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zkin Flashcards

1
Q

What is happening to skin constantly

A

self renewing as sloughing off from surface of epidermis.

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2
Q

Layers of skin

A

Epidermis
Dermis
Subcutis/hypodermis

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3
Q

Functions of skin

A
  • Protection against water, infection and sunlight
  • Detection of sensory stimuli
  • Thermoregulation (e.g. sweat to cool)
  • Prevention of dehydration
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4
Q

What is the epidermis

A

Epidermis is outer surface layer of skin, sweat glands and hair follicles are down growths of this layer

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5
Q

Are there blood vessels in epidermis

A

No

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6
Q

What type of epithelia is epidermis

A

stratified squamous epithelium

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7
Q

Describe tough upper layer of epidermis with regards to keratin

A

tough keratinized upper layer, formed from keratin producing cells (keratinocytes) which die forming keratin plates (squames). Outermost layer of keratin constantly being shed and replaced by new keratinocytes from deeper layers

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8
Q

Describe layers of epidermis

A 
Stratum basale/basal layer
Stratum spinosum/pickle layer
Stratum granulosum/granular layer
Stratum lucidum
Stratum corneum
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9
Q

Describe Stratum basale

A
  • Cuboidal/columnar cells are attached to each other and underlying basement membrane by hemidesmosomes
  • Layer contains stem cells and daughter cells that divide to produce keratinocytes
  • basal layer contains scattered melanocytes (and hence melanin)
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10
Q

Describe stratum spinosum

A
  • Sits on basal layer
  • formed from polyhedral cells with round central nuclei.
  • High levels of keratin expression. - Intracellular bridges made of cytoplasmic projections connect these prickle cells. - Projections terminate as desmosomal junctions on cell surface between cells.
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11
Q

Describe stratum granulosum

A
  • High levels of keratin, (new synthesised reduced) cells contain many keratohyaline granules and keratinosomes
  • In upper layers, cells become flattened and densely packed, with little cytosol.
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12
Q

Role of keratohyaline granules

A

These appear dark, contain specialised linking proteins proteins that have sulphur rich amino acid (e.g. Cys) involved in crosslinking with each other and keratin tonofilaments in stratum corneum. When these cells die, release contents, permits cross linking with keratin filaments leads to cornified layer

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13
Q

What are keratin tonofilaments

A

Tonofilaments found in all layers of epidermis, they link to desmosomes in stratum, spinosum and hemidesmosomes in stratum basale.

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14
Q

What is stratum lucidum

A

Merges with upper layer of stratum granulosum, consists of flattened cells where organelle/nuclei not readily apparent

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15
Q

What is stratum corneum

A
  • tough keratinised uppermost layer, where keratin is formed from dead cells
  • Layer is constantly shed and replaced by new keratinocytes from deeper layers which die, forming keratin plates (squames).
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16
Q

Why is epidermis waterproof

A

In stratum corneum Glycophospholipids stick the dead flakes of cells together and are hydrophobic making layer waterproof

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17
Q

Describe turnover of cells from basal layer to desquamated keratin in traumatised site

A

E.g. sole of feet, quicker

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18
Q

Cornified layer much thicker in…

A

Thick skin

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19
Q

What does thickness of cornified layer influence

A

Strength of epidermis

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20
Q

Describe development of keratinocytes

A

Epidermal stem cells diff to become keratinocytes.

  • these move and become part of stratum spinosum, granulosum and then corneum (become corneocytes)
  • Corneocytes will eventually be shed off through desquamation as new ones come in
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21
Q

Describe the cell junctions found in skin

A
  • Tight junctions only occur in upper layers, so growth factors can diffuse to these apical layers.
  • Cell-cell (desmosome) and cell basement membrane (hemidesmosome) attachments necessary for structural integrity of skin.
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22
Q

What is junctional epidermolysis bullosa

A

hemidesmosome defects (due to integrin mutations) lead to skin blistering. Epidermis detaches from dermis so blister formation within the lamina lucida of the basement membrane zone

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23
Q

What is pemphigus

A

is autoimmune condition, antibodies against desmoglein formed, damage desmosome so blistering of skin and mucous membrane

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24
Q

What is Epidermolysis bullosa simplex

A

affecting the keratin genes.Therefore, there is a failure in keratinisation, which affects the integrity and the ability of the skin to resist mechanical stresses
So blisters at site of rubbing

25
Q

Describe 3 other cells in epidermis

A

Melanocytes
Langerhan’s cells
Merkel cells

26
Q

What are melanocytes

A

In basal layer they synthesise melanin in melanosomes which advance along cytoplasmic processes into cytoplasm of basal and prickle cell keratinocytes (melanin released/passed into other cells via projections so entire epidermal cell layer pigmented).

27
Q

What is melanin

A

Pigment that colours skin and reduce damage caused by UV

28
Q

What is melanoma

A

: type of cancer that affects melanocytes. The primary cause of melanoma is ultraviolet light (UV) exposure which stimulates uncontrolled melanocyte expansion.

29
Q

What happens in albinism

A

: Tyrosinase catalyses formation of melanin in both types of melanosome. Defects in this pathway lead to albinism – non pigmented hair and skin
OR
with deficiencies in the transportation of melanin granules (melanosomes are modified lysosomes ), so defects in lysosomal protein trafficking

30
Q

What are langheran’s cells

A

cells present phagocytosed antigenic material to lymphocytes. Found in all layers, especially prickle layer

31
Q

What happens to Langerhan’s cells in autoimmune skin disorder/allergy

A

cytoplasmic processes increase SA of cell membrane

- more processes found in inflamed skin

32
Q

What are Merkel cells

A

epidermal basal layer, are sensory receptors in skin which synapse with peripheral nerve endings

33
Q

How are merkel cells found/arranged

A

Found as solitary cells or grouped together to form touch receptors where they are related to hair discs.

34
Q

Describe structure of hair

A

Hair is formed of organised keratin, hair follicle and shaft are controlled by erector pili muscles that allow hair to stand on end.
Hair grows from hair follicles
Hair shaft grows from hair bulb (epidermal structure) which contains rapidly dividing epithelial cells and melanocytes and surrounds dermal papilla (dermis)

35
Q

What are hair follicles

A

Invagination of epidermal tissue extending into dermis and subcutis

36
Q

What layer structure is hair bulb

A

Epidermal structure

37
Q

Which layer is dermal papilla

A

Dermis

38
Q

What do holocrine/sebaceous glands do

A

around follicle secrete sebum – mixture of lipids , waterproofs and moisturises hair.

39
Q

True of false, hair follicle well supplies by blood vessels and nerve endings

A

True

40
Q

2 types of glands

A

Eccrine and Apocrine

41
Q

Describe distribution of eccrine and apocrine glands

A

Eccrine: Everywhere
Apocrine: breast, axillae, genital region

42
Q

Describe innervation that controls sweating

A

Cholinergic sympathetic control

43
Q

What do eccrine glands do

A

Secrete sweat - thermoregulation

44
Q

What layer of skin is eccrine gland

A

Dermis/superficial subcutis

45
Q

What do apocrine glands produce

A

Viscour milky secretion

46
Q

When are apocrine glands stimulated

A

Fight or flight

47
Q

Describe innervation of apocrine glands

A

Adrenergic sympathetic control (also sex hormones)

48
Q

Apocrine glands are downgrowths of..

A

dermis

49
Q

Describe dermis, what does it contain

A

Middle layer of skin, includes blood vessels, lymphatics, nerves and nerve endings, and epidermal appendages, embedded in a connective tissue stroma produced by fibroblasts

50
Q

2 layers of dermis

A

Upper layer/superficial loose papillary dermis

Dense reticular dermis

51
Q

Describe superficial loose papillary dermis

A

thin layer of loosely arranged collagen and elastin fibres, with capillary sized blood vessels, fine nerves and nerve endings.

52
Q

Describe dense reticular dermis

A

thicker layer containing dense bands of collagen, long thick elastic fibres running parallel to skin, and blood vessels , nerves, lymphatics supplying skin.

53
Q

Describe blood supply of skin, i.e. name 2 plexuses

A

Cutaneous and subpapillary plexus

54
Q

Where is cutaneous plexus found

A

Hypodermis/dermis junction

55
Q

Where is superficial/subpapillary plexus found

A

Upper dermis/superficial appendages

56
Q

Describe what happens to subpapillary plexus

A

Loops from superficial/subpapillary plexus extend upwards to papillary dermis to form capillaries near basement membrane of epidermis.

57
Q

How is thermoregulation achieved

A

Variations in blood flow within dermis

. Controlled by arteriovenous shunts e.g. glomus bodies (artery+vein anastomoses) within dermis

58
Q

What happens in psoriasis

A

abnormally excessive and rapid growth of the epidermal layer of the skin and scaling
Basal cell proliferation regulated by signals from dermis and epidermis. These growth factors may be upregulated in psoriasis
in premature maturation of keratinocytes and keratinocytes

59
Q

What happens in basal cell cancer

A

uncontrolled growths or lesions that arise in the skin’s basal cells, which line the deepest layer of the epidermis

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