Skin IA%% COPY XXXXXXXXXXXXX Flashcards Preview

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Flashcards in Skin IA%% COPY XXXXXXXXXXXXX Deck (17):
1

Skin as an Organ

•Combination of the 4 primary tissues: epithelium, connective tissue, muscle, nerve.

•Epidermal cells are termed keratinocytes

Largest organ in the body

•Provides  important external evidence of underlying systemic conditions: eg. liver disease, systemic sclerosis, mitral stenosis, urticaria.

•Own nerve and blood supply

 

2

Epidermis

Outer layer of skin (consisting itself of 5 strata = layers)

•Epithelial = Stratified squamous keratinising epithelium

Ectodermal origin

•Prevents water loss by evaporation

 

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3

2 layers: Structure 

1.Epidermis

- Epithelium

- Forms boundary between internal and external compartments

2.Dermis

- Connective tissue

- Gives structural strength

 Hypodermis

-  Adipose (fatty) CT layer beneath skin = subcutaneous tissue, anchors skin to underlying structures - not part of skin

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4

4 types of epidermal cells

Keratinocytes:

  • Most frequent, contain keratin (contains sulphur), hard and  resistance to abrasion.
  •  Extrude (force out) lipids – waterproofing.
  • Constantly dividing 

Melanocytes:

  • pigment formation

Langerhans cells:

  • immune surveillance

Merkel cells:

  • touch receptors

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5

Epidermal layers

•Stratified squamous keratinising epithelium

•5 layers  formed by maturing keratinocytes

•Continuum from basement membrane to skin surface

•Layers not sharply defined

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6

Epidermal layers 2 

Stratum basale (germinativum):

  • Tall columnar cells interspersed with melanocytes and Merkel cells.
  • Continuous cell proliferation - are stem cells.

Stratum spinosum:Spinous layer and Preparative layer for keratinisation.

Stratum granulosum- Presence of granules defines the layer

Stratum corneum-

 

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7

Keratinisation

  • Organic process whereby keratin is deposited in cells and these become horny as in dead skin, nails, hair.
  • Palms of hands & soles of foot - thick skin

    •Abdominal skin - thin skin

    •Dynamic - responsive to activities

    •Stratum corneum varies most

    •Dermis also varies

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8

Dermis:2 layers

Papillary layer

Loose connective tissue

–Cellular

Reticular layer

–Dense irregular connective tissue

Fibrous

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9

Dermis: papillary layer

–Loose connective tissue

–Irregular interface with epidermis - “papillae”

Cellular eg macrophages

Protective against pathogens

–Blood vessels: Thermoregulation, Nutrition

–Nerve endings: Sense organ

10

Dermis: Reticular layer

Dense irregular connective tissue

Collagen bundles in 3 planes

Elastic fibres

–Loss of elasticity is normal in old age

 

11

Skin- sense

Meissner’s corpuscles - light touch - fingertips

Paccinian corpuscles - vibration & pressure

•Pain receptors

•Thermoreceptors

12

Skin colour

•Blood

Carotene

Melanin –Protects against UV

•Melanocytes

 

13

Features

Waterproofing

  • Function of epidermis
  • Keratin in cells “waterproof
  • Keratin originates as lamellated granules in str. granulosum

UV 

  • Melanin –Protects against UV

Hair

•Thermoregulatory but not in humans

•Responsive to cold but not effective

•Practical use in skin repair

•Derived from epithelial layer

 

 

14

Origin of hair follicles

•From epidermis in utero

•Downgrowth of epithelial cells

•Invasion of knot of blood vessels

•Growth of hair

•Continuity with layers of epidermis

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15

Nails

The distal end of each digit is protected by a strong plate of hard keratin, called a nail or nail plate, which grows out from a nail bed. The nail bed, is a specialised form of skin epithelium, and has the same four layers of the epidermis of skin, with the nail plate being analogous to the stratum corneum layer.

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16

Skin glands

•Sebaceous

–Hair follicles

–Sebum

•Apocrine sweat glands

–Axilla

–Protein rich - B.O.!

•Eccrine

-Sweat

17

Thermoregulation

1.Sweat glands

2.Blood vessel dilation

–Absorption

–Radiation

3.Hair

–Polar bears not humans