specialised tissues Flashcards
skin: explain the structure and function of the skin, explain the mechanisms by which integrity is maintained, and recall the development, function and control of melanocytes
what other organ systems does skin have complex interrelationships with
endocrine, immune, vascular, neural
layers of skin
epidermis (basement membrane), dermis, subcutis
structures within the skin
pilo-sebaceous unit, sweat glands, melanocytes, Langerhans cells, desmosomes, keratinocytes, lymphatics, nerves
structure of pilo-sebaceous unit
follicle, hair shaft, sebaceous gland and pilo erecti muscle
types of sweat glands
apocrine: watery; eccrine: viscous, breaks down bacteria, contains pheromones
skin functions
protection against injury; protection against pathogenic organisms; waterproofing and fluid conservation; thermoregulation achieved by regulation of blood flow (under sympathetic control), sweating, shivering and behaviour; protection against radiation, absorption of UV radiation and vitamin D production (deficiency causes rickets); surface for grip; sensory organ; cosmetic
where is the epidermis derived from
ectoderm
where is the epidermis
on skin surface
what 4 layers are keratinocytes in within the epidermis (from deep to superficial)
stratum basale, spinosum, granulosum, corneum
keratin proliferation within the epidermis
move up epidermis to corneum and differentiate: basal cell → prickle cell → granular cell → keratin
cells and their location within the epidermis
dendritic cells: melanocytes (melanin; stratum basale); Langerhans cells (APC; spinosum); Merkel cell (sensation; stratum basale)
what is in beyween keratinocytes
“glue” of lipids and proteins (incl. filaggrin)
what is the function of the “glue”
barrier function to prevent infection, allergies and conditions such as eczema (caused by filaggrin gene mutation which causes palmar hyperlinearity)
what is the basement membrane zone also known as
dermo-epidermal junction
where is the basement membrane zone
where epidermis attaches to dermis
what attaches the epidermis to the dermis and how is this achieved
hemi-desmosomes; anchor plaques and many proteins incl. tonofilaments and anchoring fibrils
what happens if a protein is defective withing the basement membrane zone
genetic conditions which is repaired with scar tissue
what causes premature death from skin cancer
constant inflammation
where is the dermis derived from
mesoderm
what does the dermis contain
supportive connective tissue: collagen, elastin and glycosaminoglycans synthesised from fibroblasts
structure of dermis from superficial to deep
papillary → reticular → hypo fat layer
what immunocompetent cells are present in the dermis
dermal dendritic cells
what is the subcutaneous layer
connective tissue and fat
what are melanocytes and where are they
dendritic cells within epidermal basal layer
where are melanocytes derived from
neural crest
where is melanin produced within melanocytes
melanosomes
pathway of melanin to adjacent keratinocytes
melanin packaged into granules → move down dendritic processes → transferred by phagocytosis to adjacent keratinocytes
what do melanin granules do
form protective cap around keratinocyte nuclei to protect DNA from UV
what does this protective cap lead to
skin pigmentation
what influences variation in racial pigmentation
number and size of melanosomes
