’t meet UV requirements for vit D synthesis

54
Q

Where/who/when is rickets most common?

A
  • In NZ, UK overrepresented in maori, pasifika, asian, black populations
  • In winter/spring
  • In south island compared to north
55
Q

Describe basal cell carcinoma

A
  • Common, relatively benign
    • Originates in stratum basale
    • Spread is rare
56
Q

Describe malignant melanoma

A
  • Rare, but deadly if not treated
  • Originates in melanocytes
  • Uncontrollable growth, release of defective melanin in vesicles that can travel around body
  • Spreads anywhere, can have tumors on organs
  • Fatality depends on thickness of melanoma/tumor
57
Q

Where is the ink of a tattoo depositied?

A

Deposited into dermis (not epidermis, which is shed), and absorbed by immune cells

58
Q

Why do tattoos hurt?

A

because nerve endings and receptors in dermis layer

59
Q

Give an example a component of the skin corresponding to each tissue type

A

Muscular - erector pili muscle
Nervous - nerve fibres in dermis
Connective - blood
Epithelial - epidermis

60
Q

Name the 5 selected receptors of the skin

A
  1. free nerve endings
  2. tactile discs
  3. tactile corpuscles
  4. lamellar corpuscles
  5. bulbous corpuscles
61
Q

Describe the basic structure of free nerve endings

A
  • Unmyelinated (not always), small diameter fibres
  • Usually have small swellings at distal ends = sensory terminals
  • Have different types of receptors
62
Q

Are free nerve endings myelinated or unmyelinated?

A

Generally unmyelinated, but can be myelinated

63
Q

What is a sensory terminal?

A

The small swelling at the distal end of a free nerve ending

64
Q

What stimuli do free nerve endings give info about?

A

· Temp
· Pain
· Some movement and pressure (e.g. touch)
· Some wrap around hair follicles (peritrichial endings) - light receptors that detect bending of hair (e.g. mosquito)

65
Q

How do free nerve endings conduct a signal to the CNS?

A

If correct stimuli, receptors act as cation channel (Na+ and Ca2+ into cell -> depolarise -> AP to central nervous system)

66
Q

What are tactile discs, and where do you find them?

A

Free nerve endings in deepest layer of epidermis

67
Q

What are tactile discs associated with?

A

Associated with tactile epithelial cells called Merkel discs (detect the stimuli, relay to sensory nerve ending, for AP)

68
Q

Where in the body are tactile discs abundant? Why?

A

Abundant in fingertips and very small receptive fields, good for two point discrimination

69
Q

What are tactile discs sensitive to?

A

· texture, shape and edges

· fine touch and light pressure

70
Q

Where in the skin are tactile corpuscles found?

A

In the dermal papillary layer

71
Q

Describe the structure of tactile corpuscles

A

Spiralling, branching nerve terminals associated with Schwann cells (not making myelin), then surrounded by capsule

72
Q

How do tactile corpuscles generate an AP?

A

Pressure causes deformation of capsule, allows Na+ to enter -> AP

73
Q

What is the difference between tactile discs and tactile corpuscles?

A

tactile discs differentiate between smooth and rough, whereas tactile corpuscles differentiate between smooth and smooth or rough and rough

74
Q

What are tactile corpuscles sensitive to?

A

• Fine/discriminative touch
○ E.g. braille, objects moving over skin
• Light pressure
• Low frequency vibration

75
Q

Where are lamellar corpuscles found?

A

Scattered deep in dermis and hypodermis

76
Q

Describe the structure of lamellar corpuscles

A

Single dendrite lying within concentric layers of collagen fibres produced and surrounded by specialised fibroblasts.

77
Q

What separates layers of collagen fibres in lamellar corpuscles?

A

gelatinous interstitial fluid

78
Q

What is the purpose of interstitial fluid in lamellar corpuscles?

A

Transmit force/pressure

79
Q

How do lamellar corpuscles generate an AP?

A

Deformation of capsule opens pressure sensitive Na+ channels in sensory axon -> depolarisation -> AP

80
Q

Why are lamellar corpuscles ‘fast adapting’?

A

After deformation of capsule, inner layers covering axon terminal ‘relax’ quickly so APs discontinued

81
Q

What are lamellar corpuscles sensitive to?

A

· Deep pressure (when first applied)
· Also vibration because rapidly adapting/reset quickly
○ Optimal stimulation frequency is around 250Hz (which is similar to frequency range of generated upon fingertips by textures comprising features < 1 μM)

82
Q

Where are bulbous corpuscles located?

A

In dermis and subcutaneous tissue

83
Q

Describe the structure of bulbous corpuscles

A
  • Network of nerve endings intertwined with a core of collagen fibres that are continuous with those of the surrounding dermis. Capsule surrounds entire structure
84
Q

What are bulbous corpuscles sensitive to?

A

sustained deep pressure and stretching or distortion of the skin

85
Q

Bulbous corpuscles are important for signalling…

A

…continuous states of deformation of tissues, such as heavy prolonged touch and pressure signals, as well as proprioception when found in joint capsules

86
Q

What is the function of precapillary sphincters?

A

Contract/relax to control blood flow into capillary beds

87
Q

What tissue primarily makes up the walls of arteries?

A

Smooth muscle

88
Q

What is the function of smooth muscle in the walls of blood vessels?

A
  • constrict or dilate to change amount of blood flow to skin

- Important in thermoregulation

89
Q

What controls smooth muscle?

A

The SNS

90
Q

How does an increase in nerve signals result in blood vessel constriction?

A

Nerves release noradrenaline, binds to alpha1 adrenergic receptors on vascular smooth muscle in skin = increase [Ca2+] inside cell = more cross bridges = more contraction

91
Q

What is the range for regular core body temp?

A

36.5 - 37.5˚C

92
Q

When does core body temp increase?

A

exercising, fever

93
Q

What happens if core body temp too high?

A

proteins denature, seizures, convulsions, cell damage, death

94
Q

When is core body temp lower?

A

if cold, low metabolic rate

95
Q

What happens if core body temp too low

A

loss of muscle control, disorientation, coma, death

96
Q

Name the 4 heat transfer mechanisms

A

Radiation
Conduction
Convection
Evaporation

97
Q

What is radiation?

A

Heat transmitted to surrounding environment from anything at >0˚

98
Q

What is conduction?

A

transmission of heat to another media/object outside body along a gradient

99
Q

What is convection?

A

moving the medium/air you’ve heated and replacing it with a cold medium

100
Q

What is evaporation?

A

when liquid evaporates from body, taking heat with it

101
Q

eccrine sweat glands are innervated by…

A

the sympathetic nervous system

102
Q

Describe the receptors on eccrine sweat glands (as a cooling mechanism)

A

Sympathetic cholinergic release ACh (rather than noradrenaline) onto muscarinic acetylcholine receptors (mAChRs) which are G-protein coupled receptors (GPCRs)

103
Q

What causes nervous sweat?

A

Activation of B adrenergic receptors, which are sensitive to adrenaline/noradrenalin

104
Q

What detects a change in core body temp?

A

heat and cold sensitive neurons (central thermoreceptors) in the preoptic area of hypothalamus

105
Q

Explain what happens when the heat loss centre is activated (4)

A

○ reduce SNS activation of a1 receptors on blood vessels in the skin (blood vessel dilation) = loose more heat from skin to environment [convection, conduction, radiation, evaporation if sweating]
○ Increase SNS cholinergic activation of mAChRs on sweat glands -> sweat [evaporation]
○ Increase resp rate -> more air across tongue, increases evaporation
○ Behavioural changes (e.g. shade, take off clothes, drink water etc.)

106
Q

Explain what happens to activate the heat loss centre

A

Central thermoreceptors detect that body temp > set point -> activate heat loss centre

107
Q

What happens when environmental temp ≥ body temp?

A

Radiation, conduction and convection are not effective heat loss mechanisms .: only option is to sweat (evaporation)

108
Q

List what happens when the heat gain centre is activated (5)

A 
Non-shivering thermogenesis
Shivering 
Uncoupling of oxidative phosphorylation
Countercurrent system
Increased Thyroxine production
109
Q

What is non-shivering thermogenesis? What is its function?

A

Release of hormones to increase BMR
Results in:
• Increased SNS activity and circulating adrenaline/noradrenaline from adrenal medulla
• Breaking down glycogen stores in liver/muscle = increased cellular metabolism

110
Q

What is shivering? What is its function?

A
  • Increased muscle tone
  • Activates muscle spindles
  • Agonist and antagonist muscles contract in oscillatory pattern

= heat from muscles

111
Q

Describe the uncoupling of oxidative phosphorylation

A

some animals/infants not moving around much/shivering, so brown fat mobilized (fat has good blood supply, lots of mitochondria -> break down produces heat instead of ATP)

112
Q

Describe the countercurrent system. What is its function?

A

Anatomical feature in limbs where arteries close to veins

  • Warm blood from artery transmits heat to cold blood coming back in vein
  • Not all heat is going to skin/being lost to environment
113
Q

Describe increased Thyroxine production

A
  • In response to TRH and TSH
  • Increases basal metabolic rate
  • In adults humans may take several weeks exposure to cold before thyroid reaches new level of thyroxine secretion
114
Q

When and how are arrector pili muscles activated?

A

Activated in very cold environments by the SNS (a1 receptors)

115
Q

What is the function of arrector pili muscles?

A
  • Draws hair shaft vertical

- Traps layer of air = insulation

116
Q

Goosebumps act as physiological feedforward by…

A

Skin receptors indicating cold environment, warning that core body temp will drop after a period of time, encouraging preemptive action (more clothes etc.)

117
Q

What non-physiological factor is important in maintaining homeostasis?

A

Behavioural mechanisms

118
Q

In 2nd and 3rd degree burns, the loss of the epidermis means that….

A

the body can’t retain water

119
Q

Tissue damage in 2nd and 3rd degree burns leads to…

A

lots of inflammatory mediators = leaky capillaries = lose fluid

120
Q

What are the concerns of severe burns that help remind us of normal skin function

A
  • Fluid loss -> dehydration and decreased BP -> hypovolemic shock
  • Loss of antimicrobial barrier -> infection/sepsis
  • Fluid evaporation from skin -> hypothermia

HUBS192 (5 decks)

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