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Medicine 1 - 11 Infection and Inflammation > 04 Skin > Flashcards

04 Skin Flashcards

1
Q

Describe the functions of the skin

A

Protection from external damage
- UV light, chemical, thermal, and mechanical injury and resistance to shear stress - thick skin

Barrier
- waterproof and barrier to bacteria (sebum)

Sensation
- touch, pressure, pain, and temperature

Metabolic
- synthesises metabolic Vit D3, subcutaneous fat is a major energy store

Thermoregulation
- insulation, heat loss by sweat, evaporation, and vasodilation

Excretion
- sweat

Immune response
- inflammation, antigen presentation on cell

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2
Q

Name the layers of the skin

A
  1. Epidermis (epithelium)
  2. Dermis (connective tissue)
  3. Hypodermis/subcutis (fascia)
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3
Q

Briefly describe the structure of the skin

Layers

A

Epidermis

  • stratified squamous epithelium (Keratinised)
  • Keratinocytes (to make keratin)
  • layer of dead cells (with no nucleus)

Dermis

  • dense irregular connective tissue
  • fibroblasts, collagen I, elastin, blood, nerves, and receptors
  • Divided into the papillary and reticular dermis

Hypodermis
- adipose tissue and main blood supply

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4
Q

Name the layers in the epidermis

bottom to top

A
  • Stratum Basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum Lucidum (in thick skin only)
  • Stratum corneum
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5
Q

Describe the layers in the epidermis

A 
Stratum basale (germinativum)
- mainly contains stem cells, which divide into Keratinocytes

Stratum spinosum

  • cells have connections (spinous processes)
  • Connections have cell junctions (desmosomes), that allow for communication
  • Cells are also connected to the Stratum Basale

Stratum Granulosum
- granular layer - high amount of granules are seen

Stratum Lucidum

  • in thick skin only (soles and palm) (clear)
  • subdivision of stratum corneum

Stratum Corneum

  • in thick and thin skin
  • Uppermost layer - has mainly keratinised cells
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6
Q

Describe how and why cell turnover is important in the epidermis

A

As cells move up, they die (programmed cell death)
- They lose organelles and get filled with Keratin (protein)

Those keratinised cells then exfoliate, and new cells then produce them

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7
Q

Describe how cell turnover happens in the epidermis

A
  1. Mitosis/cell division in the basal layer
  2. Differentiation + apoptosis as cells move up
  3. Exfoliation of keratinised cells
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8
Q

Describe the barriers that are involved in the skin (in the epidermis) - that aid function

A

Tight junctions
- prevent paracellular diffusion

Desmosomes and Hemidesmosomes
- prevent mechanical and sheer forces

Keratin
- microorganism protection

Phospholipid
- waterproofing

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9
Q

Describe the dermis layer of the skin

A
  • Connective tissue
  • middle layer
  • Contains hair and gland structures

Divided into Papillary and Reticular dermis

In erectile organs (aveolar, nipples)
- below reticular leayer, there is smooth muscle, resulting in puckering of the skin

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10
Q

Describe the Papillary layer of Dermis

A

Papillary layer - superficial layer

  • type I and III collagen
  • elastic fibres (fibres are very irregular)
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11
Q

Describe the Reticular layer of the Dermis

A

Reticular Layer - Deep layer

  • mainly type I collagen
  • elastic fibres (not regular, BUT run parallel to each other, forming Langer Lines)

Langer Lines
- if wound happens parellel to Langer lines, wound healing is quicker, and a lot less scarring (you are not cutting across the fibres)

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12
Q

What is the Dermal Papillar?

A

Dermal Papillar

- protrusions of the dermis into the epidermis

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13
Q

What are epidermal ridges/Rete Ridges?

A

Epidermal Ridges/Rete Ridges

- They are protrusion of the epidermis into the dermis

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14
Q

What is the purpose of the dermal papillar and epidermal/rete ridges?

A

To increase SA

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15
Q

Describe the Hypodermis layer of the skin

A

Mainly adipose tissue
- provides insulation and a form of energy store

Also contains erector pili muscles
- pulls hair follicles to stand up (goosebumps)

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16
Q

What are the different skin cell types?

A
  • Keratinocytes (95%)
  • Melanocytes
  • Langerhans Cells
  • Merkel cells
17
Q

Describe Keratinocyte cells

A

They are:
- Stratified Squamous Keratinising epithelial cells

Keratinising: produce keratin-filled cells, loss of organelles and nucleus

They produce Keratin (hard - hair and nails, soft keratin)

18
Q

Describe the process of Keratnisation in the epidermis of the skin

(with how Keratin is made)

A

Keratin protein needs to be bundled together
- so they first form filaments (keratin filaments)
- which then further bundle together - Tonofibrils
[for the Keratin to form Tonofibrils, Keratohyalin granules needed]

Once the cells from the basal layer reach the stratum spinosum
- granules (Keratohyalin) begins to form in cells

Once they reach stratum granulosum
- high concentrations of Keratokyalin granules are present

When cells go from granulosum to corneum
- Cells have been completely Keratised

19
Q

Describe Melanocyte cells

A

Melanocytes make melanin

  • they are neural crest-derived cells in Stratum Basale
  • pigment synthesising cells responsible for skin and hair colour
  • ratio of Melanocytes:Keratinocytes is the same for all people, but the amount of melanin secreted varies

Melanosomes in the cytoplasm contain Melanin and are passed to Keratinocytes

  • leading to scattering of UV light - protecting for DNA
  • there is a higher concentration of Melanin above the nucleus, for the protection of the DNA
20
Q

Describe Langerhans cells

A

All layers and upper dermis-prominent in spinosum
- they are bone marrow-derived

They are dendritic, antigen-presenting cells

  • that migrate to regional lymph nodes
  • and communicate with the immune system (activate T cells)

Invasion of Pathogen into the epidermis

  • it must be phagocytosed
  • and present antigen on MHC Class II on the cell surface (dendritic cells)
21
Q

Describe Merkel Cells

A

They are clear cells in the Stratum Basale

  • plentiful in touch areas
  • they act as Mechoreceptors (pressure)
  • connected to keratinocytes and afferent nerves
  • Neuroendocrine function

Merkel cells connect to free nerve endings
- acting as a Mechanoreceptor

22
Q

Describe the vascular supply to the skin

A

Maintains skin nutrition

- whilst being able to alter flow to facilitate heat loss/conservation of heat

23
Q

Name some skin specialisations

A

Down-growth from the epidermis

  • Hair follicles
  • Sweat glands
  • Sebaceous glands
24
Q

Describe Hair follicles as a skin specialisation

A

Hair follicles

  • they produce hair shafts (keratin) for thermoregulation and display
  • Erector pili muscle - can pull on hair to make it sit/stand (hence, trap air for insulation, vice versa for goosebumps)
25
Q

Describe sweat glands as a skin specialisation

A

2 types:

Eccrine

  • dermal-subcut junction of all skin, produce sweat
  • The Ducts open directly onto the skin surface (thermoregulation)

Apocrine

  • localised (axilla/groin) scent production
  • open into hair follicles above the sebaceous gland
  • functional at puberty
26
Q

Describe sebaceous glands as a skin specialisation

A

The majority are associated with hair follicles

  • they secrete lipid mixture - sebum
  • into the hair follicle (for Waterproofing)

Located in the dermis and subcutis

27
Q

Describe the sensory (afferent) innervation of the skin

A 
Pacinian corpuscle (modified Schwann cells)
 > in subcutis, deep pressure + vibration

Meissner’s Corpuscle
- in the papillary dermis, rapidly adapting mechanoreceptors - light touch/pressure sensation

Ruffini Corpuscle
- mechanoreceptors, stretching of the skin

Free nerve endings

  • (pain, itch, temperature)
  • in the papillary dermis
  • when associated with Merkel cells, they are slowly adapting mechanoreceptors
28
Q

Describe the efferent (motor) nerve endings of the skin

A
  • Vessel diameter and blood flow

- Information to sweat glands and erector pili muscles

Medicine 1 - 11 Infection and Inflammation (1 decks)

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