Skin (RA) Flashcards
What are the 4 classes of tissues in the body?
1 - Epithelia.
2 - Connective tissue.
3 - Muscles.
4 - Nervous system.
List 8 functions of skin.
1 - Protection against infections.
2 - Protection against abrasions.
3 - Protection against radiation.
4 - Preventing dehydration.
5 - Synthesis of nutrients e.g. vitamin D.
6 - Insulation / thermoregulation.
7 - Sensation.
8 - Psychosexual communication.
List 4 factors that affect skin colour.
1 - Ethnicity.
2 - Site of the body.
3 - Exposure to radiation.
4 - Drugs.
List 4 factors that affect hairiness.
1 - Site of the body.
2 - Gender.
3 - Age.
4 - Medical conditions, e.g. alopecia areata.
What are the types of skin?
1 - Hairy skin (most of the body).
2 - Glaborous skin (e.g. palms and soles of feet).
Define dermatome.
An area of skin supplied by sensory nerve fibres from a single spinal nerve (neural level).
Which spinal nerve root supplies the diaphragm?
C3-C5.
Which spinal nerve root supplies the shoulders?
C5-C6.
Which spinal nerve root supplies the wrists?
C8-T1.
Which spinal nerve root supplies the nipples?
T4.
Which spinal nerve root supplies the umbilicus?
T10.
Which spinal nerve root supplies the knees?
L3-L4.
Which spinal nerve root supplies the muscles necessary for knee flexion?
S1.
Which spinal nerve root supplies the great toes?
L5.
Which spinal nerve root supplies the feet?
S1-S2.
What is the difference between alopecia areata and alopecia universalis?
Universalis causes complete loss of hair on the scalp or body, whereas areata only affects small areas.
What are the 3 gross layers of skin?
1 - Epidermis.
2 - Dermis.
3 - Hypodermis.
Which type of epithelium is skin made of?
Keratinised stratified squamous epithelium.
What are the four layers of the epidermis?
1 - Stratum corneum (horny layer).
2 - Stratum granulosum (granular layer).
3 - Stratum spinosum (prickle cell layer).
4 - Stratum basale (basal layer).
In which layer of skin does most keratinocyte mitosis occur?
The stratum basale.
What happens to newly formed daughter keratinocytes shortly after they are formed?
They move upwards to (partially) form the stratum spinosum, where terminal differentiation begins.
What do keratinocytes synthesise and what is the function of their secretion(s)?
Keratin, which contributes to the strength of the epidermis.
How are blisters formed?
The epidermis separates from the dermis as a result of friction, allowing accumulation of fluid.
What is the stratum spinosum formed of?
- Terminally differentiating keratinocytes (at this stage are known as prickle cells).
- Prickle-like desmosomes (intercellular junctions).
What happens to keratinocytes in the granular layer?
- Keratinocytes lose their phospholipid bilayer.
- Keratinocytes differentiate into corneocytes, the main cells of the stratum corneum.
What does the granular layer contain?
- Keratohyalin granules.
- Corneocytes.
What are keratohyalin granules?
Aggregations of:
1 - Keratin.
2 - Other fibrous proteins, such as filaggrin and involucrin.
3 - Enzymes, which degrade the phospholipid bilayer (phospholipase) and cross link proteins.
What does the stratum corneum contain?
Flattened corneocytes.
What is the transit time of a keratinocyte from the basal layer to the stratum corneum?
30-40 days.
What are melanocytes, what is their function and where are they found?
- Dendritic cells of neural crest origin.
- Found in intervals in the basal layer.
- Produce melanin to give the skin its colour and protect against radiation.
How do melanocytes differ in people with different skin colours?
In people with darker skin, there are roughly the same number of melanocytes but the melanocytes produce more melanin.
What are Langerhans cells, what is their function and where are they found?
- Antigen presenting dendritic cells of bone marrow origin.
- Found scattered throughout the prickle cell layer.
- Present antigens to T lymphocytes.
- Mediate immune reactions, e.g. allergic contact dermatitis.
What is psoriasis?
- A genetic condition causing abnormal epidermal growth and differentiation.
- Characterised by extreme proliferation of the basal layer, causing gross thickening of the prickle layer and subsequent production of corneocytes.
- Manifests clinically as excessive scaling.
What is vitiligo?
- An autoimmune destruction of melanocytes.
- Often shows a symmetrical pattern.
Why does hair become grey with age?
Melanocytes stop functioning in hair follicles with age.
With a malignant melanoma?
What is associated with a good prognosis?
- Cancer of melanocytes.
- A good prognosis is associated with retention of malignant melanocytes above the epidermal basement membrane.
What is the dermis composed of?
- Fibroblasts secreting an extracellular matrix.
- The extracellular matrix is mostly type 1 collagen and elastin.
- Blood vessels.
- Lymph vessels.
- Mast cells.
- Nerves.
What is solar elastosis?
Damage to collagen and elastin due to excessive ultraviolet exposure.
What are keloids?
Grossly excessive scar tissue production following wounding.
What are scars composed of?
Mainly collagen.
Which layers of the skin are vascularised?
The dermis downwards.
What are birthmarks caused by?
Congenital malformations of dermal blood vessels.
Where in the skin are mast cells found?
In the dermal blood vessels.
What happens when mast cells are activated?
- They release histamine.
- This causes increased vascular permeability.
- This causes leakage of plasma into extravascular sites.
- This may cause angio-oedema and urticaria.
What is an angio-oedema?
Oedema of the deep dermis.
What is urticaria?
A skin rash, AKA hives.
What is the pilosebaceous unit composed of?
A hair follicle and a sebaceous gland.
What are the two types of sweat gland?
Eccrine and apocrine.
What is the cause of alopecia?
An autoimmune attack against fair follicles.
What happens to hair follicles in acne?
They become obstructed.
What are holocrine secretions?
Holocrine secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen.
What causes acne?
- Abnormal differentiation of sebaceous gland ducts, which become obstructed,
- Increased sebum production.
- Infection with normally harmless skin bacteria.
List 4 differences between apocrine and eccrine sweat glands.
1 - Apocrine glands secrete fluid onto hair follicles whereas eccrine glands secrete fluid onto the skin surface.
2 - Apocrine glands only occur in the axillary, genital and submammary areas whereas eccrine glands occur all over the skin.
3 - Apocrine glands are bigger. than eccrine glands.
4 - Apocrine secretions are more viscous (proteins and fatty acids) and eccrine glands are more watery (NaCl and water).
What is hyperhidrosis?
Increased sweating.
What is the final state of differentiation of keratinocytes?
Corneocytes.
What is the function of merkel cells?
To sense light touch.
What are cornified envelope proteins?
- Surround the corneocyte and are filled with water-retaining keratin proteins.
- Attached together through corneodesmosomes.
- Surrounded in the extracellular space by stacked layers of lipids.
What is the function of prickle cells?
How is this function achieved?
- Serve a physical and biological barrier by preventing penetration of irritants and allergens and by preventing water loss.
- Achieved via keratin production and via the binding of cells via desmosomes.
What are glands of Moll?
- AKA ciliary glands.
- At the margin of the eyelid, they secrete lipid that adds to the superficial layer of the tear film, preventing evaporation.
- Also keep the eyelashes supple.
What is a stye?
Swelling of the glands of Moll caused by a blockage.
