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PBL Flashcards

1
Q

What are the three broad functions of the skin?

A
  1. Protection
  2. Regulation
  3. Sensation
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2
Q

What can the skin protect against? (5)

A
  1. Mechanical impacts
  2. Pressure
  3. Variations in temperature
  4. Micro-organisms
  5. Radiation/chemicals
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3
Q

How is the skin involved in physiological regulation?

A
  1. Body temperature via sweat and hair
  2. Changes in peripheral circulation
  3. Fluid balance via sweat (minor role)
  4. Synthesis of vitamin D
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4
Q

How does the skin detect sensation?

A

A network of nerve cells that detect and relay changes in environment e.g. heat, cold, touch, pain

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5
Q

What are the layers of the skin?

A
  1. Epidermis
  2. Dermis
  3. Hypodermis/subcutis
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6
Q

What are the layers of the epidermis?

A
  1. Stratum basale
  2. Stratum spinosum
  3. Stratum granulosum
  4. Stratum lucidum (palm of hands and soles of feet)
  5. Stratum corneum
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7
Q

List the cell types found in the epidermis of the skin.

A
  1. Keratinocytes
  2. Melanocytes
  3. Merkel cells
  4. Langerhan cells
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8
Q

What two types of fibres are found in the dermis of the skin?

A
  1. Collagen (mainly type I)

2. Elastin

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9
Q

List some of the cells found in the dermis of the skin.

A
  1. Fibroblasts
  2. Lymphocytes
  3. Dermal dendritic cells
  4. Mast cells
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10
Q

What are the two sub layers of the dermis of the skin?

A
  1. Papillary layer

2. Reticular layer

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11
Q

What type of tissue is found in the papillary region of the dermis?

A

Areolar connective tissue

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12
Q

What structures can be found in the papillary region of the dermis?

A
  1. Capillaries

2. Meissner’s corpuscles

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13
Q

What are Meissner’s corpuscles?

A

Tactile receptors

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14
Q

What type of tissue is found in the reticular region of the dermis?

A

Dense, connective tissue containing thick bundles of collagen fibres

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15
Q

What type of tissue is the hypodermis/subcutis?

A

Connective tissue

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16
Q

What is found in the hypodermis/subcutis?

A

Mostly adipose tissue, some vasculature and sensory receptors.

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17
Q

Where are melanocytes found and what do they produce?

A

Found in stratum basale and produce melanin and tyrosinase.

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18
Q

What does tyrosinase do?

A

Converts tyrosine to melanin

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19
Q

Where in melanocytes is melanin produced?

A

Melanosome

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20
Q

State the functions of melanin.

A
  1. Protect skin and underlying tissue from UV radiation

2. Create skin colour

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21
Q

Why does increased exposure to sunlight produce a darker skin colour?

A

Enzymatic activity in the melanosome increases in response to exposure to UV radiation, hence increased melanin production, increased pigments, darker skin colour.

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22
Q

Where are keratinocytes found?

A

Throughout the epidermis as keratinised stratified squamous epithelium.

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23
Q

What is the function of keratinocytes?

A
  1. Produce keratin - protection/barrier function
  2. Produce lamellar granules - waterproof function
  3. Vitamin D production
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24
Q

Why do melanocytes have protrusions?

A

To transfer melanin granules to the keratinocytes

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25
Q

How do melanin granules protect keratinocytes from UV radiation?

A

They surround the external side of the keratinocyte nucleus.

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26
Q

Where are Merkel cells found?

A

In the epidermis, mainly in stratum basale.

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27
Q

What is the function of Merkel cells?

A

Detect sensation

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28
Q

Where are Langerhan cells found?

A
  1. Epidermis - mostly in stratum spinosum

2. Upper dermal layer

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29
Q

What is the function of Langerhan’s cells?

A
  1. Recognise foreign microbes
  2. Engulf and destroy them
  3. Antigen presentation
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30
Q

Where do Langerhan’s cells originate?

A

In bone marrow

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31
Q

Where are the epithelial stem cells of the skin found?

A

Stratum basale

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32
Q

What is the function of the epithelial stem cells?

A

Self renewal and repopulation of epidermal layers.

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33
Q

Describe the stratum corneum layer of the epidermis.

A
  1. Anuclear, no organelles
  2. Keratinised
  3. 20-30 layers
  4. Glycolipid present
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34
Q

What is the purpose of the glycolipids in the stratum corneum?

A

Help waterproof the skin and prevent water loss

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35
Q

What is a function of the stratum corneum?

A
  1. Resist friction

2. Protect other layers from physical damage

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36
Q

Describe the stratum lucidum.

A
  1. 3-5 layers
  2. Flat, dead keratinocytes
  3. Cells appear clear
  4. Thickened plasma membranes
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37
Q

Describe the stratum granulosum.

A
  1. 3-5 layers
  2. Mature keratinocytes
  3. Produce keratohyalin and lamellar granules
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38
Q

Why do keratinocytes of the stratum granulosum start to die?

A

They are moving further away from blood supply and nutrition

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39
Q

What do lamellar granules contain?

A

Water resistant glycolipids which stick cells together.

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40
Q

Describe the stratum spinosum.

A
  1. 8-10 layers
  2. Living keratinocytes
  3. Joined together by desmosomes
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41
Q

Describe the stratum basale.

A
  1. Single layer
  2. Cuboidal epithelium
  3. Sits on basement membrane
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42
Q

As cells in the stratum spinosum are alive, what structural feature is important for communication?

A

Desmosomes

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43
Q

What is the function of the stratum basale?

A

To regenerate the other layers by constant cell division

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44
Q

How does self renewal of the epidermis occur?

A
  1. Dead keratinocytes of the stratum corneum slough off
  2. Stem cells in stratum basale start to replicate and differentiate
  3. Cells move up from stratum basale to stratum corneum
  4. Process takes about 4 weeks/a month
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45
Q

Describe the keratinisation at each epidermal layer.

A
  1. Stratum basale - scattered tonofilaments
  2. Stratum spinosum - tonofibrils
  3. Stratum granulosum - keratohyalin granules
  4. Stratum corneum - keratin
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46
Q

List some functions of the dermis.

A
  1. Immune role
  2. Blood supply
  3. Tensile strength (from collagen)
  4. Allows stretch (elastin fibres)
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47
Q

List some functions of the dermis-epidermal junction.

A
  1. Attachment of epidermis to dermis (basement membrane in between)
  2. Align cells of epidermis
  3. Base for re-epithelialisation in wound healing
  4. Barrier/regulation function (into and out of epidermis)
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48
Q

List the functions of the hypodermis/subcutis.

A
  1. Energy source
  2. Shock absorption
  3. Insulation
49
Q

Where are free nerve endings of the skin usually found?

A
  1. Most in papillary layer of dermis

2. Some in epidermis where they attach to Merkel cells

50
Q

What is the function of the free nerve endings in the skin?

A

To act as mechanoreceptors

51
Q

Where are Meissner’s corpuscles usually found?

A

In the papillary dermis of hand and feet

52
Q

Where are Pacinian corpuscles usually found?

A

Hypodermis/subcutis

53
Q

What is the function of Pacinian corpuscles?

A

To detect deep pressure and vibration

54
Q

What are the adnexal structures of the skin?

A
  1. Hair
  2. Nails
  3. Glands
55
Q

How does hair grow?

A

Grows from the dermis via invaginations of the epidermis

56
Q

Which muscle is associated with hair?

A

Arrector pili

57
Q

How are the arrector pili muscles innervated?

A

Via the autonomic nervous system

58
Q

List three types of gland found in the skin.

A
  1. Eccrine glands
  2. Apocrine glands
  3. Sebaceous glands
59
Q

Where are eccrine glands found?

A
  1. Everywhere on human skin except from nail beds, lips, external auditory canal and some parts of genitalia
  2. Most abundant on palms, soles and axillae
60
Q

What is the function of of eccrine glands?

A

Temperature control glands that control sweat excretion

61
Q

Where are apocrine glands found?

A
  1. Axillae and genitals

2. Modified in breast, eyelid and ear

62
Q

What are apocrine glands?

A

Scent glands (role unclear in humans)

63
Q

Where are sebaceous glands found?

A

Everywhere except palms and soles

64
Q

What are sebaceous glands formed from?

A

Hair follicles

65
Q

What do sebaceous glands do?

A

Produce sebum to lubricate and help waterproof skin

66
Q

When do sebaceous glands enlarge?

A

In puberty in response to androgens

67
Q

What could chronic UV exposure in humans lead to? (5)

A
  1. Loss of skin elasticity/fragility
  2. Abnormal pigmentation
  3. Haemorrhage of blood vessels
  4. Wrings and premature ageing
  5. Cancer
68
Q

Why is it important that melanocytes do not completely block the effects of UV light?

A

Because UV light is needed for vitamin D synthesis

69
Q

List some of the molecules found in the epidermis. (7)

A
  1. Keratins
  2. Profilaggrin
  3. Involucrin
  4. Loricin
  5. Polysaccharides
  6. Glycoproteins
  7. Lipids
70
Q

Where are keratins found and what is their function?

A

Found: all epidermal layers
Function: structural proteins

71
Q

Where is profilaggrin found and what is its function?

A

Found: Keratohyalin granules in stratum granulosum
Function: converts to Filaggrin which aggregates keratin filaments in to tight bundles

72
Q

Where is Involucrin found and what is its function?

A

Found: keratohyalin granules in stratum granulosum
Function: formation of cell envelope around cells in stratum corneum

73
Q

Where is Loricin found and what is its function?

A

Found: keratohyalin granules in stratum granulosum
Function: cross links to Involucrin

74
Q

Where are polysaccharides, lipids and glycoproteins found in the skin and what is their function?

A

Found: lamellar granules
Function: extrude in to extracellular space, form ‘cement’ that holds together cells of stratum corneum

75
Q

What is the function of the fibroblasts found in the dermis?

A

Synthesis of collagen, elastin and other ECM components

76
Q

What is the function of the lymphocytes found in the dermis?

A

Immunosurveillance

77
Q

What is the function of the dermal dendritic cells found in the dermis?

A
  1. Phagocytosis

2. Antigen presentation

78
Q

What is the function of the mast cells found in the dermis?

A
  1. Produce inflammatory mediators e.g. histamine, heparin

2. Produce chemotactic factors for neutrophils and eosinophils

79
Q

List some of the molecules found in the dermis.

A
  1. Collagen
  2. Elastin
  3. Proteoglycans and glycosaminoglycans (hydration)
80
Q

Which layers of skin would be affected in an abrasion and erosion?

A

Epidermis only

81
Q

Which layers of skin would be affected in ulceration of the skin?

A

Structures deep to the epidermis

82
Q

Which layers of skin would be affect in a partial thickness wound?

A

Epidermis and dermis

83
Q

Which layers of skin would be affected in a full thickness wound?

A

Epidermis, dermis and deeper structures

84
Q

What are the three overlapping phases of wound healing?

A
  1. Inflammation
  2. Proliferation
  3. Remodelling
85
Q

List some of the cells that would be involved in wound healing.

A
  1. Keratinocytes
  2. Neutrophils
  3. Macrophages
  4. Fibroblasts
  5. Myofibroblasts
  6. Endothelial cells
86
Q

How long does the inflammatory phase of wound healing take?

A

24-48 hours

87
Q

Briefly describe what happens during the inflammatory phase of wound healing.

A
  1. Platelets initiate haemostasis (if vessels affected)
  2. Clot attracts other cells to wound site to fight infection
  3. Neutrophils and macrophages phagocytose dead tissue and microorganisms
88
Q

What happens during the proliferative stage of wound healing?

A
  1. Re-epithelialisation
  2. Formulation of granulation tissue
  3. Neovascularisation
89
Q

Briefly describe what happens during re-epithelialisation.

A
  1. Cell-cell adhesions loosen so cells can migrate to wound site, cover granulation tissue and meet in the middle
  2. Once wound is covered in single layer of keratinocytes all keratinocytes start to proliferate
90
Q

What type of collagen is mainly relevant in the formation of granulation tissue?

A

Collagen type III (will later be converted to type I)

91
Q

What happens during neovascularisation?

A

Proliferation and migration of endothelial cells

92
Q

What are the two methods by keratinocytes can migrate?

A
  1. Leap frog method

2. Train method

93
Q

Briefly describe what happens during the remodelling phase of wound healing.

A
  1. Granulation tissue becomes mature scar tissue
  2. Collagen is organised in to thick bundles and extensively cross linked
  3. Collagen type III switched to type I
94
Q

What is the strength of skin once the remodelling phase is complete?

A

70-80% of pre-injured skin

95
Q

What is the scar strength at 1 week, 3 week and 1 year?

A

1 week: 5%
3 weeks: 20%
1 year: 70-80%

96
Q

List some of the molecule involved in wound healing.

A
  1. Epidermal growth factor
  2. Platelet derived growth factor
  3. Vascular endothelial growth factor
  4. IL-1
  5. IL-6
  6. TNF-a
97
Q

How does EGF contribute to wound healing?

A

Through re-epithelialisation (proliferation and migration of keratinocytes)

98
Q

How does PDGF contribute to wound healing?

A
  1. Matrix formation (increased numbers and activity of fibroblasts)
  2. Remodelling (production of proteases)
99
Q

List the local factors that affect wound healing.

A
  1. Infection
  2. Foreign body
  3. Oxygenation
  4. Vascular supply
100
Q

List the systemic factors that may affect wound healing.

A
  1. Age
  2. Diseases e.g. diabetes
  3. Alcohol and smoking
  4. Obesity
  5. Immunocompromised conditions
  6. Medications e.g. glucocorticoid steroids
101
Q

What requirements must be met for consent to valid and legal? (5)

A
  1. Patient must have capacity
  2. Patient must be informed
  3. Consent must be voluntary
  4. Must not be coerced
  5. Must not be manipulated
102
Q

Where is proxy consent applicable?

A

When an adult lacks capacity.

103
Q

When is consent still lawful when the patient does not wish to know all of the relevant information regarding the proposed treatment?

A

When the risks associated with the treatment have been explained in terms that the patient can understand.

104
Q

What two factors influence whether a risk should be communicated to a patient?

A
  1. The severity of the risk

2. The importance of the risk to the patient

105
Q

Do ‘material risks’ have to be communicated even if a patient does not ask about them?

106
Q

When is it appropriate to assess a patients capacity?

A

When there are substantial reasons to doubt a presumption of capacity.

107
Q

Which act is in place for adult that lack capacity but need medical treatment?

A

Adults With Incapacity (Scotland) Act 2000

108
Q

What does a certificate of incapacity allow the medical practitioner to do?

A

To safeguard or promote the physical or mental health of the adult.

109
Q

Prior to losing capacity, who can a patient nominate to authorise decisions that will benefit them (the patient).

A

A welfare guardian

110
Q

Which act authorises treatment who lacks capacity for a mental disorder?

A

Mental Health (Care and Treatment) (Scotland) Act 2003

111
Q

In genuine emergency situations, is it lawful to authorise life saving treatment?

112
Q

When are there exceptions to providing life saving treatment for adult patients?

A
  1. When they have unambiguously specified in an advance directive that they do not wish to receive this
  2. If it is not clinically indicated
113
Q

In Scotland, when does parental responsibility apply until?

A

Until young people reach the age of 16

114
Q

Can minors have the capacity to make specific medical decisions on their own behalf depending on their level of understanding and the nature of the medical treatment?

115
Q

Which statutory provision allows young people under 16 to make certain medical decisions on their own?

A

Section 2(4) capacity from the Age of Legal Capacity (Scotland) Act 1991

116
Q

What must be assessed in order to determine whether or not a patient has capacity?

A

The patient’s ability to:

  1. Act
  2. Make reasoned decisions
  3. Communicate decisions
  4. Understand decisions
  5. Retain the memory of decisions
117
Q

Describe H&E staining.

A

Haematoxylin: basic so stains acidic structures purple/blue
Eosin: acidic so stains basic structures red/pink

118
Q

What are the four stages of tissue processing for histology?

A
  1. Fixation
  2. Embedding
  3. Sectioning
  4. Staining

Phase 1 - Week 1 (8 decks)

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