Structure and Function of the skin Flashcards
1
Q
What is the largest organ of the body?
A
The skin (duh)
2
Q
What are the two layers of the skin?
A
Epidermis
Dermis
3
Q
What is more superficial, the epidermis or the dermis?
A
The Epidermis
4
Q
What is the epidermis made of?
A
Stratified squamous epithelium
5
Q
Embryologically, what kind of cells does the epidermis arise from?
A
Ectoderm cells
6
Q
How thick is the epidermis?
A
1.5mm
7
Q
True or False, 95% of the cells in the epidermis are melanocytes?
A
FALSE
95% are keratinocytes
8
Q
What are the four layers of the Epidermis?
A
Keratin layer
Granular layer
Prickle cell layer
Basal layer
9
Q
What other cells are found in the epidermis?
A
Melanocytes
Langerhans cells
Merkel cells
10
Q
Where is the dermis in relation to the epidermis?
A
Beneath it
11
Q
What is the dermis made of?
A
Connective tissue
12
Q
What is the dermis formed from (embryologically)?
A
Mesoderm
13
Q
How many layers are there to the foetal skin at 4 weeks?
A
3
Periderm
Basal layer
Dermis
14
Q
Name 2 Skin appendages:
A
Hair follicles
Melanocytes
15
Q
What is the function of the arrector pili?
A
Controls temperature
16
Q
What are the lines of skin development known as?
A
Blaschko’s lines
17
Q
What three factors control the regulation of epidermal turnover?
A
Growth factors
Cell death
Hormones
18
Q
How long does the regeneration of the epidermis take in healthy skin?
A
28days
19
Q
How long does the regeneration of the epidermis take in psoriasis patient’s?
A
5days
20
Q
How thick is the basal layer?
A
One cell thick
21
Q
Are there intermediate filaments in the basal layer?
A
Yes, lots of keratin
22
Q
Is the basal layer metabolically active?
A
Yes
23
Q
Why are there desmosomes in the prickle cell layer?
A
Because the cells are constantly vibrating and moving upwards so do not stay together
24
Q
What happens to the prickle cell layer in psoriasis?
A
It thickens
25
How thick is the granular layer?
2-3 cells thick
26
What to the large keratohyalin granules in the granular cell layer contain?
Filaggrin and Involucrin
27
Where is the origin of the cornified envelope?
The granular cell layer
28
What is the keratin layer made up of?
Corneocytes
29
What are the 4 different types of epidermal cells?
Keratinocytes
Melanocytes
Langerhan's cells
Merkel cells
30
Where do melanocytes come from?
Neural crest
31
Where are melanocytes found?
Basal layer and above
32
What kind of cell are melanocytes?
Pigment producting dendritic cells
33
What organelles do melanocytes contain?
Melanosomes
34
What are melanosomes responsible for?
Converting tyrosine to melanin
Eumelanin (brown or black)
Phaeomelanin (red or yellow)
35
T/F melanin absorbs light?
True
36
What stimulates the production of melanin?
UV light
| Hormones
37
Where do langerhan's cells come from?
Mesenchyme (bone marrow)
38
Where are langerhan's cells found?
Prickle cell layer
Dermis
Lymph noders
39
What type of cell are Langerhan's cells?
Antigen presenting cells
40
What type of cells are Merkel cells?
Basal cells
| Mechanoreceptors
41
Where are merkel cells found?
On the end of nerve fibres
| DIrect extension of the brain
42
T/F - Merkel cells can turn cancerous
True
Very rare
Caused by a viral infection
High mortality
43
What causes vitiligo?
Hypopigmentation of the skin caused by T cells attacking melanocytes
44
What is Nelson's syndrome and what causes it?
Bronzing of the skin due to excess ADH production from the pituitary stimulating melanin excess
45
What is the name for a tumour of the melanocyte cell line?
Malignant melanoma
46
What always accompanies a hair follicle?
Sebaceous gland
47
What is the name for the unit formed by a hair follicle and a sebaceous gland?
Pilosebaceous unit
48
What is contained in the pilosebaceous unit?
```
Epidermal component
Dermal papilla
Specialised kertains
Sebaceous gland
Hair pigmentation via melanocytes
```
49
What are the three stages of hair growth?
Anagen
Catagen
Telogen
50
What is the anagen pahse?
The growing phase
51
What is the catagen phase?
The involuting phase
52
What is the telogen phase?
The resting phase
53
What can induce the telogen phase?
Chemotherapy
| Hair loss
54
What do nails contain?
Specialised keratin
55
Where do nails orignate from?
Nail matrix
56
How fast do nails grow?
0.1mm a day
57
Which nails grow faster (toenails or fingernails)?
Fingernails
58
Where is the dermal-epidermal junction?
Interface between the epidermis and the dermis
59
What interactions does the DE junction play a key role in?
Epithelial-mesenchymal interactions
60
How is the DE junction involved in Basal cells?
Involved in support, anchorage, adhesion growth and differentiation
61
Is the DE junction permeable?
Semi-permeable
62
What are the three layers of the DE junction?
Lamina Lucida
Lamina Densa
Sub-lamina densa zone
63
What can occur when the junction is non-functioning?
Fragile skin
| Fluid filled blisters
64
What is the dermis made up of?
```
Ground substance
Cells
Fibres
Muscles
Blood vessels
Lymphatics
Nerves
```
65
What does ground substance consist of and what does it do?
Glycans, proteins and acids
| Gives the dermis structure
66
What cells are found in the dermis?
```
Mainly fibroblasts
Macrophages
Mast cells
Lymphocytes
Langerhan's cells
```
67
What fibres are found in the dermis?
Collagen
| Elastin
68
What is the pathway for the flow of blood?
Arteriole>Precapillary sphincters>Arterial>Venous capillaries>Post capillary venules> collecting venules
69
What are lymphatics?
Sub-epidermal meshed networks
Smaller non-contractile vessels drain to larger contractile lymphatic trunks
Continously drains plasma proteins, dead cells and excess interstitial fluid
70
What is neurofibromatosis?
Overgrowth of nerve endings
71
What is angioma?
Overgrowth of blood vessels
72
What are the three types of skin glands?
Sebaceous
Apocrine
Eccrine
73
What do sebaceous glands secrete?
```
Holocrine into the pilary canal
Sebum
Wax
TG
FFA
```
74
Where are sebaceous glands found?
Widely distributed
| Largest glands in the face and chest
75
What do sebaceous glands control?
Moisture loss
76
What do sebaceous glands protect from?
Fungal infection
77
Where are apocrine glands from?
Underarm
| Groin
78
What are apocrine glands dependent on?
Androgens
79
What do androgens produce?
Oily fluid and odour
80
What is the function of apocrine glands?
Unknown
81
Which glands are the most active?
Eccrine
82
Where are eccrine glands found?
Everywhere
| Specifically palms, soles and axillae
83
What is the nerve supple to the eccrine glands?
Sympathetic cholinergenic
| Mental, thermal and gustatory stimulation
84
How much fluid can eccrine glands filter?
>10L a day
85
How many eccrine glands are present in the body?
2-4 million glands
86
What is the function of eccrine glands?
Moistens palms and soled to aid grip
87
What are the main functions of the skin?
```
Barrier function
Metabolism and detoxification
Thermoregulation
Immune defence
Communication
Sensory function
```
88
What does the skin act as a barrier from?
```
Friction
Mechanical trauma
UV radiation
Chemicals
Bacterias
Viruses
Fungi
```
89
What are the consequences of skin barrier failure?
Fluid loss > Dehydration
Protein loss > Hypoalbuminaemia
Infection
90
T/F the skin is metabolically active?
True
91
How does vitamin D metabolism occur?
Cholecalciferol to Vitamin D3 occurs in the dermis
92
Where does thyroid hormone metabolism occur?
Tryroxine to Triiodothyrnine in the periopheral tissues and thyroid
93
What is the consequences of metabolism and detoxification?
Disordered thyroxine metabolsim
94
What does thermoregulation protect against?
Hot and cold
95
What are does thermoregulation control?
Sweating, shivering and blood supply
96
What is the consequence of failure of thermoregulation?
Heat loss>Hypothermia
97
What is immune defence important in?
Protection against infection
Sunlight responses
Allergic reactions to chemicals and drugs
98
What cells act in the immune defence?
Langerhans and T cells
99
What is the consequence of failure of immune defence?
Spread of infection
100
What is the skin involved in communicating?
Visual
Odour
Sociosexual behaviour
101
What does the sensory function of the skin regulate?
```
Touch
Pressure
Vibration
Pain
Itch
Heat and cold
```
