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Semester 1 Body Logistics > L19: Skin structure and function > Flashcards

L19: Skin structure and function Flashcards

1
Q

What is the general structure of the skin?

A

Epidermis
Dermis
Hypodermis

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2
Q

What are the key features of each layer?

A

Epidermis→ superficial, stratified squamous kertinised epithelium, avascular, split into layers
Dermis→ Deeper, provides support for epidermis, contains connective tissue element, part of skin appendages, nervous structures and vascaulature
Hypodermis→loose connective tissue with adipose tissue, sweat and sebaceous glands and larger blood vessels

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3
Q

What is the function of the skin?

A
  • Protection against microbial attack
  • Prevention of fluid loss
  • Temperature regulation
  • Fine control of excretion and absorption
  • Regeneration of skin tissue
  • Sensation (fine touch and grip control)
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4
Q

What is the main structure of the hypodermis?

A

Fat cells
Loose connective tissue→ fibroblasts, macrophages, mast cells and fibres
Adipose tissue→ neurovascular bundle and lymphocytes

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5
Q

How does the thickness of the hypodermis vary between males and females?

A

Males→ thickest abdomen and shoulder
Females→ thickest in hips, thighs and buttocks
Both thick in palms of hands for cushioning
Thinning in ageing causes wrinkles to form and hypothermia

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6
Q

What are the functions of the hypodermis?

A
  • Provides energy store→ provides fuel for heat for cells under hypodermis
  • Insulation for heat generation
  • Shock absorber→ cushioning impact
  • Connects skin to underlying muscle and bone
  • Makes hormones
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7
Q

What is the structure of the dermis?

A

Between the hypodermis and epidermis
3 layers
- Papillary layer→ hold epidermis in place
- Reticular layer→ dense loose connective tissue
- Dermal papillae layer→ interdigitating between epidermal ridges

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8
Q

What are the functions of the dermis?

A

Contains hairs and sweat glands → thermoregulation
Contains sensory structures→ mechanoreceptors
Gives structure to skin

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9
Q

What is the structure of the epidermis?

A

Thin and thick skin
Thin→ four layer
Thick→ five layers
Laterally held together by adherens junction
Layers held together by desmosomes
Some nerve terminal found in these layers
NO blood vessels

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10
Q

What is the function of the epidermis?

A
  • Prevents water loss
  • Absorbs water
  • Prevent entry of pathogens
  • Synthesis keratin
  • Prevents underlying abrasion (loss of tissue)
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11
Q

What are the different layers of the skin?

A 
Come Lets Get Sun Burnt
Stratum Corneum (horny cell layer)
Stratum Lucidum (transparent layer)
Stratum Granulsum (granular layer)
Stratum Spinosum (spinous layer)
Stratum Basale (basal cell layer)
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12
Q

What is the stratum corneum?

A

Outermost cell layer
Made of squames (dead keratinocytes)
Thick on palms and soles of feet- prone to injury
Continuously shed

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13
Q

What is the stratum lucidum?

A

Transparent cell layer

Only on palms and soles of feet

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14
Q

What is the stratum granulosum?

A

Stratified squamous epithelium
Lamellar granules (filament associated proteins that assemble keratin fibrils and secrete them)
Tonofibrils (bundles of keratin filaments and keratohyalin granules) made by lamella bodies

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15
Q

What is the stratum spinous?

A

Cuboidal epithelium arranged in 3 layers (held together by desmosome)
Producers of lamellar bodies (keratin factories)
Cells contain golgi apparatus→ allowing proteins to be modified before secretion

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16
Q

What is the strantum basale?

A 
Layer of tall columnar epithelial cells 
Constantly renewed by keratinocytes by cell division 
Differentiate as they move upwards 
Make keratin filaments (tonofilaments)
Also has melanocytes→ produce melanin
17
Q

How is keratin synthesised?

A
  1. Stratum basale→ basal cell precursor to the keratinocyte, continuous mitosis pushes the cells superficially
  2. Stratum Spinosum produced of 8-10 layers of keratinocytes
  3. Keratinocytes begin to produce keratin→ water repellent and prevent water loss
  4. As new cells produced these cells are pushed into the stratum granulosum→ 3-5 layers of keratinocytes become flatter, cell membrane thicken
  5. Produce lots of keratin which is fibrous- keratohyaline accumulates as lamellar granules
  6. Cell organelle disintergrate and cells die leaving keratin, keratohyalin and cell membrane
  7. Keratinocytes in the stratum lucidum are dead and flattened and full of a protein which makes them transparent
  8. The stratum corneum becomes keratinized (15-30 cells), dead dry layer helps prevent dehydration, abrasion and penetration by microbes
18
Q

What do keratinocytes synthesis?

A

Keratin (fibrous proteins)
Contribute to strength of the epidermis
Main constituent of hair, nail and animal horns

19
Q

What is the normal transit time of a keratinocyte?

A

28-40 days

20
Q

What happens when the transit time of a keratinocyte if reduced?

A 
Diseases such as:
- Psoriasis
2-3 day transit time 
Silvery sclares 
- Hyperkeratosis 
Too much keratin on surface of skin
21
Q

What other cells are present in the epidermis?

A

Melanocytes
Langerhan cells
Merkel cells

22
Q

What do melanocytes do?

A

Produce melanin
Pigmentation of skin
Occurs at intervals in basal layer

23
Q

What do Langerhans cells do?

A

High specialised capacity to present antigens to T lymphocytes
Mediate immune reaction

24
Q

What do Merkel cells do?

A

Mechanoreceptor cell

Associated with sensory nerve endings

25
Q

What are the different types of skin?

A 
Hairy skin
Non hairy skin 
Thin skin 
Thick skin 
Thin tends to be hairy 
Thick tends to be non hairy 
(except: lips, back of ear, some areas of external genitalia)
26
Q

Where is non hairy thick skin normally located?

A

Palmar surface of hand
Plantar surface of the foot
Area between fingers and toes

27
Q

What is the structure of non hairy thick skin?

A 
Same layers as rest of body 
No hair, arrector pili muscles, no sebaceous glands
Thicker strata corneum 
Thinner dermis 
Increased density of mechanoreceptors
28
Q

What is the function of non hairy thick skin?

A

Prevent tissue loss due to abrasion
Increased friction between skin and surfaces
Increased sensation

29
Q

What are the main differences between thick non hair and thin hairy skin?

A

Thick non hairy

  • No hair follicles
  • No sebaceous glands
  • No arrector pili muscles
  • Pronounced ridges and furrows on surface
  • Regular shaped dermal papillae
  • Stratum lucidum often seen

Thin hairy

  • Presence of hair follicles
  • Presence of sebaceous glands
  • Presence of arrector pili muscles
  • Smaller ridges and furrows
  • Irregular dermal papillae
  • Stratum lucidum absent
30
Q

What are skin appendages?

A

Extras on the skin

  • Hairs
  • Arrector pili
  • Sebaceous glands
  • Sweat glands
  • Nails
31
Q

What are the different types of hair?

A

Lanugo- covers the developing fetus
Vellus- replaces lanugo→ short thin light coloured soft
Terminal- head, axillae, external genital region→ long, wide, dark coloured and coarse, produced by the actions of testosterone

32
Q

What are the functions of hair?

A

Thermoregulation
→ flat when temp normal range
→ erect when temp lower
→ partial UV barrier
Sexual attraction
→ Apocrone sweat gland secrete oils that attract the opposite sex
Sensation
→ Sensory nerve ending within the bulb- vibrations, physical interaction and air movement transmitted to CNA
Protection
→ Eyelashes and nasal hair prevent dust and pathogens from entering the body
→ Eyebrows reduce the amount of light and sweat from entering the eye
→ Axilla hair conducts sweat away from the body

33
Q

How does the arrector pili muscle work?

A
  • Smooth muscle fibres attached to papillary region of the dermis (origin) and hair bulb (insertion)
  • Contraction- goose bumps appearance
  • May also cause sebum release from sebaceous gland
34
Q

What are the different types of mechanoreceptrors?

A
  1. End bulbs→ thermoreceptors
  2. Free nerve endings→ register pain
  3. Tactile discs→ senses touch, pressure and texture
  4. Meissner corpuscle→ tapping and flicker movements
  5. Pacinian corpuscle→ vibration
  6. Ruffini’s corpuscle→ joint movement and tissue stretch
  7. Root hair plexus → vibrations in the hair shaft
35
Q

What are the nails made of?

A 
Alpha keratin
- Nail plate
- Nail matrix
- Nail bed
Grooves surrounding it
36
Q

What is the function of the nails?

A
  • Protection of distal phalanges
  • Enhances precise delicate movements
  • Enhances sensitivity of fingertips (nail itself has no nerve endings)
  • Tool for extended precision grip
37
Q

What is the function of the skin?

A
  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

Semester 1 Body Logistics (19 decks)

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