ToB - Skin Flashcards
What epithelia are on the epidermis of he skin and what are they made of?
Stratified squamous keratinised epithelia made from keratinocytes and their products.
What are the 4 layers of the epidermis?
1) . Stratum corneum
2) . Granular layer
3) . Prickle cell layer
4) . Basal layer
What cells are present in the epidermis and where?
1) . Melanocytes
- produce melanin from melanosomes
- dendritic cells of neural crest origin
- occur at intervals through basal layer
2) . Langerhan cells
- present antigens to T lymphocytes in allergic reactions
- are dendritic cells of bone marrow origin
- scattered through the prickle cell layer
BOTH ARE HARD TO SEE
How are the skins layers formed?
1) . Mitosis of keratinocytes in basal layer pushes new keratinocytes into prickle cell layer.
2) . These prickle cells are now joined via desmosomes = connects cells keratin to form intercellular junctions.
3) . Keratinocytes differentiate
- -> can no longer divide
- -> produce keratin
4) . In granular layer, phospholipase breaks down cell membrane of keratinocytes = differentiate to form corneocytes.
5) . Stratum corneum is formed from flattened corneocytes.
What are the features of corneocytes in stratum corneum?
Flattened
No nuclei
Mostly keratin
How long does it take for a cell in the basal layer to be sloughed off from skin?
30-40 days
What are the disorders of the epidermis?
1) . Psoriasis - extreme proliferation of basal layer and therefore all layers thicken.
2) . Vitiligo - autoimmune attack on melanocytes = depigmentation
3) . Malignant melanoma - malignant growth of the melanocytes (poor prognosis if it penetrates the basal layer) which is more common in whites than blacks as melanosomes break down easier.
4) . Allergic contact dermatitis - mediated by Langerhan cells, often in response to nickel.
How is the dermoepidermal junction best seen?
Using PAS stain
What is the dermoepidermal junction?
The epidermal basement membrane which joins the dermis and epidermis.
What are the skins functions?
1) . Barrier
- water and microbe proof
- needs overcoming for pharmaceutical cream
- disrupted by disease
2) . Psychosexual communication
3) . Sensation
- affected by leprosy and diabetic neuropathy
4) . Thermoregulation
- vascular thermoregulation
- eccrine sweating
- psoriasis can cause permanent dilation
What is the dermis made mostly of?
Extracellular matrix
What does the extracellular matrix of the dermis contain?
1) . Nerves
2) . Collagen
3) . Elastin
4) . Blood and lymphatic vessels
5) . Mast cells
What gives straie and solar elastosis in the skin?
Damage to the collagen or elastin in the dermis of the skin by UV light.
What is a port wine stain?
Where blood vessels are permanently dilated
Where are mast cells found and what do they contain?
Found surrounding blood vessels and contain granules of histamine, which are activated by allergic reactions
= local oedema due to increased vascular permeability
= urticaria
= angio-oedema
What is the extracellular matrix of the dermis formed by?
Synthesised by fibroblasts
What sizes are the blood vessels found in the dermis?
Smaller in the superficial dermis, larger as you go deeper
How are scars formed?
By the synthesis of collagen from fibroblasts. If excess is produced, keloids form.
What are the appendages of the skin?
1) . Nails
- mostly keratin
2) . Apocrine sweat glands
- wider lumen than eccrine sweat glands
- no specific function
- secrete odourless liquid from armpits, genitalia, sub mammary glands
3) . Eccrine sweat glands
- secrete water onto skins surface for latent heat evaporation = cooling.
4) . Pilosebaceous unit
- sebaceous gland feeds sebum onto hair shaft via holocrine secretion
What are disorders of the skins appendages?
1) . Acne
- abnormal differentiation of the sebaceous gland ducts
- increased sebum production can get infected.
2) . Hyperhydrosis
- excessive sweating, often from palms
What adaptation do epithelial cells have that aid sweat glands?
Myoepithelial cells = have actin filaments so can contract to push sweat out.
What is alopecia areata?
An autoimmune attack on the hair follicles
What are the macroscopic differences in people’s skin and how does it vary?
Colour - site, ethnicity, exposure to UV light
Hair colour - site, age, ethnicity
Wrinkling/laxity - site, age, exposure to UV light
THESE CAN INFLUENCE SUSCEPTIBILITY TO DISEASE
