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The Skin Flashcards

1
Q

What is the heaviest single organ of the body and what percentage of the total body weight does it constitute for?

A

The skin makes up 16% of the total body weight

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2
Q

What are the four major functions of the skin?

A
  1. Protection
  2. Sensation
  3. Thermoregulation
  4. Metabolic functions
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3
Q

What does the skin protect against?

A

Against UV, mechanical and chemical insults, microorganisms and dehydration

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4
Q

How does the skin play a thermoregulatory role?

A

Due to the hair and deep fatty tissue

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5
Q

What metabolic functions does the skin play?

A

Tryglycerides (fat) stored within deep tissue and vitamin D is synthesised in this organ

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6
Q

What are the four layers of the skin?

A
  1. Epidermis
  2. Basement membrane
  3. Dermis
  4. Subcutis (hypodermis)
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7
Q

Does the epidermis layer of the skin have blood vessels?

A

No, it is avascular - nourished by diffusion from the dermis

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8
Q

List four types of cells present in the epidermal layer of the skin

A

Keratinocytes, melanocytes, Langerhans cells, Merkel cells

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9
Q

What is the main constituent in terms of cells of the epidermal layer of the skin?

A

Keratinocytes which make up around 95% of the epidermis

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10
Q

What are rete ridges?

A

They are epidermal thickenings that extend downward between dermal papillae

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11
Q

What is the basement membrane in the skin?

A

The multilayered structure forming the dermoepidermal junction

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12
Q

What is the dermis layer of the skin?

A

The area of supportive connective tissue between the epidermis and the underlying subcutis (hypodermis)

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13
Q

List six structures the dermis layer of the skin contains

A
  1. sweat glands
  2. hair roots
  3. Nervous cells
  4. Fibres
  5. Blood
  6. Lymph vessels
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14
Q

What is the subcutis (hypodermis)?

A

The layer of loose connective tissue and fat beneath the dermis

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15
Q

What type of epithelium cell makes up the epidermis layer of the skin?

A

Keratinising stratified squamous epithelium

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16
Q

What is the function of the keratinising stratified squamous epithelium cells that make up the epidermis layer of the skin?

A

To withstand abrasion and desiccation due to tough non-living surface layer composed of protein keratin wrapped in plasma membrane

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17
Q

As the keratinising stratified squamous epithelium making up the epidermis layer of the skin matures, what happens to the individual cells?

A

Their nucleus is eventually lost

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18
Q

How many layers of the epidermal layer of the skin can be identified easily?

A

Four layers

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19
Q

What are the four layers of the epidermal layer of the skin that can be identified easily. Start listing from the top.

A
  1. Stratum corneum
  2. Stratum granulosum
  3. Stratum spinosum
  4. Stratum basale
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20
Q

What is the cell layer in the epidermal layer of the skin which is hardly seen in microscopy except possibly in the tissue from the soles of feet?

A

Stratum lucidum

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21
Q

What is the stratum corneum?

A

The outermost layer of the skin consisting of keratinised cells

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22
Q

What is the stratum lucidum?

A

The stratum lucidum (Latin for “clear layer”) is a thin, clear layer of dead skin cells in the epidermis named for its translucent appearance under a microscope. It is readily visible by light microscopy only in areas of thick skin, which are found on the palms of the hands and the soles of the feet.

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23
Q

What is the stratum granulosum?

A

The stratum granulosum (or granular layer) is a thin layer of cells in the epidermis. Keratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer.

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24
Q

What is the stratum spinosum?

A

The stratum spinosum (or spinous layer/prickle cell layer) is a layer of the epidermis found between the stratum granulosum and stratum basale.

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25
What is the stratum basale layer in the epidermal layer of the skin?
The stratum basale (basal layer, sometimes referred to as stratum germinativum) is the deepest layer of the five epidermis layers, which is the outer covering of skin in mammals.
26
Describe what the stratum corneum layer would look like under a microscope
15-20 layers of flattened non-nucleated keratin material
27
Describe what the stratum granulosum layer would look like under a microscope
Coarse basophilic keratohyaline granules
28
Describe what the stratum spinosum would look like under a microscope
Large pale nuclei, prominent nucleoli. Intercellular bridges or tonofilaments seen
29
What type of division occurs in the stratum basale that results in regeneration and how often does the human epidermis renew?
Mitotic division leads to regeneration and human epidermis renews every 15-30 days
30
What type of cell represents a transition from the stratum granulosum and stratum corneum and is not usually seen in thin epidermis?
The stratum lucidum
31
What is the Malphigian layer?
The stratum spinosum and stratum granulosum together are sometimes referred to as the Malphigian layer
32
What is a bullous disease?
Involving blisters
33
What attaches cells to other cells (junctions) and cells to the basement?
Desosomes - molecular complexes
34
What is pemphigus?
A disease where watery blisters form on the skin
35
How does pemphigus arise?
Due to autoantibodies which bind to specific proteins such as DSG-3 and DSG-1 in the epidermis prevents the layers from adhering, causing blisters
36
What does an autoantibody against DSG3 cause?
Pemphigus vulgaris
37
What type of blisters does anti-dsg3 cause?
Deep blisters as it affects just above the basal layer
38
What does an autoantibody against DSG1 cause?
Pemphigus foliaceous
39
What type of blisters does anti-dsg1 cause?
Superficial as it is higher in the epidermis
40
What antibodies are present in bullous pemphigoid?
Antibodies to hemidesmosome proteins causing sub-epidermal blisters - lift entire epidermis of dermis
41
Describe the disease epidermolysis bullosa
Group of inherited disorders resulting from mutation in collagen 7 - anchoring fibrils attaching epidermis to dermis
42
List three cell types of the epidermis
1. melanocytes 2. langerhans cells 3. merkels cells
43
What cell type produce melanin?
Melanocytes
44
What are the melanocytes responsible for?
Skin pigmentation
45
What differs in the melanocytes of white and dark skinned people?
Little difference in number but more synthetically active in dark skinned people
46
What are melanocytes characterised by?
Dendritic processes which stretch between relatively large numbers of keratinocytes
47
Where does the melanin that has accumulated in melanosomes transfer to?
To adjacent keratinocytes where they remain as granules
48
Melanin provides protection against...
UV radiation
49
What diminshes the melanocyte population?
Ageing
50
Describe what langerhans generally look like and where they are mainly present.
They are star-shaped cells found in the stratum spinosum layer of the epidermis
51
What is special about langerhan cells in terms of what they present on the surface?
They are antigen presenting cells
52
Which cells are irregular with a lobulated nuclei, a clear cytoplasm and can only be seen with an antibody in order to ensure they are highlighter?
Langerhans cells
53
What are merkel cells?
Nervous cells - touch receptors
54
There are four epidermal skin appendages, list them
Hair follices sebaceous glands eccrine sweat glands apocrine glands
55
What do hair follicles do?
Produce hair shafts composed mainly of keratin
56
What do sebaceous glands do?
Secrete sebum which provides waterproofing
57
What are apocrine glands and where are they found?
mainly in the axilla and groin - in animals used as a scent for marking territory
58
The hair follicle is found close to what structure?
Sebaceous glands
59
What does a hair bulb look like under a microscope?
A bulbous expansion
60
What does the basal layer of germinative cells in the hair bulb contain?
Melanocytes which gives the hair its colour
61
Sebaceous cells are packed with...
lipid filled vacuoles
62
What type of glands are sebaceous glands?
Branched acinar glands
63
Where are sebaceous glands not found?
In the palms of hands or soles of feet
64
What do sebaceous glands produce?
Sebum - oily waxy substance and debris of producing cells
65
What is a holocrine gland?
Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen.
66
Why do sebaceous glands come up almost pale in microscopic images?
Because the sebum is oil. Oil is fat. Fat leaches out in tissue staining.
67
Where are eccrine sweat glands found?
Everythwere in the skin
68
Where is the main secretory component of the eccrine sweat gland located?
deep in the dermis
69
Where are apocrine glands found?
Mainly confined to areolae of breast, axillae and genital regions
70
What sort of structure do apocrine glands have?
Coiled so easily recognised
71
The apocrine cells have a what colour cytoplasm?
Pink so easily recognised
72
What does the dermis layer of the skin do?
Supports the epidermis and connects it to the hypodermis
73
Why is the surface of the dermis irregular?
Because of the dermal papillae present
74
What type of tissue does the dermis contain?
Loose connective tissue
75
What type of fibrils attach the dermis to the epidermis?
Anchoring fibrils
76
What types of cells and structures are seen in the dermal layer of the skin
Fibroblasts, mast cells, macrophages, leukocytes, blood vessels, nerve ending, eccrine/apocrine glands

Tissue Biology (16 decks)

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