Structure and Function Flashcards
1
Q
What epithelium forms the epidermis?
A
Stratified squamous epithelium
2
Q
What is the dermis?
A
A layer of connective tissue beneath the epidermis
3
Q
Which embryological layer forms the epidermis?
A
Ectoderm
4
Q
Which embryological layer forms the dermis?
A
Mesoderm
5
Q
Foetal skin development:
- 4 weeks
- 16 weeks
- 26 weeks
A
4 weeks - periderm, basal layer, dermis
16 weeks - keratin layer, granular layer, prickle cell layer, basal layer, dermis
26 weeks - epidermis
6
Q
Blaschko’s lines
A
Developmental growth pattern of the skin. Anything wrong with the skin at birth will follow these lines. If something runs along these lines it is a genetic error
7
Q
What does the skin consist of?
A
Epidermis, appendages, dermo-epidermal junction, dermis, sub-cutis
8
Q
Appendages
A
Nails, hair, glands, mucosae
9
Q
What forms a scar?
A
The appendages no longer being present
10
Q
Function of sebaceous gland
A
Secrete grease
11
Q
Function of erector pili muscle
A
Causes hairs to erect
12
Q
Pilosebaceous unit
A
Consists of the hair shaft, the hair follicle, the sebaceous gland and the erector pili muscle
13
Q
Which cell makes up 95% of the epidermis?
A
Keratinocytes - contain structural keratins
14
Q
Layers of the epidermis
A
Keratin layer, granular layer, prickle cell layer, basal layer
15
Q
Cells of the epidermis and where they are found
A
Keratinocytes - keratin layer
Melanocytes - basal and suprabasal layers
Langerhans cells - suprabasal layer
Merkel cells - basal layer
16
Q
Things that control the regulation of epidermal turnover
A
Growth factors, cell death, hormones
17
Q
Conditions where there is loss of control in regulation of epidermal turnover
A
Skin cancer and psoriasis
18
Q
How long does it take from keratinocytes to travel from the bottom to the top of the epidermis?
A
28 days
19
Q
How many cells thick is the basal layer?
A
One
20
Q
What shape are the cells in the basal layer?
A
Small cuboidal cells
21
Q
What is there lots of in the basal layer?
A
Intermediate filaments (keratin)
22
Q
The basal layer is highly metabolically active - true or false?
A
True
23
Q
Describe the shape of cells in the prickle layer
A
Larger polyhedral cells
24
Q
What are there lots of in the prickle cell layer?
A
Desmosomes
25
What are desmosomes?
Cell to cell contacts which allow both adhesion (to impart stability) and flexibility (so cells can move upwards)
26
How many layers of cells are there in the granular layer?
2-3 layers of flatter cells
27
What does the granular layer contain?
Large keratohyalin granules, odland bodies and a high lipid content
28
What do keratohyalin granules contain?
Structural fillagrin and involucrin proteins
29
Where is the origin of the cornified envelope?
Granular layer
30
Describe cell nuclei in the granular layer
Cell nuclei are lost
31
Where are corneocytes found?
Keratin layer
32
What are corneocytes?
Terminally differentiated keratinocytes and compose most if not all of the stratum corneum. They are 'dead' cells
33
Which layer, other than the granular layer, is part of the cornified envelope?
Keratin layer
34
Function of the keratin layer
Provides a waterproof barrier to the skin and releases lamellar granules
35
Example of disease affecting keratinocytes
Human papilloma virus of keratinocyte causes warts
36
Oral mucosa
```
Masticatory (keratinised to deal with friction/pressure)
Lining mucosa (non-keratinised)
Specialised mucosa (tongue papillae - taste)
```
37
Ocular mucosa
Lacrimal glands, eyelashes, sebaceous glands
38
When are melanocytes formed in human development?
Within the first 3 months of development
39
Where are melanocytes formed in human development?
Migrate from neural crest to epidermis
40
In what layer of skin are melanocytes formed?
Basal layer and above
41
What are melanocytes?
Pigment producing dendritic cells
42
Which organelles do melanocytes contain?
Melanosomes
43
Function of melanosomes
Convert tyrosine to melanin pigment
44
Colour of eumelanin
Brown or black
45
Colour of phaeomelanin
Red, yellow
46
What drives the conversion of tyrosine to melanin pigment?
The hormone alpha MSH - part of ACTH
47
Function of melanin
Absorbs light. It is a natural density filter
48
What are full melanosomes (melanin granules) transferred from the adjacent keratinocytes via?
Dendrites
49
Why do melanosomes form a cap over the nucleus?
To protect stem cells from DNA mutations
50
Briefly describe the following conditions:
- Vitiligo
- Albinism
- Nelson's syndrome
- Melanoma
Vitiligo - autoimmune disease disease with loss of melanocytes
Albinism - genetic partial loss of pigment production
Nelson's syndrome - melanin stimulation hormone is produced in excess by the pituitary
Melanoma - tumour of the melanocyte cell line
51
What type of cells are Langerhan's cells?
Dendritic cells
52
Where do Langerhan's cells originate?
Mesenchymal origin - bone marrow
53
Where are Langerhan's cells found?
Prickle cell level in the epidermis, dermis and lymph nodes
54
Describe Langerhan's cells in the immune system
They are antigen presenting cells. They pick up the antigen in skin and circulate to lymph nodes via lymphatic system
55
Function of Merkel cells
Detect pressure and transmit touch to the brain
56
What type of receptors are Merkel cells?
Mechanoreceptors
57
Where are Merkel cells found?
They are basal cells, found between keratinocytes and nerve fibres
58
What causes Merkel cell cancer?
Viral infection
59
True or false: Merkel cell cancer has a low mortality
False - it has a high mortality
60
Phases of growth of hair
Anagen - growing
Catagen - involuting
Telogen - resting
61
Types of hair
Lanugo (in utero), vellus, terminal
62
What makes hair?
Specialised keratins
63
What is hair pigmentation via?
Melanocytes above dermal papilla
64
What makes nails?
Specialised keratins
65
2 parts of the dermis
Papillary dermis at the top and reticular dermis
66
Dermo-epidermal junction
Interface between the epidermis and dermis
67
What makes up the dermo-epidermal junction?
Lamina lucida, lamina densa, sub-laminal densa zone
68
Key roles of dermo-epidermal junction
Key role in epithelial-mesenchymal interactions - support, anchorage, adhesion, growth and differentiation of basal cells
69
Who does bullous pemphigoid tend to affect?
The elderly
70
What does bullous pemphigoid destroy?
Part of the dermo-epidermal junction
71
What technique can show the dermo-epidermal junction?
Immunofluoresence
72
Who gets epidermolysis bullosa?
It is very rare but common in babies
73
What is epidermolysis bullosa due to?
Various abnormalities in proteins in dermo-epidermal junction
74
Ground substance in the dermis
Supportive water-base substance
75
Cells present in the dermis
Mainly fibroblast – make a lot of dermis constituents e.g. collagen and elastic fibres
Macrophages
Mast cells
Lymphocytes
76
Fibres present in the dermis
Collagen and elastin
77
Which fibre is most abundant in the dermis - collagen or elastin?
Collagen - 90% of dermis is collagen based
78
What is lost in photoageing?
Elastic fibres
79
Angioma
Dilated abnormal blood vessels in the top of the skin - genetic
80
Chronic lymphoedema
Lymphatic channels so delicate they can be damaged by infection or trauma. Very difficult to manage. Causes swelling in bodies tissues
81
Dermatomes
Somatic sensory nerves in the dermis
82
Special receptors in the dermis
Pacinian - detect pressure
| Meissners corpuscles - detect vibration
83
What do pacinian receptors look like histologically?
Look like onion rings
84
What does the autonomic nerve supply innervate in the dermis?
Blood vessels, nerves, glands and supply sweat glands
85
Neurofibromatosis
Rareish genetic condition which causes a multiple overgrowth of nerve tissues
86
Acne is a disease of what?
Pilosebaceous unit
87
Pigmentation of hair follicles
Melanocytes above dermal papilla
88
What is hair made up of?
Specialised keratins, adjacent to sebaceous gland
89
Mode of secretion of sebaceous glands
Holocrine secretion into pilary canal
90
Where are sebaceous glands present?
Face, chest, (upper back)
91
True or false: sebaceous glands are hormone sensitive
True - they are quiescent until puberty
92
What do sebaceous glands produce?
Sebum: squalene, wax esters, TG and FFA
93
Functions of sebaceous glands
Control moisture loss, protect from fungal infection
94
Where are apocrine glands found?
Axillae and perineum (and nipples)
95
What do apocrine glands develop as part of?
Pilosebaceous unit
96
Apocrine glands are ___ dependent
Apocrine
97
What do apocrine glands produce?
Oily fluid that causes odour after bacterial decomposition
98
Most common form of sweat gland
Eccrine glands
99
Where are eccrine glands found?
All over the skin surface, particularly the palms of hands and soles of feet, facial skin and axillae
100
Nerve supply to the eccrine glands
Sympathetic cholinergic
101
Types of stimulation of the eccrine glands
Mental stimulation
Thermal stimulation
Gustatory stimulation
102
Describe the shape of the structure of eccrine glands
Coiled tubular structures
103
Functions of eccrine glands
Cooling by evaporation
| Moistens palms/soles to aid grip
104
Functions of the skin
```
Protective barrier
Thermoregulation
Waterproof barrier
Metabolism and detoxification
Sensory function
Communication
```
105
Physical barrier functions of the skin
Protection against friction, mechanical trauma and UV radiation (UVA (particularly damaging), UVB)
106
Chemical barrier functions of the skin
Protection against irritants, allergens and toxins
107
Pathogen protection functions of the skin
Protect against bacteria, fungi and metabolism
108
Metabolism of which things occur in the skin?
Vitamin D and thyroid hormone
109
2 main ways of getting vitamin D
Through the skin or the diet
110
Briefly describe vitamin D metabolism
7-dehydrocholesterol → vitamin D3 by UVB
111
What percentage of thyroid hormone metabolism occurs in the thyroid gland vs peripheral tissues (incl. skin)
Thyroid gland = 20%
| Peripheral tissues = 80%
112
Immune defence is important in...
Protection against infection, sunlight responses and allergic reactions
113
Cells involved in the immune defence in the skin
Langerhans cells and T cells
114
Ways of communication through skin
Visual, odour, sociosexual behaviour
115
Sensory functions of the skin
Feel touch, vibration, pressure, pain and itch, heat and cold via nerve endings and receptors in skin
116
Consequence of failure of barrier function of the skin
Infection
117
Consequence of fluid loss by the skin
Dehydration
118
Consequence of protein loss by the skin
Hypoalbuminaemia
119
Consequence of failure of thermoregulation by the skin
Heat loss leads to hypothermia
| Heat gain leads to hyperthermia
120
Consequence of failure of immune defence of skin
Spread of infection
121
Consequence of failure of metabolic function of skin
Disordered thyroxine metabolism
122
Consequences of failure of communication function of skin
Inability to display healthy skin leading to stigma
123
Basic tissue types in the skin
Epithelium, glands, muscle, hair, adipose, connective, nervous, nails
124
Describe epidermis of palm
Thick keratin layer and undulations follow those of underlying dermis giving ridges and grooves of fingerprints
125
Describe epidermis of sole of foot
Thick keratin layer and the helical structures within this layer are terminal parts of sweat ducts
126
Muscle fibres in the skin
Smooth muscle fibres, connective tissue, nervous tissue
127
Function of smooth muscle fibres in the skin
Attached to hair follicles (arrector pili) and can pull the hair perpendicular to the skin during cold/fright (goose bumps)
Also present in the walls of blood vessels
128
Function of collagen and elastic fibres in the skin
Collagen fibres and elastic fibres are present in the dermis and provide tensile strength and elastic qualities of skin
129
What types of keratin are the following:
- Central medulla of hair
- Outer cortex of hair
Central medulla = soft keratin
| Outer cortex = hard keratin
130
What does the matrix region of hair contain?
Keratin producing cells
131
What does the papilla of the hair contain?
Multiple vascular channels
132
What are nails?
Plates filled with hard keratin
133
Where does the nail plate sit?
On the nail bed
134
What happens in the nail matrix?
Cells divide and produce hard keratin
135
What is the nail cuticle?
Extension of skin fold covering the nail root
136
Function of the hyponychium
Secures the free nail edge
