Structure and function of skin Flashcards

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1
Q

From what embryological layer is the skin epidermis from?

A

Ectoderm

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2
Q

From what embryological layer is the dermis formed from?

A

Mesoderm

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3
Q

From what embryological layer are melanocyte cells from?

A

The neural crest

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4
Q

What describes the growth pattern of skin?

A

Blashkos lines

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5
Q

What kind of epithelium is the epidermis?

A

Stratified squamous

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6
Q

What is the most numerous cell in the epidermis?

A

Keratinocytes

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7
Q

How long on average does it take cells to migrate through the epidermis from the basement layer?

A

28 days

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8
Q

What happens when the time for cells to migrate up through the epidermis greatly increases?

A

Psoriasis

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9
Q

What are the four layers of the epidermis (from bottom to top_

A
  1. Basal layer
  2. Prickle cells
  3. Granular layer
  4. Keratin layer
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10
Q

What layer connects the epidermis to the dermis?

A

The basal layer

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11
Q

What type of cells dominate the prickle cell layer?

A

Desmosomes

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12
Q

How does disruption of the prickle cell manifest?

A

Moist skin

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13
Q

Describe the cells of the granular layer?

A

No nuclei

Large numbers of lipid granules

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14
Q

What two proteins make up the keratin layer?

A

Keratin and filaggrin

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15
Q

Where are basal cell carcinomas derived from?

A

Hair follicle cells

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16
Q

What do melanocytes do?

A

They convert tyrosine to the melanin pigment (melanin) which is brown

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17
Q

How do melanocytes achieve this pigmentation?

A

Inside the melanocytes their are organelles called melanosomes. These absorb light and convert it into melanin granules which are then transferred to keratinocytes through dendrites. When we are in the sun this pre formed melanin spreads out into the surrounding cells to give a tan.

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18
Q

What is the purpose of a tan?

A

The melanin cap works to protect DNA is the basal cells

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19
Q

What is vitiligo?

A

An autoimmune disease in which there is a loss of melanocytes

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20
Q

What is albinism?

A

A genetic condition where there is loss of pigment production due to an enzyme deficiency.

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21
Q

What is nelsons syndrome?

A

An excess of melanins stimulating hormone being produced from the pituitary gland.

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22
Q

What do langerhans cells do?

A

The constantly scan the epidermis for microbes and present these

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23
Q

Where do langerhans cells originate from?

A

Bone marrow

24
Q

What are merkel cells?

A

Mechanoreceptors

25
Q

What is the pilosebaceous unit?

A

The epidermal component of the hair follicle and the dermal papilla.

26
Q

How does the hair become coloured?

A

Melanocytes lying above the dermal papilla

27
Q

What do arrestor pilli muscles do?

A

Contract to cause the hair to become erect

28
Q

What are the three phases of hair growth?

A
Anagen = growing
Catagen = Involuting
Telogen = resting
29
Q

Where are new hair cells formed?

A

The hair matrix

30
Q

Why, when hair grows back is it initially white?

A

Melanin cells take longer to return than hair cells.

31
Q

What are nails made of?

A

Keratin

32
Q

In the derma - epidermal junction, what cells act as ties?

A

Hemidesmosomes

33
Q

What is epidermolysis bullosa simplex?

A

A congenital problem with the dermal epidermal junction which causes newborn babies to blister on touch.

34
Q

What do fibroblasts do?

A

Secrete collagen

35
Q

What do macrophages do?

A

Scavenge and present antigens

36
Q

What do mast cells do?

A

Chemical messengers

37
Q

What three cell types do you find in the epidermis?

A

Melanocytes
Langerhans cells
Merkel cells

38
Q

What fibres does the dermis contain?

A

Collagen and elastin

39
Q

In there a blood supply to the epidermis?

A

No. Blood must diffuse across

40
Q

In the skin, what does the upper horizontal arterial plexus supply?

A

The epidermis

41
Q

What does the lower horizontal arterial plexus supply?

A

The dermis (hair root etc)

42
Q

What is a port win stain?

A

Permanent dilatation of blood vessels in the skin

43
Q

What do pacinian cells sense?

A

Pressure

44
Q

What is neurofibromatosis? How does it manifest?

A

An overgrowth of nerve endings. Brown swelling on the skin.

45
Q

What are cafe au lait spots a sign of?

A

Neurofibromatosis

46
Q

Describe sebaceous glands

A

Hormone sensitive glands the produce sebum. The open out onto the hair follicle and protect from infection

47
Q

What glands are mostly found on the face, back and chest?

A

Sebaceous

48
Q

Describe apocrine glands

A

Androgen dependant scent glands that form part of the pilosebaceous unit and so release onto the hair follicle, lubricating the hair.

49
Q

What glands are found mostly on the axillae and perineum

A

Apocrine

50
Q

What are eccrine glands

A

Glands found across the whole skin surface that allow the body to cool by expiration. They have a sympathetic cholingeric nerve supply.

51
Q

What glands are found on the whole skin surface?

A

Eccrine

52
Q

What is erythroderma

A

Redness over most of the skin

53
Q

Where are melanocytes found?

A

Dermo epidermal junction

54
Q

How do melanocytes transfer pigment to keratinocytes?

A

Dendritic processes

55
Q

What two types of collagen make up the dermis

A

type 1 and type 111 collagen

56
Q

Describe briefly the pathogenesis of acne

A

Sebum produced by the sebaceous glands pigs the pilo sebaceous unit.
Keratin and sebum build up to produce blackheads/whiteheads.
Rupture causes acute inflammation and foreign body granulomas