The Structure and Function of the Skin Flashcards
1
Q
Where is the epidermis?
A
The outer layer
2
Q
Describe the epidermis
A
Stratified cellular epithelium
3
Q
Where is the dermis?
A
Beneath the epidermis
4
Q
Describe the dermis
A
Connective tissue
5
Q
Where does the epidermis come from and how does it form?
A
Ectoderm cells form a single layer periderm. This gradually increases in layers of cells and the periderm cells cast off
6
Q
How is the dermis formed?
A
From mesoderm below ectoderm
7
Q
What are melanocytes
A
Pigment producing cells
8
Q
Where do melanocytes migrate from
A
The neural crest
9
Q
What 5 things does the skin consist of?
A
Epidermis Appendages Dermo-epidermal junction Dermis Sub-cutis
10
Q
Give 4 examples of Appendages
A
Nails
Hair
Glands
Mucosae
11
Q
What is the majority of the epidermis made up of and what does it contain?
A
keratinocytes. It contains structural keratins
12
Q
What are the 4 types of epidermal cell layers
A
Keratin
Granular
Prickle cell
Basal
13
Q
How is the regulation of epidermal turnover controlled
A
Growth factors
Cell death
Hormones
14
Q
In what two scenarios is there a loss of control in the epidermal turnover
A
Skin Cancer
Psoriasis
15
Q
Histologically, what happens to the cells in psoriasis
A
They migrate
16
Q
Where do keratinocytes migrate from?
A
The basement membrane
17
Q
How thick is the basal layer
A
One cell thick
18
Q
What type of cell makes up the basal layer
A
Small cuboidal
19
Q
What is the main feature of the basal layer
A
It is highly metabolically active
20
Q
What are there lots of in the prickle cell layer
A
desmosomes (connections)
21
Q
What connects to desmosomes
A
Intermediate filaments
22
Q
What is the granular layer made up of
A
2-3 layers of flatter cells
High lipid content
23
Q
What is unusual about the cells in the granular layer
A
Cell nuclei are lost
24
Q
What is the main function of the keratin layer
A
To provide a tight waterproof barrier to keep you from losing water
25
What common skin disease affects keratinocytes and what does it cause?
HPV - causes warts
26
Where are the mucosal membranes in the body
```
Eyes
Mouth
Nose
Genito-urinary tract
Gi tract
```
27
What are the 3 other types of epidermal cells
```
Melanocytes (basal & suprabasal)
Langerhans cells (suprabasal)
Merkel cells (basal)
```
28
At what stage do melanocytes migrate from the epidermis to the neural crest
In the first 3 months of foetal development
29
What are the organelles called that melanocytes contain
Melanosomes
30
What is the function of melanocytes
To convert tyrosine to melanin
31
What absorbs light
Melanin
32
How are melanosomes transferred to adjacent keratinocyte
Via dendrites
33
What do melanin caps protect?
The nuclear DNA in basal cells
34
What represents an autoimmune disease with loss of melanocytes
Vitiligo
35
What happens in Albinism
A genetic partial loss of pigment production
36
What happens in Nelson's syndrome
Melanin stimulating hormone is produced in excess by the pituitary
37
What is the function of Langerhans cells
Involved in the skin immune system
38
What is the appearance of Birbeck granules
Racket organelles
39
Where are Merkel cells found
Between keratinocytes and nerve fibres
40
What do Merkel cells act as
Mechanoreceptors
41
Describe Merkel cell cancer
Rare
Caused by viral infection
High mortality
42
What is there always next to a hair follicle
Adjacent sebaceous gland
43
What are the 3 phases of hair follicle growth
Anagen (growing)
Catagen (involuting)
Telogen (resting)
44
Describe Alopecia areata
Autoimmune hair loss
45
What 3 sections make up the nail plate
Ventral
Intermediate
Dorsal
46
What is the Dermo-epidermal Junction
The interface between epidermis and dermis
47
What does the dermo-epidermal junction play a key role in
Epithelial mesenchymal interactions
Support, anchorage, adhesion, growth and differentiation of epidermal cells
Semi-permeable membrane acting as barrier and filter
48
What are present in the dermo-epidermal junction
Lots of proteins, fibrils and keratins
49
What is an inherited disease of the DEJ?
Epidermolysis bullosa
50
What is an acquired disease of the DEJ
Pemphigus, pemphigoid, dermatitis herpetiformis
51
What is the difference between inherited and acquired diseases of the DEJ
Inherited is due to a mutation in one of the proteins in the DEJ
Axquired is due to auto-antibodies to proteins in DEJ
52
Describe Epidermolysis Bullosa dystrophica
Deformity of the hands and feet - the skin fuses as it tries to over heal causing fingers and toes to stick together
53
At what age does Bullous Pemphigoid occur
Any age
54
What are the two fibres found in the dermis
Collagen and Elastin
55
Name 5 cells found in the dermis
```
fibroblasts
Macrophages
Mast cells
Lymphocytes
Langerhans cells
```
56
Name the 5 components of the dermis
```
Cells (fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells)
Fibres (collagen and elastin)
Ground substance
Vessels
nerves
```
57
What do macrophages do?
Hunt for antigen presentation
58
What do lymphocytes do
Control immune reactions
59
What are 2 risk factors for photoaging
UV light and smoking
60
What happens to the collagen in photoaging?
Collagen gets depleted
61
Describe the blood supply in the skin
Greater than metabolic needs
62
What happens in photoaging
Collagen gets depleted
63
How is Bullous Pemphigoid controlled
With the use of steroids
64
Name the 5 components of the dermis
```
Cells (fibroblasts, macrophages, mast cells, lymphocytes, Langerhans cells)
Fibres (collagen and elastin)
Ground substance
Vessels
nerves
```
65
What is the main protein in the dermis
Collagen
66
What is the function of the fibroblasts
To secrete collagen
67
What is the function of macrophages
scavengers, antigen presentation
68
What is the function of mast cells
Chemical messengers
69
What 2 factors lead to photoaging
UV lights and smoking
70
What happens in photoaging
Collagen gets depleted
71
Are blocked lymphatics easy or difficult to treat?
Difficult
72
Describe the deep vascular plexus
It is horizontal
73
What is the term given to the overgrowth of the blood vessel population
Angioma
74
Where are angiomas often found
The face
75
What are angiomas associated with?
Epilepsy
76
What is seen histologically in an angioma
Dilated vascular spaces
77
What happens if there is no protein in the blood supply
You get oedema
78
What can cause infection in the lower leg
Blockage in the lymphatics
79
Are blocked lymphatics easy or difficult to treat?
Difficult
80
What are the 2 types of special receptors in the nerves of the skin and what do they do?
Pacinian (pressure)
| Meissners (vibration)
81
What nervous system supplies the skin
The autonomic
82
Where are sebaceious glands found
Everywhere but the palms of the hands and soles of the feet
83
What is required for sweat glands to work
Motor nerve
84
Where are neurofibromatosis often found
Back, spine and brain
85
What is neurofibromatosis
Overgrowth of the nerve endings
86
What are the 3 types of skin glands
Eccrine
Sebaceous
Apocrine
87
What type of gland works to cool you down
Ecrine (sweat)
88
Over activity of which type of gland results in acne
Sebaceous
89
What are apocrine sweat glands dependent on
Androgen
90
Where are sebaceious glands found
Everywhere but the palms of the hands and soles of the feet
91
What are the functions of eccrine glands (3)
Cooling by evaporation
| Moisten palms/ soles to aid grip
92
What are the main two functions of sebaceous glands
Control moisture loss and protect from bacterial and fungal infections
93
What is the main target of the treatment of acne
To target the oil gland to stop it secreting as much
94
When does odour occur from sweat
After bacterial decomposition
95
How do apocrine sweat glands develop
As part of pilosebaceous unit
96
Where are apocrine sweat glands located
Axillae and perineum
97
What are apocrine sweat glands dependent on
Androgen
98
What occurs in cumulative irritant hand dematitis
Extra fluid between epidermal cells which can be seen between vesicle cells
99
What are the functions of eccrine glands (3)
Cooling by evaporation
| Moisten palms/ soles to aid grip
100
What are the 6 main functions of the skin
```
Barrier
Metabolism and detoxification
thermoregulation
immune defence
communication
sensory functions
```
101
What is Erythroderma largely made up of
Keratin loss or general protein loss (very dry appearance)
102
If the barrier is broken down, what happens
Dehydration
Hypoalbuminaemia
Infection
103
What is the 2 way barrier of the skin
Epidermis
104
What is the underlying cause of ichthyosis
Cholesterol not being properly metabolised
105
What can induce ichthyosis
Statins
106
What occurs in cumulative irritant hand dematitis
Extra fluid between epidermal cells which can be seen between vesicle cells
107
What happens in frostbite
There is so much vasocontstriction that the person has lost tissue
108
Describe the relationship between the wavelength of light and the depth of penetration into skin tissue
The longer the wavelength the deeper the penetration - more chance of skin cancer with deeper penetration as it can cause more damage
109
What does melanin do
Absorbs UV rays to protect DNA in the cells' nuclei
110
In which 3 ways is the skin metabolically active
Vitamin D metabolism
Thyroid hormone metabolism
Defence against chemicals, drugs, pollutatnts and sunlight
111
What is another name for crusted scabies
Norwegian scabies
112
Where does the conversion of Thyroxine T4 to Triiodothyronine T3 occur
Mostly (80%) in periphera (to thyroid)l tissues including skin and 20% in the thyroid
113
What does thermoregulation do
Protect against being too hot or too cold by controlling sweating, shivering and blood supply
114
What amount of sweat can be produced by 1 person in a day
20L
115
What happens in frostbite
There is so much vasocontstriction that the person has lost tissue
116
What are the 2 most important cells in the immune defence in the skin
Langerhans' and T cells
117
What are examples of non-specific immune defence responses
Itch, localised prickling
118
What are specific responses in immune defence
Memory response to some infection that you have previously been exposed to
119
What is another name for crusted scabies
Norwegian scabies
120
What is chronic discoid lupus erythematosus
An autoimmune disease which is caused by an inappropriate immune response
121
Name some types of sensory functions of the skin
Touch, pressure, vibration
Pain and itch
heat and cold
nerve endings and receptors in the skin
122
What condition is often associated with diabetes mellitus
Neuropathic ulcer (leprosy)
