Intro to Derm- Development and structure of skin Flashcards
From which embryological elements does the skin arise? (Epidermis and dermis)
Epidermis from ectoderm and dermis from mesoderm (which comes in contact with inner surface of epidermis).
What is the essential role of the mesoderm in the development of the skin?
Induces differentiation of epidermal structures, like the hair follicle.
By which week is the epidermis formed?
week 4 (single layer of cuboidal cells)
What is the periderm, what is its function and when does it develop
A secondary layer of squamous, non-keratinising cuboidal cells. It develops in week 5. It’s function is to produce a waxy white protective substance, vernix caseosa
What is the stratum germintivum, when does it form and what does it do
It forms from week 11, it is the basal layer of cuboidal cells and proliferates to make 4 more layers of strata.
What are the 5 stratum layers called.
corneum, lucidum, granulosum, spinousm and germinativum (come lets get some beers)
Where is the stratum lucidum found
only on hands and feet
What are melanocytes and where are they derived from?
melanin producing cells, derived from melanoblasts from the neural crest
When do melanoblasts migrate and to where and to form what?
migrate dorsally to form dermis and epidermis
What is the use of melanocyte stem cells and where are these found?
to replenish differentiated melanocytes, these are found in the hair follicle bulge.
How is the synthesis of eumelanin regulated?
alphaMSH and ACTH activate MCR1 by antagonist, which induces the melanogenic cascada. This stimulates the synthesis of eumelanin.
How does melanocortin 1 receptor (MC1R) work and how does it regulate melanins?
It is a G-coupled receptor, regulated by alphaMSH and ACTH. Its activation results in the melaogenic cascade which ending the production of melanins.
How does POMC regulate melanin production?
POMC is the hormone which regulate the repase of alphaMSH and ACTH
What does agouti signaling protein (ASP) do?
reserves the effects of ACTHand alphaMSH, to cause the production go pheomelanin.
How does UV exposure regulate melanocyte/melanin content?
Increases melanin production by increasing the expression of transcription factor MITF (and downstrain melanogenic products like TYR and TRP1)
What layers is the dermis divided into?
papillary and reticular
Which cells make up the epidermis?
keratinocytes, in different stages of differentiation
What differentiates the different layers of the basal layer?
Only place where cell division takes place
What is special about the stratum corneum?
It’s cells have no nuclei or organelles
How long does it take cells to go from the basal layer to the surface more or less? When does this accelerate?
30 days, accelerates with skin disease (eg psoriasis)
What forms the cytoskeleton of keratinocytes?
actin and tubular microtubules and intermediate filaments made of keratins
What are desmosomes? What is their function?
adhesion complex in epidermis, which allows cells to withstand damage and anchor keratin intermediate filaments to cell membrane and bridge adjacent keratinocytes
What are adherences junctions?
transmembrane structures and actin skeleton
What are gap junctions?
intercellular channels which form direct connections between the cytoplasms of adjacent keratinocytes
What is the function of melanocytes?
to distribute melanin pigment to keratinocytes
What is the function of langerhans cells?
immune response-APCs
What is the function of Merkel cells?
mechanosensory receptors
What proteins and glycoproteins make up the basement membrane of the skin?
collagens, laminin and integrins
What is the role of the basement membrane?
cell adhesion and cell migration
What two layers can the dermis be divided into? Which layer has less vascular supply? Which one is most superficial? Which one has the most connective tissue? Which one is bigger?
papillary and reticular. the papillary dermis is most superficial has less connective tissue and more vascular supply. The largest layer is the reticular dermis.
Which proteins are present in the dermis? Which one is predominant?
collagen and elastic fibres 8elastin, fibrillin)
What are the functions of the glycoproteins in the dermis?
to facilitate cell adhesion and motility (eg fibulin)
What makes up the ground substance?
glycosaminoglycan and proteoglycan
What is the function of fibroblasts?
to generate connective tissue and repair tissue from injury.
