Structure and Function Flashcards
What is the order of skin layers and where is the stratum lucidum present vs not present?
Stratum basale -> spinosum -> granulosum -> lucidum -> corneum
Stratum lucidum only present in palmar / plantar skin (acral regions)
How quickly does skin turn over?
14/14 rule
14 days from basal layer to granulosum layer
14 days as corneum -> exfolitation
What is keratin made of? What amino acid are they high in?
It is an intermediate filament composed of acid and basic cytokeratins
-> one of each type which associate together to form heterodimers of keratin filaments
High in cysteine -> form many disulfide bonds
Where in the body are the highest concentrations of melanocytes? Are there melanocytes outside of skin?
Face / forearms (sunexposed areas), also genitals (protect basal epithelium of genitals)
Yes there is melanin outside of the skin (i.e. brain / GI tract) and probably have an immunologic function.
Does darker skin have more melanocytes? How does this work?
Same number of melanocytes, they are just dispersed differently
What enzymes are important for the beginning of melanin synthesis?
- Tyrosinase -> converts tyrosine to DOPA
2. DOPA oxidase -> converts DOPA to DOPA quinone
Where are melanocytes situated and what is their morphology?
Sit along basal cell layer of epidermis, morphology is dendritic
Have melanosomes which are eaten by keratinocytes
What is a Merkel cell and what does it look like by EM?
It is a dispersed cell type which functions as a touch receptor.
Has dark granules by EM
What is the purpose of the dermal papillae forming ridges?
Gives the epidermis structural rigidity so it doesn’t just slide off to friction
What is the predominant collagen present in the basement membrane and dermis?
Basement membrane - Type IV collagen
Dermis - Type I collagen. Dermis also contains T3 collagen and elastic fibers
What is the basic microscopic structure of collagen?
Basic structure is Gly-X-Y, where X/Y are USUALLY proline are lysine, which get hydroxylated in a vitamin C dependent process
Where are apocrine glands located typically? When do they become active and what do they release? Are they smelly?
Located in axilla, areola, and nippile of mammary gland, also anus / external genitalia
They become active around puberty, under hormonal and adrenergic control
They are not smelly unless bacteria degrade the products they release (by merocrine secretion) for odor
What is one treatment for excessive sweating and why does this work?
Brides often have botox injections in sweaty areas.
Eccrine sweat glands are under control of SANS post-synaptic ACETYLCHOLINE release which can be blocked by botox, preventing sweating
What is the order of UVA / UVB / UVC by wavelength? Where is UVC found?
UVA longer than UVB longer than UVC
UVC is the shortest wavelength and is used in germicidal lamps
It does not reach the surface of the earth typically
What is UVB / UVA and which is in highest proportion? Is it blocked by glass? How far in the skin does it penetrate?
UVB = UV burn -> 5%, causes sunburn, penetrates epidermis, predisposes most to skin cancer, only this one is blocked by glass
UVA -> 95%, found in tanning beds, mostly causes photoaging by penetrating deep to dermis. Skin cancer less likely but still possible
