Flashcards in 9. Structure, Function and Disorder of Skin Deck (35):
How can disease affect the macroscopic variations of colour, hair and wrinkling of skin?
Colour - vitiligo (autoimmune depigmentation)
Hair - alopecia areata (autoimmune hair loss)
Wrinkling - uv-induced abnormalities (sun burn, skin ageing, skin cancers).
What is the stratum corneum made of?
Dead squamous epithelia that will flake off.
What are the five layers of skin?
Stratum corneum (horny layer), granular layer, prickle cell layer, basal layer and dermis.
What are keratins?
Heterodimeric fibrous proteins which contribute to the strength of the epidermis. They're the main constituents of hair and nail.
What cells in the skin undergo mitosis?
Keratinocytes, their daughter cells move upwards and have terminal differentiation so lose the ability to divide.
What makes up the granular layer of the epidermis?
Keratohyalin granules. Keratins, fibrous proteins and enzymes.
What is the horny layer/ stratum corneum made up of?
Layers of flattened corneocytes.
What is the transit time of keratinocytes from basal layer to stratum corneum?
What are melanocytes and langerhan cells? (Their origin, where they're found, how they're seen, what their function is).
Dendritic cells, melanocytes of neural crest origin and langerhan cells of bone marrow origin. Both cant be seen histologically without special stains. Melanocytes are in the basal layer of the epidermis and produce melanin that give the skin colour, the more melanin produced, the more tanned the skin. Langerhan cells are scattered through the prickle cell layer and present antigens to T lymphocytes so are involved in the immune response.
What stain is needed to view Langerhan cells and melanocytes histologically?
S100 monoclonal antibody staining.
What is noticeable about photomicrographs of palmar skin?
The horny layer is really thick and there are no hair follicles. The prickle cell layer is also very thick.
What is noticeable about the photomicrograph of scalp skin?
The stratum corneum flakes off as dandruff, there are lots of hair follicles and sebaceous glands.
What is psoriasis?
Abnormal epidermal growth and differentiation that affects 2% of the population.
What causes psoriasis?
Could be to do with genetics but not known yet. Extreme proliferation of epidermal basal layer and thickening of the prickle cell layer with excess stratum corneum cells (scaling). The cells have a week long cycle rather than 30-40 day cycle.
What is a possible treatment of psoriasis?
UV photo therapy.
What is allergic contact dermitis mediated by?
What is a malignant melanoma?
Malignant growth if melanocytes.
What is vitiligo?
Autoimmune destruction of melanocytes.
What causes hairs to go grey with age?
Melanocytes not functioning in hair follicles with age.
What affects the prognosis of malignant melanoma?
Whether it has gone through the epidermal basement membrane. If it hasn't, the prognosis is good, if it has, the prognosis is bad.
What makes up the extracellular matrix of the dermis?
Collagens, elastin and other extracellular matrix components.
What are the components of the dermis?
Blood vessels, lymphatic vessels, mast cell, nerves and extracellular matrix.
What are keloids caused by?
Excess scar tissue productions following wounding.
How do blood vessels in different layers of the skin differ?
In the superficial dermis, there are smaller blood vessels. In the deeper dermis there are larger blood vessels.
What causes the birth defect 'port wine stain'?
Congenital malformation of dermal blood vessels.
What causes allergic reactions?
Histamine released from cytoplasmic granules in mast cells, caused increased vascular permeability and leakage of plasma into exactravascular sites causing oedema.
What causes acne?
Sebaceous glands getting obstructed, increased serum production and infection.
What is hyperhidrosis?
Increased swearing especially on the palms and soles.
What are apocrine sweat glands?
Large sweat glands abundant in axial law, genital and submammary areas.
What are the four major function of the skin?
Barrier, sensation, thermoregulation and psychosexual communication.
How does the skin act as a barrier?
The outer epidermis prevents per cutaneous absorption of exogenous substances. It can be overcome during percutaneous absorption of drugs or in some diseases.
What does poor barrier function of the skin lead to?
Loss of fluid, protein, other nutrients and heat. Also excessive absorption of exogenous agents like drugs.
What causes loss of the sensation function of the skin?
Leprosy and diabetic sensory neuropathy.
How does the skin act as a thermoregulator?
Vascular thermoregulation (dilation of skin blood vessels leads to heat loss and constriction leads to heat gain) and thermoregulatory eccrine sweating (evaporation of eccrine sweat causes cooling).