The Structure of the Skin Flashcards
1
Q
What kind of epithelium is the epidermis?
A
Stratified cellular epithelium
2
Q
Describe the foetal development of the skin?
A
Ectoderm cells form single layer periderm, gradual increase in the layers of cells, periderm casts off
3
Q
What is the dermis formed from?
A
Mesoderm below ectoderm
4
Q
What is present at 4 weeks foetal skin development?
A
PBD
Periderm
Basal layer
Dermis
5
Q
What is present at 16 weeks of foetal skin development?
A
KGPBD Keratin Layer Granular Layer Prickle Cell layer Basal Layer Dermis
6
Q
What is present at 26 weeks foetal skin development?
A
Skin and all appendages
7
Q
What are Blaschko’s lines?
A
Developmental growth pattern of the skin, not following vessels, nerves or lymphatics
8
Q
What do blaschko’s lines tell you?
A
Developmental problems of the skins
9
Q
What are the skin appendages?
A
Nails
Hair
Glands
Mucosae
10
Q
Describe the demis
A
Connective tissue, less cellular, situated on a rolling sheet of fatty subcutaneous tissue
11
Q
Where does the skin permanently divide?
A
Epidermal cell layer
12
Q
Describe the skin of the hand
A
Dynamic- formation of calluses
13
Q
Describe the skin of the abdomen
A
Thin epidermis Lots of dermis Hair follicles Glands Subcutaenous fat
14
Q
Describe the skin of the scalp
A
Hair follicles and sebaceous glands
Errector pilli muscles
15
Q
What controls the regulation of epidermal turnover?
A
Growth Factors
Cell Death
Hormones
16
Q
What conditions show a loss of control of epidermal turnover?
A
Psoriasis
Skin cancer
17
Q
Why does skin appear white in psoriasis?
A
Thickened keratin does not slough off
18
Q
Why does skin appear red in psoriasis?
A
Variations in the skin thickness, blood vessels go al the way to the top of the skin
19
Q
How long does it take for a cell to travel from the basement membrane to the top?
A
28 days
20
Q
How thick is the basal layer?
A
One cell thick
21
Q
Describe the cells of the basal layer
A
Small and cuboidal
22
Q
What is found in abundance in the basal layer?
A
Intermediate filaments (keratin)
23
Q
What is the function of the basal layer?
A
Highly metabolically active
24
Q
Describe the cells of the Prickle Cell layer
A
Larger polyhedral cells
25
What is found in abundance in the prickle cell layer?
Desmosomes
26
What is the function of desmosomes in the prickle cell layer?
Connected by intermediate filaments, connect and disconnect to organise cells on their way up
27
How thick is the granular layer?
2-3 layers of flatter cells
28
What is found in the granular layer?
- Large keratohyalin granules containing structural filaggrin and involucrin proteins
- Odland bodies (lamellar bodies)
29
What is the granular layer the origin of?
Cornified envelope
30
What is the important processes of the granular layer?
Nuclei are lost, and cells filled to the brim with proteins.
The cells then burst and the granules are released, chopped open, lipids and proteins kit together and form a cornified envolope
31
What does the keratin layer consist of?
Corneocytes; overlapping non-nucleated cell remnants
| 80% keratin and filaggrin
32
What is the promise of lamellar granules in the keratin layer?
Release lipid
33
How does the skin maintain its waterproof barrier?
Tiny amino acids bind water molecules and retain water in the skin if you dont have filaggrin you get dry skin
34
What is HPV?
Infection of keratinocytes which causes warts
35
Describe the masticatory mucosa
Keratinised to deal with friction/pressure
36
Describe the lining mucosa
non-keratinised
37
Describe the specialised mucosa
tongue papillar- taste
38
Describe the ocular mucosa
lacrimal glands, eye lasher, sebaceous glands
39
What is 95% of the epidermis?
Keratinocytes
40
Describe the migration of melanocytes
Migrate from neural crest to the epidermis in the first 3 months of foetal development
41
What are melanocytes
Pigment producing dendritic cells
42
What do melanocytes do?
convert tyrosine to melanin
- eumelanin (brown or black)
- phaeomelanin (red, yellow)
43
What is the protective function of the melanocytes?
Melanosomes form a protective cap over the nucleus, protecting the nuclear DNA in basal cells
44
What stimulates melanin production?
Signal given out by the pineal gland
45
Describe vitiligo?
Melanocytes are attacked by T cells
46
What happens in albinism?
Genetic partial loss of pigment production
47
What happens in nelsons syndrome?
Melanin stimulation hormone is produced in excess by the pituitary
48
What is malignant melanoma?
Tumour of the melanocyte cell line
49
What are langerhans cells?
Suprabasal cells of mesenchymal origin.
| Found in the prickle cell layer.
50
What is the roll of langerhans cells?
Antigen presenting cells
| Pick up antigens in skin and circulate to lymph nodes
51
What is a birbeck granule?
Specific to langerhans cells, don't know what they do. Look like maracas
52
What is a Merkel cell?
Basal cell between keratinocytes and nerve fibres
53
What is the function of merkel cells?
Mechnoreceptors, direct extension of the brain
54
What is a pilosebaceous unit?
Epidermal component plus dermal papilla
55
What is found in a pilosebacous unit?
Specialised keratins, adjacent sebaceous gland
56
What causes hair pigmentation?
Melanocytes above the dermal papilla
57
What happens in acne vulgaris?
bacteria in the hair shaft feed on the complex lipids and create small free fatty acids which can diffuse into the skin and act as a pro inflammatory signal, therefore the red boils can be treated with antibiotics to slow bacteria or by starving them by using retinoids which block the formation of sebum (mix of ceramide in sebaceous glands)
58
Describe the embryological phases of hair growth
```
Anagen= 3-7 years
Catagen = 3-4 weeks
Telogen= 50-100 per day
```
59
What influences telogen?
Changes in hormone profiles, thyroxine and androgens
| - Langulo (in utero), villus, terminal
60
Why does hair fall out in chemotherapy?
All hair goes into the telogen phase
61
What causes hair growth in PCOS?
High male sex hormones cause hair growth in areas with the receptor
62
What is alopecia areata?
Hair follicle cells are attacked by T lymphocytes
63
What are nails made of?
Specialised keratins
64
What is the nail matrix?
Zone of stem cells- exquisitely sensitive / root similar to hair bulb
65
What is the growth rate of nails?
0.1mm per day
fingers>toes
summer>winter
66
What is the dermo-epidermal junction?
interface between dermis and epidermis
67
What is the function of the dermo-epidermal junction?
>Support, anchorage, adhesion, growth and differentiation of basal cells
>Semi-permeable membrane acting as barrier and filter
>helps with diffusion of blood to the epidermis
68
What is bullous pemphigoid?
Antibody forms against the junction structures
69
What is seen in epidermolysis bullosa?
Hands are fused, knitting deformities
70
What is ground substance?
Ground Substance; proteins, hyalouronic acid, glucosaminoglycans
Found in the dermis
71
What cells are found in the dermis?
Mainly fibroblasts (make collagen and elastin), macrophages, mast cells, lymphocytes, langerhans cells
72
What other than cells and ground substance is found in the dermis?
```
Fibres- collagen and elastin
Muscles
Blood vessels
Lymphatics
nerves
```
73
What is photoaging?
Loss of collagen and lack of elastin.
| Telomere shortening.
74
What is important in elastin fibre destruction of ageing process?
UV light and smoking
75
What is an angioma?
Malformation of blood vessels, cause is unclear
76
Describe lymphatic vessels
Sub-epidermal meshed netoworks.
| Smaller non-contractile vessels-> larger contractile lymphatic trunks
77
What is the function of lymphatic vessels?
continuous draining of plasma proteins, extravasated cells and excess interstitial fluid
78
What is the immune function of lymphatic vessels?
- surveillance by circulating lymphocytes and Langerhans cells
- channelling of micro-organisms / toxins
79
What is the cause of chronic lymphoedema?
Obesity causes lack of muscle pump and accumulation of fluid
80
What are the consequences of lymphoedema?
Fragile skin can break and any time, causing ulcers
Cellulitis- bacterial infection of the lymphatics
81
What are pacinian receptors?
Pressure receptors
82
What are meissners corpuscles?
Vibration receptors
83
What do autonomic nerves supple?
Blood vessels, nerves and glands
84
What is neurofibromatosis?
Overgrowth of nerves
85
What is a blackhead?
Open comedone
86
What is a whitehead?
Closed comedone
87
What is a sebaceous gland?
Holocrine secretion opening into a pillary canal
88
Where are sebaceous glands located?
largest on face and chest
89
What are sebaceous glands sensitive to?
Hormones
90
What do sebaceous produce?
Sebum, Squalene, wax esters, TG and FFA
91
What are the functions of sebaceous glands?
Control moisture loss, protection from fungal infection
92
What do apocrine glands develop as?
Part of the pilosebaceous unit
93
Where are apocrine glands found?
Axillae and perineum
94
What are apocrine glands dependant on?
Androgens
95
What do apocrine glands produce?
Produce oily fluid odour after bacterial decomposition
96
Where are eccrine glands found?
Whole skin surface; palms, soles, and axillae in particular
97
What stimulates eccrine glands?
Sympathetic cholinergic nerve supply- mental, thermal and gustatory stimulation
98
What are the functions of eccrine glands?
Cooling by evaporation
| Moisten palms and soles to aid grip
99
How much to eccrine glands secrete per day?
can be >10L per day
100
What is acute skin failure?
Toxic epidermal necrolysis
101
What is the most common trigger for TEN?
Drugs; paracetamol, echinacea
102
What happens if the skin fails all over the body?
- Pain
- Infection
- Water balance (renal failure)
- thermoregulation
- protein loss (albumin and keratin) -> water loss into tissues and oedema everywhere
103
What is proven to extend the life of TEN patients?
Keeping them warm
104
What is erythroderma?
Red skin- covering 80-90% of the body
105
What is the most common causes of erythronderma?
T cell lymphoma
Dermatitis
Psoriasis
106
What is the epidermis a physical barrier to?
Friction, mechanical trauma
| UV radiation
107
What is the epidermis a Chemical barrier to?
Irritants, allergens, toxins
108
What is the epidermis a pathogenic barrier to?
Bacteria, viruses, fungi
109
What is steroid-sulphatase deficiency X-linked ichthyosis?
No normal lipids in the lipid layer
| Loss of barrier function
110
What can cause a syndrome like steroid-sulphatase deficiency X-linked ichthyosis?
HMG-CoA reductase inhibitors
111
What is dermatitis?
Inflammation of the skin
112
What is type 4 hypersensitivity?
Contact allergy (remember it doesn't happen on first exposure)
113
Which wavelength penetrates deepest into skin?
Longer the wavelength, deeper the penetration ; radio waves, visible light, UVA, UVB
114
The shorter the wavelength the .... the energy of the .....
higher
| photon
115
What is the ratio of melanocytes to keratinocytes in the skin?
1:10
116
Describe vitamin D metabolism in the skin?
Converted in skin at 290 to 320 nm UV in the stratum granulosum and spinous granulousm
117
Describe the thyroid metabolism in the skin
Converts T4 -> T3
| 80% conversation occurs in peripheral tissues; such as the skin
118
Describe eczema herpeticum
People with eczema are prone to infections like herpes simplex 1
119
What is scabies?
infection of the mites on the skin surface, in crusted scabies there are million son mites; this is caused by an immunosuppression
