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Body Logistics Revision > 19 - Skin > Flashcards

19 - Skin Flashcards

1
Q

What are the 4 layers of the epidermis (outermost to innermost)?

A

Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale

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2
Q

What are the three layers of the dermis?

A 
Papillary dermis (upper)
Reticular dermis (lower)
Dermal Papillae (interdigitating)
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3
Q

What type of connective tissue makes up the dermis?

A

Irregular dense connective tissue

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4
Q

What structures are found in the dermis?

A
  • Hair follicles
  • Arrector pili muscles
  • Sweat glands
  • Sebaceous glands
  • Blood vessels, nerves and lymphatics
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5
Q

What skin layer lies beneath the dermis?

A

Hypodermis

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6
Q

How does the thickness of the hypodermis vary between men and women?

A

Men - thickest in abdomen and shoulders
Women - thickest in hips, thighs and buttocks

Thick on palms of hands in both sexes

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7
Q

What is the hypodermis and what does it do?

A
  • Sub-cutaneous layer (not always considered part of skin)
  • Mainly adipose tissue (with some neurovascular bundles) and loose connective tissue
  • Energy store
  • Insulates underlying muscle
  • Shock absorber to protect underlying structures
  • Connects skin to underlying muscle/bone
  • Makes hormones
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8
Q

What are the functions of the dermis?

A
  • Thermoregulation - hairs and sweat glands
  • Special senses (touch) - sensory structures
  • Gives structure to the skin and so body shape
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9
Q

What type of epithelial cells make up the epidermis?

A

Keratinised stratified squamous epithelium

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10
Q

What is the structure of the epidermis?

A
  • Keratinised stratified squamous epithelium
  • Four or five layers (depends on thickeness)
  • Held together laterally by adherens junctions
  • Some terminal nerve endings but no blood vessels
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11
Q

What is the structure of the stratum corneum (outermost layer)?

A
  • Made of dead keratinocytes
  • Thick on palms and soles of feet
  • Continuously shedded
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12
Q

What is the structure of the stratum granulosum (2nd layer down)?

A
  • Stratified squamous epithelium
  • Lamellar granules (proteins that assemble keratin fibrils)
  • Tonofibrils (bundles of keratin filaments) made by lamellar bodies
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13
Q

What is the structure of the stratum spinosum (3rd layer down)?

A
  • Cuboidal epithelium arranged in 3 layers
  • Held together by desmosomes
  • Produce lamellar bodies (keratin factories)
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14
Q

What is the structure of the stratum basale (innermost layer)?

A
  • Tall columnar epithelial cells
  • Constantly renew keratinocytes by cell division
  • As daughter cells differentiate they move away from the epidermis-dermis junction, make keratin filaments and lose ability to divide
  • Contains melanocytes
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15
Q

What additional layer of the epidermis is present in thick skin (e.g. palm of the hand)? Between which layers is this found?

A

Stratum lucidum

Between the stratum corneum and stratum granulosum

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16
Q

What is the normal transit time for a keratinocyte from the basal layer to the stratum corneum?

A

28-40 days

17
Q

In psoriasis the transit time of keratinocytes through the epidermis is reduced, how does the skin appear and what is the transit time for the cells?

A

Stratum corneum is produced in an abundance of silvery scales every 2-3 days

18
Q

What is hyperkeratosis?

A

Too much keratin is put on the surface of the skin, especially the hands and feet.

19
Q

What are melanocytes and what do they do?

A
  • Cells in the basal layer that produce melanin, the pigment that gives skin its colour
  • In dark skin, produce more melanin but same number of melanocytes
  • Melanocytes can donate pigment to the keratinocytes around them - keratinocytes phagocytose the tips of the dendritic processes of the melanocyte
20
Q

What are Langerhans cells in the epidermis?

A
  • Highly specialised antigen presenting cells

- Present to T lymphocytes to mediate immune reactions (e.g. allergic contact dermatitis)

21
Q

What are Merkel cells?

A
  • Mechanoreceptor cells associated with sensory nerve endings
22
Q

What are the two types of skin? What are the exceptions to the rule?

A
  • Thin (hairy) skin
  • Thick (non-hairy) skin

Exceptions: lips, back of ear, some areas of external genetalia

23
Q

Where can thick (non-hairy) skin be found? What is its function?

A
  • Palmar surface of hand, plantar surface of foot, areas between the fingers and toes
  • Prevents tissue loss from abrasion
  • Increases friction between skin and surfaces
  • Increased sensation
24
Q

How does the structure of thick (non-hairy) skin differ from thin (hairy) skin?

A
  • Thin skin has hair follicles, sebaceous glands and arrector pili muscles
  • Thick skin has more pronounced ridges and furrows on surface
  • Thick skin has more regular shaped dermal papillae
  • Thick skin often has the stratum lucidum which is absent in thin skin
25
Q

What are the three types of hair and where are they found?

A
  • Lanugo - covers the developing foetus and sometimes seen at birth
  • Vellus - short, thin, light and soft - not connected to sebaceous glands (replaces lanugo)
  • Terminal - head, axillae, external genitalia - long, wide, dark and coarse (produced by action of testosterone)
26
Q

What are the functions of hair?

A
  • Thermoregulation - arrector pili muscles contract in low temperatures or are stimulated by the sympathetic nervous system
  • Sexual attraction - apocrine sweat glands secrete pheromones (hairs trap these oils)
  • Sensation - hairs have sensory nerve endings in the bulb (sensory awareness)
  • Protection - eyelashes and nasal hair prevent entry of dust and pathogens, eyebrows reduce light and sweat entering eyes, axilla hair conducts sweat away from the body
27
Q

Where does the arrector pili muscle attach and what causes it to contract?

A

Smooth muscle fibres attached to papillary region of dermis (origin) and hair bulb (insertion)

Involuntary contraction due to sympathetic stimulation or the cold

28
Q

The end bulbs of neurones in the dermis contain …………………..

A

Thermoreceptors

29
Q

Free nerve endings in the epidermis contain ……………… which detect …………….

A

Nociceptors, pain

30
Q

What does the tacticle disc in the dermis detect?

A

Attaches to the basal layer of keratinocytes and senses touch, pressure and texture

31
Q

What does the Meissner corpuscle detect?

A

Tapping and flicker movements

32
Q

What does the Pacinian corpuscle detect?

A

Vibrations

33
Q

What does Ruffini’s corpuscle detect?

A

Joint movements and tissue stretch

34
Q

Neurones in the dermis can wrap around hairs to form a root hair plexus, what does this detect?

A

Vibrations in the hair shaft

35
Q

What is the structure of nails?

A
  • Nail plate with a nail matrix and nail bed below

- Consists solely of alpha keratin

36
Q

What are the functions of nails?

A
  • Protect the distal phalanx and surrounding soft tissues
  • Enhance precise movements of the digits using counter-pressure
  • Enhance sensitivity of fingertip
  • As a tool (e.g. pulling, cutting or scraping)
37
Q

What are the primary functions of the skin?

A
  • Protection and repair
  • Temperature regulation and excretion of waste products
  • Lubrication
  • Storage (white adipose cells)
  • Vitamin D synthesis
  • Absorption (water, oxygen, some drugs)
  • Sensation (mechanoreceptors)

Body Logistics Revision (25 decks)

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