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Dermatology > Structure and function of skin > Flashcards

Structure and function of skin Flashcards

1
Q

What is the Integumentary System?

A

Consists of skin and its appendages which are hair, nails and glands

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2
Q

What are the Structures of the Integument?

A

Skin

  • epidermis
  • dermis
  • hypodermis

Hairs

Glands

Nails

Sense Organs

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3
Q

What is the Epidermis

A

The outer epithelial layer of the skin

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4
Q

What are the Epidermal Layers (deep to superficial)?

A 
Stratum Basale (basal)
Stratum Spinosum (spiny)
Stratum Granulosum (granular)
Stratum Corneum (cornified)
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5
Q

Describe the Stratum Basale (basal layer).

A
  • keratinocyte stem cells attached to dermis and constantly proliferate
  • dynamic daughter cells move “up” distally through epidermis, differentiating as they go, until they are shed from the outer surface (takes 20-50 days)
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6
Q

Describe the Stratum Spinosum (spiny layer).

A
  • keratinocyte cells held together by many desmosomes (junctions), which are visible as “spines”
  • strong bonds hold the epidermis together
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7
Q

Describe the Stratum Granulosum (granular layer).

A

1-4 cell layers, but cells are flattened, so layer is thin

Keratinocyte cells contain prominent keratohyalin granules, a precursor of the protein keratin

Cells also contain lamellar bodies (granules) containing lipids and they help with waterproofing of the skin

Cells are differentiating to form outermost layer

Lack of nuclei in these cells as they don’t need to divide

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8
Q

Describe the Stratum Corneum (cornified).

A
  • outer protective layer of epidermis
  • many cells thick
  • squamous keratinocyte cells which have lost their nuclei and are cornified (full of horny keratin from keratohyalin granules), thus tough and resistant to injury
  • non-polar lipids from lamellar bodies are now between cells for waterproof purposes
  • cells flaking off and constantly being replaced
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9
Q

Name Epidermal cells other than keratinocytes.

A 
Melanocytes (pigment)
Langerhans cells (defence)
Merkel cells (sensation)
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10
Q

What are Melanocytes?

A

synthesize melanosomes (in which melanin pigment is synthesized) and transfers them to basal keratinocytes through long dendrites

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11
Q

How do keratinocytes protect the skin from UV radiation?

A

they arrange melanin pigment on top of the nucleus, protecting the nucleus from UV radiation from the sun

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12
Q

Why are melanocyte pale cells?

A

Why are melanocyte pale cells?
because their melanin pigment tends to be transferred to other basal cells, meaning not much pigment is in the melanocyte itself

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13
Q

What are Merkel cells?

A

pale cells in the basal epidermis (like melanocytes)

touch-sensors/receptors

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14
Q

What are Langerhans cells?

A

dendritic cells which form a network and function as antigen-presenting cells (like macrophages) to protect against infection

small pale cells in the upper layers of the epidermis

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15
Q

Where is vitamin D3 produced?

A

epidermis

  • mostly in basal layer
  • also in spiny layer
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16
Q

What does vitamin D3 require to make the active vitamin?

A

UV light

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17
Q

Describe the Conflict between vitamin D production and protection from UV light.

A

Vitamin D3 needs UV light to produce active vitamin D, however we want to protect ourselves from UV light to prevent DNA damage and cancer

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18
Q

What is the Relationship between skin colour and Vitamin D production?

A

dark skinned people require more UV light to produce vitamin D because they block UV light more due to the increased melanin they have

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19
Q

What is the Dermis?

A

Dense, irregular and elastic connective tissue that forms the middle layer of the skin

20
Q

Why is the dermis dense, irregular and elastic?

A

Dense
-full of collagen fibres (made by fibroblasts)

Irregular
-collagen fibres run in all directions (not parallel)

Elastic
-elastin fibres (protein complex) providing elasticity

21
Q

What does collagen in the dermis layer provide?

A

tensile strength, hence protection against abrasion and impact

22
Q

Describe the Circulation of dermis.

A

dermis carries blood and nerve supply for epidermis, therefore it is rich in blood vessels

23
Q

Describe the Structure of dermal-epidermal border.

A

Wavy to resist shear forces (rubbing sideways)

-especially on hands (fingerprints) and feet

24
Q

What are Rete ridges?

A

epidermal ridges that appear at the dermal-epidermal border and are responsible for cementing together the two layers

25
Q

What are dermal ridges?

A

Dermal projections into the epidermis (finger-like papillae)

26
Q

What is the Effect of UV light on dermal layer?

A

damage/loss of elastic fibres, resulting in loss of elasticity
-causes wrinkles

27
Q

What is the Hypodermis?

A

the subcutaneous tissue just deep to the dermis made up of mostly adipose (fat) tissue containing:

  • glands
  • hair follicles
  • nerves and blood vessels

richly supplied with blood so the body can take up nutrition/energy from fat if it needs or it or it can lay down new fat

28
Q

What is a Hypodermic syringe?

A

put in the hypodermis for a subcutaneous injection

29
Q

What is the Function of hypodermis?

A

provides insulation, cushioning and energy storage to be able to lay down fat

30
Q

What are the Skin Glands?

A

Eccrine Sweat Glands
Apocrine Sweat Glands
Sebaceous Glands

31
Q

What are Eccrine Sweat Glands?

A

normal sweat glands which respond primarily to elevated body temperature by secreting water onto skin surface, cooling the body by evaporation

32
Q

What are Apocrine Sweat Glands?

A

secrete their products into hair follicles in the armpits and anogenital region

oily fluid in humans with an unclear function, but is the source of odour after bacterial action

function increases only after puberty

33
Q

What are Sebaceous Glands?

A

secrete oily sebum into hair follicle

conditioner for hair and skin, preventing dryness and flaking

function increases only from around puberty

34
Q

What is the Muscle attached to each hair follicle?

A

Arrector pili muscle

35
Q

What does each strand of hair consist of?

A

Composed of the shaft, root and bulb that sits ina pouch like structure called the hair follicle

36
Q

What is the hair follicle?

A

epidermal tissue that dips down into the dermis, and interacts with other structures

37
Q

What does the bulb of the hair contain?

A

The hair matrix which is the active site of hair growth and pigmentation

38
Q

What ell types does the hair matrix contain?

A

2 different cell types: follicular keratinocytes and melanocytes

39
Q

What is the function of keratinocytes?

A

Filled with hard keratin which is slowly pushed up the follicle resulting in root and shaft formation

40
Q

What causes baldness?

A

The keratinocytes at the bulb of the hair only replicate a set number of times after which the hair follicle stops growing and the hair falls out

41
Q

What causes whit hair?

A

Over time melinocytes stop producing melanin

42
Q

What is the nail matrix?

A

responsible for nail growth

43
Q

What is the nail plate?

A

hard part of the nail made of keratin

44
Q

What is the Hyponychium?

A

The slightly thickened layer of skin that lies beneath the free edge of the nail plate.

Site of infection sometimes

45
Q

What are the Sense Organs in the Skin?

A
  • Thermoreceptors (in dermis): to sense heat or cold
  • Meissner’s corpuscle (in dermal papilla): multicellular structure which sense touch or vibration (Merkel cells in basal epidermis can also sense light touch)
  • Nociceptors (in dermis): sense pain (free nerve endings)
  • Pacinian corpuscle (in hypodermis): senses pressure
46
Q

What are the main skin functions?

A

Barrier/Protection, against:

· Dehydration

> Epidermis: keratin holds water, lipids stop it evaporating

· Infection

> Epidermis: forms tight impervious barrier, also immune system

· Injury/Abrasion

> All layers; epidermis is strong, rapid healing, and gets thicker where friction occurs. Dermis has collagen- tough and leathery. Hypodermis provides cushioning.

· Solar Radiation

> Epidermis: stratum corneum can absorb some UV light and melanin pigment in basal epidermal layer

Thermoregulation

· Hypodermis (insulation) keeps us warm

· Thermoreceptors tell us how warm we actually are

· Blood supply regulation

· Sweating which cools us down

Sensation

· Nerve supply and various receptors

Repair

· Epidermis- normal proliferation of cells

· Dermis- fibroblasts fill gaps with new collagen that epidermis can attach to

Vitamin D3 Production

· Epidermis

Dermatology (2 decks)

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