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HUBS192 > Skin > Flashcards

Skin Flashcards

1
Q

3 layers of the skin

A

epidermis
dermis
hypodermis

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2
Q

cutaneous layer

A

epidermis

dermis

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3
Q

subcutaneous layer

A

hypodermis

deep to the cutaneous layer

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4
Q

epidermis

A

stratified barrier
mostly keratinocytes
no blood circulation (avascular)
outermost layer of the skin

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5
Q

dermis

A

protein fibres for strength

vascular (nourishes epidermis)

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6
Q

epidermal ridge

A

junction of dermis and epidermis

wavy to increase surface area for maximum nourishment of the epidermis via blood vessels

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7
Q

epithelia

A

epithelial tissue

dominant tissue of the skin

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8
Q

types of epithelia

A

simple or stratified (stacked, multiple)

  • squamous
  • cuboidal
  • columnar
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9
Q

squamous

A

long and flat

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10
Q

cuboidal

A

cube shaped

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11
Q

columnar

A

long, tall, column like

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12
Q

layers of epidermis

A

stratum corneum
stratum granulosum
stratum spinosum
stratum basale

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13
Q

stratum corneum

A

horny layer

dead, dried out hard cells without nuclei (keratin)

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14
Q

stratum granulosum

A

granular layer
contains granules that promote dehydration of the cell, crosslinking of keratin fibre, waxy material is secreted into the intercellular spaces

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15
Q

stratum spinosum

A

spinous, spiny or prickle cell layer
intercellular bridges called desmosomes link the cells together, the cells become increasingly flattened as they move upward

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16
Q

stratum basale

A

basal layer
columnar (tall) regenerative cells, as the basal cell divides, a daughter cell migrates upwards to replenish the layer above

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17
Q

desmosomes

A

anchors neighbouring cells in epidermis

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18
Q

hemidesmosomes

A

anchors stratum basale to the dermis

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19
Q

thick skin

A

found on palms of hands and soles of feet
no hair
extra epidermal layer - stratum lucidum (under corneum)

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20
Q

dermis

A

situated below the epidermis and anchors via hemidesmosomes
not shed
divided into two layers

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21
Q

layers of dermis

A

papillary layer
reticular layer

both layers contain blood vessels, lymphatics, sensory nerve fibres and accessory structures

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22
Q

papillary layer

A

consists of highly vasculated tissues (for nourishment)

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23
Q

reticular layer

A

‘mesh-like’ structure of collagen and elastin fibres for strength

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24
Q

plexuses of the dermis

A

cutaneous plexus

subpapillary plexus

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25
Q

cutaneous plexus

A

network of blood vessels present at the junction of the dermis/hypodermis, supplies the hypodermis, deeper dermis, including the capillaries for hair follicles and sweat glands

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26
Q

subpapillary plexus

A

branches from the cutaneous plexus,
lies deep to the papillary layers of the dermis,
network of blood vessels providing O2 and nutrients to the upper dermis and epidermis

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27
Q

hypodermis

A

the subcutaneous layer
not considered part of the skin
dominated by adipocytes that produce subcutaneous fat
the subcutaneous fat stores energy and provides insulation
common site of injections using hypodermic needles

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28
Q

first degree burns

A
  • superficial i.e. only involves the outer layers of the epidermis
  • red/pink, dry, painful
  • skin remains a water and bacterial barrier
  • usually heals in 3 - 10 days
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29
Q

second degree burns - normal

A
  • epidermis + varying amounts of dermis
  • painful, moist, red and blistered
    usually heals in about 1 - 2 weeks (needs good dressings)
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30
Q

second degree burns - deeper

A
  • may include whiteish, waxy looking areas
  • hair follicles, sweat glands may remain intact
  • usually heal in a month
  • may have some loss of sensation and scarring
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31
Q

third degree burns

A
  • full thickness burns i.e. extend into subcutaneous tissue and may involve muscle and bone
  • varied colour from waxy white through to deep red or black
  • hard, dry and leathery
  • no pain in these areas as sensory nerve endings are destroyed
  • may require skin grafting
  • weeks to regenerate + scarring
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32
Q

accessory structures

A

hair
sweat glands
receptors
nails

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33
Q

hair

A
  • found all over the body except palms of hands, soles of feet and lips
  • made of dead, keratinised cells produced inside a hair follicle
  • contraction of the arrector pili muscle results in ‘goose bumps’, improves insulation
  • root hair plexus - collection of sensory nerves at the base of each hair follicle, heightened sensation
  • sebaceous glands = produce oily secretion (sebum), nourishes hair shaft and naturally moisturises skin, water repellent, blocked hair follicles + infection due to increased sebum production leads to acne, lanolin (sheep sebum) = purified and used commercially in skin care products
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34
Q

sweat glands

A
  • eccrine = found in most areas of the skin, pour watery secretions directly onto the skin surface, important in thermoregulation and excretion, some antibacterial action
  • apocrine = found in armpit, groin and around the nipples, secrete sticky/oily and at times, potentially odoroud secretions into the base of the hair follicle, influenced by hormones e.g. breastmilk
35
Q

receptors

A

tactile
lamellar
bulbous

36
Q

nails

A
  • protect fingertips/toes
  • enhance sensation
  • sensory receptors require deformation
37
Q

skin aging

A

epidermis begins to thin
dermis thins too as reduced collagen (sagging/wrinkling)
slower skin repair
drier epidermis due to less sebum as less nourishment (blood supply)
impaired cooling as less sweat
less pigmentation = pale skin, grey hair

38
Q

the melanin pigment absorbs __ light, protecting cells from __ damage

A

UZ, UV

39
Q

melanin

A

pigment of the skin
produced in melanocytes
transferred to epidermal cells by melanosomes

40
Q

melanosomes

A

vesicles containing melanin

found throughout the epidermis - shed with keratinocytes

41
Q

melanocytes

A

only found in the stratum basale - not shed

density varies throughout body and through time

42
Q

mole

A

cluster of melanocytes

over-proliferation can be caused by sun exposure

43
Q

freckle

A

melanocytes overproducing melanosomes

over-production triggered by sun exposure

44
Q

vitamin D

A
  • essential for normal calcium metabolism and strong bones
  • deficiency causes rickets and affects mood
  • UV exposure in skin is required for vitamin D synthesis
  • likely explains the greater incidence of lightly pigmented skin at higher letitudes
45
Q

skin cancers

A

basal cell carcinoma

malignant melanoma

46
Q

basal cell carcinoma

A

common but relatively benign
originates stratum basale
metastasis (spread) is rare

47
Q

malignant melanoma

A

rare but deadly if not treated
originates in melanocytes (pigmented)
highly metastatic
mortality rate dependent upon tumour

48
Q

tattoo

A 
artificial pigmentation (usually ink) deposited deep within the skin into the dermal layer so is not shed, allowing it to be permanent
ink is captured (but not broken down) inside immune cells/scar tissue
49
Q

types of tattoo

A

trauma - decorative)

cosmetic - e.g. brows

50
Q

skin receptors (5)

A 
free nerve endings
Tactile (Merkel) discs
Tactile (Meissner) corpuscles
Lamellar (Pacinian) corpuscles
Bulbous corpuscles (Ruffini's endings)
51
Q

free nerve endings

features of structure

A

mostly unmyelinated small diameter fibres
some myelinated small diameter fibres
usually have sensory terminals (small swellings as distal ends)
sensory terminals have receptors

52
Q

free nerve endings

functions

A

receptors function as cation channels –> depolarisation –> AP’s

53
Q

free nerve endings

respond to

A

temperature
painful stimuli
some to itch
some wrap around hair follicles (peritrichial endings) acting as light touch receptors which detect bending of hairs

54
Q

Tactile (Merkel) discs

features of structure

A

free nerve endings located in deepest layer of epidermis

55
Q

Tactile (Merkel) discs

function

A

associated with large disc shaped epidermal (Merkel) cells, communication between the tactile epithelial cell and nerve ending possibly via serotonin (5HT)
very small receptive fields = good for two point discrimination

56
Q

Tactile (Merkel) discs

respond to

A 
sensitive to an object's physical features:
texture
shape
edges
fine touch
light pressure
57
Q

Tactile (Meissner) corpuscles

features of structure

A

located in papillary layer of dermis, especially in hairless skin
encapsulated = spiraling/branching unmyelinated sensory terminals surrounded by modified Schwann cells and then by a thin oval fibrous connective tissue capsule

58
Q

Tactile (Meissner) corpuscles

function

A

deformation of capsule triggers entry of Na+ ions into nerve terminal –> AP
senses delicate ‘fine’ or discriminative touch

59
Q

Tactile (Meissner) corpuscles

feels

A

sensitive to:
shape and textural changes in exploratory touch e.g. reading Braille text, light pressure, low frequency vibration (2 to 80 Hz)

60
Q

Lamellar (Pacinian) corpuscles

features of structure

A

deep in dermis and hypodermis
single dendrite lying within concentric layers of collagen fibres and specialised fibroblasts
layers separated by gelatinous interstitial fluid
dendrite essentially isolated from stimuli other than deep pressure

61
Q

Lamellar (Pacinian) corpuscles

function

A

deformation of capsule opens pressure sensitive Na+ channels in sensory axon, inner layers covering axon terminal ‘relax quickly so AP is discontinued (rapidly adapting)
stimulated by deep pressure

62
Q

Lamellar (Pacinian) corpuscles

responds to

A

deep pressure

vibration because rapidly adapting

63
Q 
Bulbous corpuscles (Ruffini's endings)
features of structure
A

located in dermis and subcutaneous tissue
network of nerve endings intertwined with a core of collagen fibres that are continuous with those of the surrounding dermis
capsule surrounds entire structure
also found in joint capsules and fingernails (high density)

64
Q 
Bulbous corpuscles (Ruffini's endings)
function
A

important for signaling continuous states of deformation of the tissues such as have prolonged touch and pressure signals
helps signal degree of joint rotation proprioception)
may have a role in monitoring slippage of objects across surface of the skin

65
Q 
Bulbous corpuscles (Ruffini's endings)
responds to/feels
A

sensitive to sustained deep pressure and stretching or distortion of the tissues such as have prolonged touch and pressure signals

66
Q

skin blood flow

A

smooth muscle in walls of arteries and precapillary sphincters innervated by the SNS
noradrenaline acts on α1 adrenergic receptors on this vascular smooth muscle in the skin, GPCR’s coupled to intracellular 2nd messengers –> increased intracellular Ca2+ –> constriction = reduced skin blood flow
regulates body heat by restriction and dilation of blood vessels

67
Q

body temperature regulation

A

core set temp is between 36.5˚ and 37.5˚C for normal function

68
Q

primary mechanisms of heat transfer

A

radiation
conduction
convection
evaporation

69
Q

radiation

A

heat radiates from us, is emitted from our skin

70
Q

conduction

A

when we are in contact with something our heat transfers to the object until it is the same temperature as us

71
Q

convection

A

when our heat heats the media surrounding us then this moves away and more cooler media is replaced so we keep losing heat as the surrounding media is constantly using ours

72
Q

evaporation

A

our sweat evaporates into the surroundings

73
Q

radiation, conduction and convection are not effective heat loss mechanisms when…

A

environmental temp ≥ body temp

74
Q

heat gain centre

activated by

A

central thermoreceptors detecting temperatures below ‘set point’

75
Q

heat generating mechanisms

A

shivering
non-shivering thermogenesis
increased thyroxine

76
Q

shivering

A

increased tone of muscles
when tone rises above critical level, shivering begins due to oscillatory contractions of agonist and antagonist muscles mediate by muscle spindles (stretch receptors)

77
Q

non-shivering thermogenesis

A

increased sympathetic nerve activity and increased circulating adrenaline/noradrenaline from adrenal medulla
increased cellular metabolism e.g. increased glycogenolysis in liver and muscle
‘uncoupling’ of oxidative phosphorylation i.e. heat produced instead of ATP (occurs in ‘brown fat’ particularly in infants)

78
Q

increased thyroxine

A

in response to TRH and TSH
increases basal metabolic rate
in adult humans may take several weeks exposure to cold before thyroid reaches new level of thyroxine secretion

79
Q

arrector pili muscles

structure

A

smooth muscle innervated by SNS (α1 receptors)

attach hair follicle to upper dermis

80
Q

arrector pili muscle

function

A

contraction pulls hairs upright and dimples skin –> goose bumps
compresses sebaceous glands which lubricates skin
if you are a hairy mammal, this traps a layer of warm air around skin and makes you look bigger, scarier and more formidable
physiological feed forward

81
Q

burns and fluid replacement

A

for 2nd and 3rd degree burns, as you have lost the epidermal layer, you will be losing fluid to the environment

82
Q

potential complication of severe burns

A

dehydration and hypovolemic shock
infection/sepsis
hypothermia

83
Q

severe burns can also cause dysfunction in other systems

A 
electrolyte imbalances
hypermetabolism
gastrointestinal ulceration
renal failure
respiratory dysfunction

HUBS192 (2 decks)

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