Skin Flashcards
(83 cards)
1
Q
3 layers of the skin
A
epidermis
dermis
hypodermis
2
Q
cutaneous layer
A
epidermis
dermis
3
Q
subcutaneous layer
A
hypodermis
deep to the cutaneous layer
4
Q
epidermis
A
stratified barrier
mostly keratinocytes
no blood circulation (avascular)
outermost layer of the skin
5
Q
dermis
A
protein fibres for strength
vascular (nourishes epidermis)
6
Q
epidermal ridge
A
junction of dermis and epidermis
wavy to increase surface area for maximum nourishment of the epidermis via blood vessels
7
Q
epithelia
A
epithelial tissue
dominant tissue of the skin
8
Q
types of epithelia
A
simple or stratified (stacked, multiple)
- squamous
- cuboidal
- columnar
9
Q
squamous
A
long and flat
10
Q
cuboidal
A
cube shaped
11
Q
columnar
A
long, tall, column like
12
Q
layers of epidermis
A
stratum corneum
stratum granulosum
stratum spinosum
stratum basale
13
Q
stratum corneum
A
horny layer
dead, dried out hard cells without nuclei (keratin)
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
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
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
17
Q
desmosomes
A
anchors neighbouring cells in epidermis
18
Q
hemidesmosomes
A
anchors stratum basale to the dermis
19
Q
thick skin
A
found on palms of hands and soles of feet
no hair
extra epidermal layer - stratum lucidum (under corneum)
20
Q
dermis
A
situated below the epidermis and anchors via hemidesmosomes
not shed
divided into two layers
21
Q
layers of dermis
A
papillary layer
reticular layer
both layers contain blood vessels, lymphatics, sensory nerve fibres and accessory structures
22
Q
papillary layer
A
consists of highly vasculated tissues (for nourishment)
23
Q
reticular layer
A
‘mesh-like’ structure of collagen and elastin fibres for strength
24
Q
plexuses of the dermis
A
cutaneous plexus
subpapillary plexus
25
cutaneous plexus
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
26
subpapillary plexus
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
27
hypodermis
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
28
first degree burns
- 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
29
second degree burns - normal
- epidermis + varying amounts of dermis
- painful, moist, red and blistered
usually heals in about 1 - 2 weeks (needs good dressings)
30
second degree burns - deeper
- 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
31
third degree burns
- 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
32
accessory structures
hair
sweat glands
receptors
nails
33
hair
- 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
34
sweat glands
- 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
receptors
tactile
lamellar
bulbous
36
nails
- protect fingertips/toes
- enhance sensation
- sensory receptors require deformation
37
skin aging
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
the melanin pigment absorbs __ light, protecting cells from __ damage
UZ, UV
39
melanin
pigment of the skin
produced in melanocytes
transferred to epidermal cells by melanosomes
40
melanosomes
vesicles containing melanin
| found throughout the epidermis - shed with keratinocytes
41
melanocytes
only found in the stratum basale - not shed
| density varies throughout body and through time
42
mole
cluster of melanocytes
| over-proliferation can be caused by sun exposure
43
freckle
melanocytes overproducing melanosomes
| over-production triggered by sun exposure
44
vitamin D
- 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
skin cancers
basal cell carcinoma
| malignant melanoma
46
basal cell carcinoma
common but relatively benign
originates stratum basale
metastasis (spread) is rare
47
malignant melanoma
rare but deadly if not treated
originates in melanocytes (pigmented)
highly metastatic
mortality rate dependent upon tumour
48
tattoo
```
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
types of tattoo
trauma - decorative)
| cosmetic - e.g. brows
50
skin receptors (5)
```
free nerve endings
Tactile (Merkel) discs
Tactile (Meissner) corpuscles
Lamellar (Pacinian) corpuscles
Bulbous corpuscles (Ruffini's endings)
```
51
free nerve endings
| features of structure
mostly unmyelinated small diameter fibres
some myelinated small diameter fibres
usually have sensory terminals (small swellings as distal ends)
sensory terminals have receptors
52
free nerve endings
| functions
receptors function as cation channels --> depolarisation --> AP's
53
free nerve endings
| respond to
temperature
painful stimuli
some to itch
some wrap around hair follicles (peritrichial endings) acting as light touch receptors which detect bending of hairs
54
Tactile (Merkel) discs
| features of structure
free nerve endings located in deepest layer of epidermis
55
Tactile (Merkel) discs
| function
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
Tactile (Merkel) discs
| respond to
```
sensitive to an object's physical features:
texture
shape
edges
fine touch
light pressure
```
57
Tactile (Meissner) corpuscles
| features of structure
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
Tactile (Meissner) corpuscles
| function
deformation of capsule triggers entry of Na+ ions into nerve terminal --> AP
senses delicate 'fine' or discriminative touch
59
Tactile (Meissner) corpuscles
| feels
sensitive to:
shape and textural changes in exploratory touch e.g. reading Braille text, light pressure, low frequency vibration (2 to 80 Hz)
60
Lamellar (Pacinian) corpuscles
| features of structure
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
Lamellar (Pacinian) corpuscles
| function
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
Lamellar (Pacinian) corpuscles
| responds to
deep pressure
| vibration because rapidly adapting
63
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Bulbous corpuscles (Ruffini's endings)
features of structure
```
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
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Bulbous corpuscles (Ruffini's endings)
function
```
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
```
Bulbous corpuscles (Ruffini's endings)
responds to/feels
```
sensitive to sustained deep pressure and stretching or distortion of the tissues such as have prolonged touch and pressure signals
66
skin blood flow
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
body temperature regulation
core set temp is between 36.5˚ and 37.5˚C for normal function
68
primary mechanisms of heat transfer
radiation
conduction
convection
evaporation
69
radiation
heat radiates from us, is emitted from our skin
70
conduction
when we are in contact with something our heat transfers to the object until it is the same temperature as us
71
convection
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
evaporation
our sweat evaporates into the surroundings
73
radiation, conduction and convection are not effective heat loss mechanisms when...
environmental temp ≥ body temp
74
heat gain centre
| activated by
central thermoreceptors detecting temperatures below 'set point'
75
heat generating mechanisms
shivering
non-shivering thermogenesis
increased thyroxine
76
shivering
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
non-shivering thermogenesis
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
increased thyroxine
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
arrector pili muscles
| structure
smooth muscle innervated by SNS (α1 receptors)
| attach hair follicle to upper dermis
80
arrector pili muscle
| function
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
burns and fluid replacement
for 2nd and 3rd degree burns, as you have lost the epidermal layer, you will be losing fluid to the environment
82
potential complication of severe burns
dehydration and hypovolemic shock
infection/sepsis
hypothermia
83
severe burns can also cause dysfunction in other systems
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electrolyte imbalances
hypermetabolism
gastrointestinal ulceration
renal failure
respiratory dysfunction
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