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Semester 1 - Body Logistics > 13. Skin > Flashcards

13. Skin Flashcards

(78 cards)

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1
Q

What are the 3 layers of skin?

A

Epidermis
Dermis
Hypodermis

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2
Q

What does the thickness of the hypodermis vary upon?

A

Upon different regions of the body and different people

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3
Q

In men, where is the hypodermis thickest in?

A

abdomen and shoulders

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4
Q

In women, where is the hypodermis thickest in and why?

A

hips, thighs, and buttocks- evolutionary advantage to store fat to produce milk

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5
Q

In both men and women where is the hypodermis relatively thick in?

A

palms of the hands and soles of feet - acts as a shock absorber

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6
Q

Where is the hypodermis found?

A

Lowest layer of skin

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7
Q

What is the hypodermis also know as?

A

sub-cutaneous layer

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8
Q

Describe the structure of the hypodermis

A
  • Mainly contains adipose tissue (some neurovascular bundles/lymphatics)
  • Loose connective tissue – fibroblasts/ macrophages/fibres/mast cells
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9
Q

What are the 5 functions of hypodermis?

A
  • Provides energy store – provides fuel to generate heat
  • Insulator for underlying muscle heat generation
  • Shock absorber – cushions impacts/protection for underlying structures e.g. think about fat on the buttocks when sitting
  • Connects skin to underlying muscle and bones
  • Makes hormones, e.g. leptin to control eating habits
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10
Q

Where is the dermis layer found?

A

Between epidermis and hypodermis

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11
Q

What is the dermis also know as and when combined with epidermis?

A

Corium AND with epidermis - cutis

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12
Q

Describe the structure of the dermis layer

A

Three layers
• Papillary - upper
• Reticular - lower - connective tissue
• Dermal papillae – interdigitating

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13
Q

What are the 3 functions of the dermis?

A
  • Contains hairs and sweat glands - thermoregulation
  • Contains sensory structures – special senses - touch
  • Gives structure to skin and so body shape
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14
Q

What is the location of the epidermis?

A

Outermost layer made of epithelial cells (keratinocytes)

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15
Q

Describe the structure of the epidermis

A
  • Four layers of cells in thin skin
  • Five layers in thick skin
  • Held together (laterally) by adherens junctions - layers held together by desmosomes
  • Some terminal nerve endings
  • NO blood vessels
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16
Q

What are the 5 functions of the epidermis?

A
  • Prevents water loss - can absorb water as well
  • Prevents entry to bacteria and parasites
  • Special cells that present pathogens to immune cells
  • Synthesis of keratin
  • Prevents underlying tissue loss due to abrasion
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17
Q

What are the 4/5 layers of the epidermis?

A
  1. Stratum corneum
  2. Stratum lucidum
  3. Stratum granulosum (granular layer)
  4. Stratum spinosum
  5. Stratum basale
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18
Q

Describe the stratum corneum layer

A
  • Outermost layer made of squames (dead keratinocytes)
  • Thick on palms and soles of feet – prone to injury
  • Continuously shed
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19
Q

Describe the Stratum lucidum

A
  • Only on palms and soles of feet

* Very thin layer

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20
Q

Describe the Stratum granulosum (granular layer)

A

• Stratified squamous epithelium
• contain Lamellar granules (filament-associated proteins that assemble keratin fibrils and secrete it)
• contain Tonofibrils (bundles of keratin filaments and keratohyalin granules)
made by lamellar bodies

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21
Q

Describe Stratum spinosum layer

A

• Cuboidal epithelium arranged in 3 layers (held together by
desmosomes)
• Producers of lamellar bodies (keratin factories)
• First time Golgi apparatus appears

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22
Q

Describe the Stratum basale (basal cell layer)

A
  • Tall columnar epithelial cells
  • Constantly renew keratinocytes by cell division
  • As daughter cells differentiate they move away from the epidermis-dermis junction -They lose their ability to divide
  • These make keratin filaments (tonofilaments)
  • Also home to the melanocytes – produce melanin
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23
Q

Describe the keratin synthesis pathway

A

Starting at the bottom:
• Basal cell (keratinocyte)has intermediate keratin filaments(tonofilaments)
• As it divides, it makes cuboidal epithelial cells called spinous cells - first see the appearance of lamellar bodies (keratin forming factories )and mitochondria
• As the spinous cells move further away from basal surface, they differentiate into granular cells which contain keratohyalin granules and the Golgi apparatus
• This is where keratin is layed out
• As the cells move away from the surface, they die out(apoptosis) but are held together by desmosomes
• As they move further away, proteins are produced which break down the desmosomes - the squames can seperate
• The keratin fibrils are now called tonofibrils

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24
Q

Which cells synthesise keratin?

A

Keratinocytes - lamellar bodies found in keratinocytes.

Keratinocytes are found in basal layer and different into granular cells as they move up towards the stratum corneum

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25
What are keratin the main constituents of ?
Hair, nail, animal horns
26
What is the normal transit time o a keratinocyte from basal layer to stratum corneum?
28-40 days
27
In which disease is the transit time reduced to 2-3 days?
Psoriasis
28
What does psoriasis result in?
• Psoriasis is a skin condition that causes red, flaky, crusty patches of skin covered with silver-coloured scales.
29
Describe what causes psoriasis
In individuals with psoriasis, the transit time from basal layer to stratum corneum is reduced. As a result, cells that have not yet fully matured accumulate in the stratum corneum and the outer layer of keratin, which is relatively thin is lost causing the signs of crusty red patches covered with silvery scales. The cells at the surface are also lost very quickly too as they are ‘rubbed’ off.
30
What are the 3 cells present in the epidermis?
Melanocytes Langerhan cells Merkel cells
31
What do melanocytes produce?
produce melanin, the main pigment that gives the skin its | colour produce more melanin
32
Are there more melanocytes in black or tanned skin?
No, Number of melanocytes not increased, but amount of melanin released, increased
33
What are langerhan cells?
highly specialised capacity to present antigens to T lymphocytes mediate immune reactions e.g. in allergic contact dermatitis
34
What are merkel cells?
mechanoreceptor cells associated with sensory nerve endings. They account for approximately 6% to 10% of the cells in the epidermis
35
What are the two types of skin?
Hairy, thin skin | Non hairy, thick skin
36
What are the exceptions to the rule of the two types of skin?
the lips, back of the ear, some areas of the external genitalia
37
Where are non hairy, thick skin found?
* Palmar surface of hand * Plantar surface of the foot * Area between fingers and toes (webs)
38
What is the structure of non hairy thick skin?
* Same as rest of body except: * NO hair, arrector pili muscles, no sebaceous glands * Thicker strata corneum * Thinner dermis * Increased density of mechanoreceptors
39
What are the 3 functions of non hairy skin?
* Prevent tissue loss due to abrasion * Increased friction between skin and surfaces * Increased sensation
40
What are the differences between thick non hairy skin and thin hairy skin?
> Thick skin have No hair follicles >thin skin have hair follicle >thick skin have no sebaceous glands > thin skin have sebaceous glands > thick skin have no arrector pili muscles >thin skin have arrector pili muscles >thick skin have pronounced ridges and furrows on surface >thin skin have smaller ridges and furrows > thick skin have regulate shaped dermal papillae > thin skin have irregular dermal papillae >in thick skin, stratum lucidum is often seen >in thin skin, stratum lucidum is absent
41
What are skin appendages?
Skin appendages are skin- associated structures that serve a particular function
42
Give 5 examples of skin appendage
``` Hairs Arrector pili Sebaceous glands Sweat glads Nails ```
43
What are the 3 different types of hair?
Lanugo Vellus Terminal
44
What is lanugo?
The hair that cover the devoloping fetus
45
What is vellus?
The hair that replaces lanugo
46
Describe the appearance of vellus
Short, thin, light coloured and soft (not | connected to sebaceous gland)
47
Where is terminal hair found?
head (scalp and eyebrows, nasal passage), axillae, external genital region
48
Describe the appearance of terminal hair
Long, wide, dark coloured and coarse
49
What results in the production of terminal hair?
actions of testosterone
50
What are the 4 functions of hair?
Thermoregulation Sexual attraction Sensation Protection
51
How are hairs involved in thermoregulation?
• Hair lays flat when body temperature is within normal range or elevated • Hair stands erect when body temperature is lower than normal range -Arrector pili muscle contracts when stimulated by sympathetic fibres from the autonomic nervous system • Also acts a partial barrier to UV rays (scalp)
52
How are hairs involved in sexual attraction?
• Hair style can be alluring! • Apocrine sweat glands secrete oils (pheromones) that attract the opposite sex. Hairs trap these oils and accentuate their pungency
53
How are hairs involved in sensation?
Hairs have sensory nerve endings within the bulb. Air movement, physical interaction, vibrations transmitted to the bulb sensed and transmitted to CNS. Provides sensory awareness
54
How are hairs involved in protection?
* Eyelashes and nasal hair prevent dust and pathogens from entering the body * Eyebrows reduce the amount of light and sweat from entering the eyes * Axilla hair acts as a conduit to conduct sweat away from the body
55
What are arrector pili muscles?
The arrector pili muscles are small muscles attached to hair follicles in mammals. They consist of smooth muscle fibres attached to papillary region of the dermis (origin) and hair bulb (insertion).
56
What is the role of arrector pili muscle?
* Involved in moving hair follicle * It is a skeletal muscle cell * attached to bulb of bottom of hair follicle * When it contracts, it moves bulb towards itself which raises the hair so it stands up erect • Fight or flight response’ or ‘cold’ causes involuntary contraction - ‘goose bumps’ • May also induce sebum release from sebaceous gland - advantage in flight or fight as more slippery
57
What are the 7 mechanoreceptors in skin?
1. End bulbs – thermoreceptor – register temperature 2. Free nerve endings have nociceptors – register pain 3. Tactile discs 4. Meissner corpuscle 5. Pacinian corpuscle 6. Ruffini’s corpuscle 7. Root hair plexus
58
What do thermoreceptors detect?
Temperature
59
What doe nociceptors register?
Pain
60
What do tactile discs sense?
touch, pressure and texture
61
What are the two types of tactile discs found in hairy and non hairy skin?
Merkel in non-hairy skin | Meissner in hairy skin
62
What does the meissner corpuscle detect?
Tapping and flicker movements
63
What’d ones the pacinian corpuscle detect?
Vibration
64
What does the Ruffini’s corpuscle detect?
joint movements and tissue stretch
65
What does the root hair plexus detect?
vibrations in the hair shaft
66
Describe the location of nails
Distal surface of phalanges (fingers and toes)
67
Describe the structure of nails
Consists solely of alpha keratin and has: nail plate, the nail matrix and the nail bed below it, and grooves surrounding it
68
What are the 4 functions of nails?
• Protection of distal phalanx and surrounding soft tissues from (e.g. pulling out a splinter in one's finger), and certain cutting or scraping actions • Enhances precise delicate movements of the distal digits through counter-pressure exerted on the pulp of the finger • Enhancing the sensitivity of the fingertip (even though the nail itself has no nerve endings) • As a tool, enabling the so-called "extended precision grip"
69
What is the growth of nails correlated with?
Length of phalanx
70
What are the 8 functions of the skin?
1. Protection and repair 2. Temperature regulation and excretion of waste products 3. Lubrication 4. Storage 5. Vitamin d synthesis 6. Absorption 7. Aesthetics 8. Sensation
71
How is skin involved in protection and repair?
epidermis by keratinocytes and UV protection by melanocytes invasion by Langerhans cells papillary dermis by fibroblasts (wound healing) reticular dermis/hypodermis by fibroblasts/mast cells and macrophages
72
How is the skin involved in Temperature regulation and excretion of waste products?
Sweat glands – urea, sodium chloride and water, some CO2
73
How is skin involved in lubrication
Sebaceous glands release oil onto the surface (also acts as water barrier)
74
How I is the skin involved in storage?
White adipose cells provide lipids for energy
75
How is skin included in vitamin d synthesis ?
Cholecaliciferol produced in the skin is converted into 25-hydroxyl cholecalciferol (25-OH) by the liver and then into 1, 25-hydroxyl cholecalciferol (1,25 OH) VitD (the active vitamin) by the kidney
76
How is the skin involved in absorption?
Absorbs small amounts of water and O2 (some drugs – steroids can be applied and absorbed through the skin)
77
How is the skin involved in aesthetics?
Skin as a mode of communication or attraction (tattoos, piercing, hair-styles, etc.)
78
How is the skin involved in sensation
Specialised structures call mechanoreceptors (pain, pressure, touch, arousal, etc.)

Semester 1 - Body Logistics (16 decks)

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