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MD2001 Week 5 > Structure and function of skin > Flashcards

Structure and function of skin Flashcards

1
Q

What are the functions of epithelia cells?

A
  • secretion
  • absorption
  • transport in and out
  • protective barrier
  • selective barrier
  • strength and support
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2
Q

What is the epidermis?

A
  • avascular epithelium layer of skin
  • stratified squamous keratinised epithelium
  • undergoes proliferation
  • synthesises keratin for
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3
Q

What is the function of keratin?

A
  • adheres cells together

- forms a protective layer

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4
Q

How do keratins attach in epithelial cells?

A

keratin proteins inside epithelial cells attach to proteins called desmosomes on the surface

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5
Q

What is the structure of the dermis?

A
  • vascular - blood vessels, lymphatics, cutaneous nerves
  • tough (leather)
  • collagen and elastic fibres not replaced with age
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6
Q

What is the structure of the hypodermis?

A
  • superficial fascia - varies in thickness
  • blood vessels, nerves and lymphatics
  • fatty tissue - adipose tissue
  • skin ligaments, loose skin or taut skin implication in scarring and incisions
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7
Q

Wha is cell proliferation?

A

process that results in an increase in the number of cells

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8
Q

What are the dangers of burns?

A

loss of skin barrier function

  • fluid loss
  • infection
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9
Q

What are the functions of the skin?

A

> homeostasis - temp regulation, internal homeostasis (water, electrolytes), metabolic (fit D, fat store)
sensory information - sensation (pain, temp), psychosocial signals (visual, chemicals)
protection - melanin (UV), keratin (chemicals, water, mechanical), immune (organisms)

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10
Q

What are the layers of the epidermis?

A

> S. corneum - waterproof, dead cells, organised keratin layers, cornfield
S. lucidum - specialised cell death program, few nuclei
S. granulosum - keratin aggregation
S. Spinosum - keratin filaments formed, linkage via desmosomes
S. Basale - cell division

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11
Q

What does cornfield mean?

A

process by which squamous epithelial cells develop into tough protective layers or structures (such as hair, hooves) and the outer layer of skin - final stage of keratinisation

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12
Q

What is the interface of the epidermis with the dermis?

A

stratum basale

  • hemidesmosomes (junctions) anchor basal cells to basal lamina
  • dermis anchored to basal lamina by collagen VII (epidermis binds to dermis)
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13
Q

What causes dystrophic epidermolysis bullosa?

A

a mutation in collagen VII

(interface of basal lamina with dermis - causes blistering

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14
Q

What is filaggrin?

A

a protein that binds keratin fibres in epithelial cells - maintains optimal skin barrier

  • precursor profilaggrin - formed from it during terminal differentiation of epithelial cells
  • inhibits water loss
  • main component of keratohyaline granules in the S.granulosum
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15
Q

What causes most cases of eczema and other keratinisation disorders?

A

mutations such as reduced filaggrin expression (eczema)

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16
Q

What are melanocytes?

A

found in the basal layer of the epidermis

synthesis and release melanin

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17
Q

What is melanin?

A

brown pigment
synthesised and released by melanocytes
- amount varys between races and individuals
- absorbs UV-B
- prevents DNA damage to underlying cells of hypodermis

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18
Q

What are the functions of melanin?

A
  • amount varys between races and individuals
  • absorbs UV-B
  • prevents DNA damage to underlying cells of hypodermis - lower incidence of skin cancer in individuals with more melanin
19
Q

What is melanoma?

A

tumour of melanocytes (melanin forming cells)

20
Q

Where are melanocytes derived from?

A

neural crest cells that originate near the developing nervous system and spread into the embryo - mesodermal

21
Q

What are Langerhans cells?

A

antigen producing cells of the skin

  • contain Birbeck granules
  • present in all layers of epidermis - but mainly stratum spinosum
  • activated in skin but migrate tp lymph nodes
  • express langerin which helps degrade virus (such as HIV) in specialised endoscopes called Birbeck granules
22
Q

Where are Langerhans cells found?

A

in all layers of epidermis - but mainly in the stratum spinosum

23
Q

How do Langerhans cells work?

A

express lantern which degrades virus

  • in special endoscopes called Birbeck granules
  • activated in the epidermis then migrate to the lymph nodes
24
Q

What are dendritic cells?

A

antigen presenting immune cells

25
Q

What does the dermis consist of?

A

> dermo-epidermal junction - complex to prevent shearing, papillae flatten with age (skin becomes more vulnerable)
papillary dermis - fine collagen and elastic fibres, small blood vessels and nerves
reticular dermis - coarser collagen and elastic fibres, larger blood vessels and nerves

26
Q

What is the hypodermis also known as?

A

superficial fascia

27
Q

What is the structure of the hypodermis/superficial fascia?

A
  • loose connective and adipose (fat) tissue
  • varies in thickness at different parts of body
  • vascular - superficial blood vessels and lymphatics
  • cutaneous nerves
  • deepest part of hair follicles
  • eccrine and apocrine glands
28
Q

What determines the mobility of skin implicated in scarring and incisions?

A

skin ligaments in the hypodermis/ superficial fascia

29
Q

Where is vitamin D produced?

A

in the epidermis (some however believe the hypo epidermis)

30
Q

Where are sweat glands found?

A

dermis and superficial fascia

- duct opens up on to surface of skin

31
Q

Explain eccrine sweat glands?

A
  • secrete watery fluid
  • lie in dermis and superficial fascia
  • duct opens up onto surface of skin
  • controlled by sympathetic nervous system
  • important in thermoregulation
  • part of fight or flight response (fear)
32
Q

Explain apocrine sweat glands?

A
  • secrete milky secretions containing pheromones
  • found in axillae and genital region
  • open into hair follicles
33
Q

What are hair follicles?

A
  • cylindrical, epithelial structures anchored in the hypodermis
  • hair shaft grows from bulb
  • hair shaft composed of keratin
  • follicle shaft associated with sebaceous glands that open up into the follicle
  • secrete sebum to lubricate hair and adjacent
34
Q

What makes the pilosebaceous unit?

A
  • hair follicule
  • sebaceous glands
  • hair shaft
  • arrector pili
35
Q

What is the function of the arrector pili muscle?

A

contraction of smooth muscle attached to the papillary dermis and to the sheath of the follicle pulls the hair upright (goosebumps)
- controlled by the sypathetic NS

36
Q

What are mammary glands?

A

modified apocrine sweat glands

- lactation under hormonal control

37
Q

How are nails formed?

A

nail plate made from keratin rests on the nail bed

- growth from the nail root which passes deep into the dermis

38
Q

How are teeth formed?

A

enamel of the teeth develops from the epithelium, dentine, pulp and periodontal membrane is mesodermal

39
Q

Sensory receptors of pain?

A

nociceptors

- free nerve endings

40
Q

Sensory receptors of temperature?

A

separate receptors for cold and heat

- free nerve endings

41
Q

Sensory receptors of touch?

A

meissner’s corpuscles / fine touch Merkel cells

- just beneath epidermis

42
Q

Sensory receptors of pressure?

A

pacinian corpuscles

- dermis

43
Q

Sensory receptors of vibration?

A

meissner’s corpuscle and pacinian corpuscles

- dermis

MD2001 Week 5 (10 decks)

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