FOUND-SKIN Flashcards
what are the functions of skin (5)?
- —>protection (from trauma/ irritants, infection , UV)
- —>temperature regulation
- —->sensory detection
- —->interpersonal detection
- —->vitamin D production
what is the role of the epidermis?
-contains cells that produce pigment and protect immune system
describe the contents of the epidermis.
- stratifies squamous epithelium
- keratinocytes derived from stem cells
- 5 LAYERS (Come Lets Get Some Bread)
how is vitamin D produced by the skin and which layer?
Vitamin D3 produced by cleavage of 7-dehydro-cholesterol by UVB
-epidermis
what does the epidermis do in response to injury or inflammation?
increased proliferation
what is the basal layer of epidermis made up of?
- single layer of cuboidal keratinocytes-produce keratin proteins
- connected to adjacent cells by desmosomes
- attached to basement membrane by hemidesmosomes
what do basal cells do?
divide to produce new keratinocytes which migrate upwards
what are desmosomes?
directly form cell to cell adhesions
what are hemidesmosomes?
hemidesmosomes form adhesions between cells and the basement membrane
how long does it take for for the basal layer to shed completely?
-4 weeks
- 2 to reach corneal layer
- further 2 until shedding
how many cells thick is the spinous layer?
5-10
describe the spinous layer
- progressive flattening of cells towards the surface
- desmosomes open to allow the passage of water and individual cell movement
describe the structure of the granular layer.
- 1 to 3 cells thick
- contains keratohyaline granules
what are the roles of the granular layer?
- prepare cells to form the corneal layer
- important layer as barrier to water loss
what does the thickness of the corneal layer depend on?
on the site of the layer
what is the structure of the corneal layer?
- semipermeable layer of the cells without nuclei
- dead keratinocytes
what is the role of the corneal layer?
- acts as a barrier
- when barrier function is disrupted function leads to disease
what are the roles of the dermis (5)?
- provide structural support
- thermoregulation
- form various elements of the immune system
- intricate network afferent and efferent nerves for sensation and control of vascular tone
- mediates itch sensation
what is the structure of the dermis?
- vascular
- comprised of connective tissue-tensile strength in multiple directions
- contains sebacous (oil) and sweat glands
what are the different cell types in the dermis?
- macrophages
- fibroblasts
- mast cells
where do melanocytes reside and what percentage of cells do they make up here?
basal layer of epidermis
10%
what do the numbers of melanocytes depend on?
racial skin type
what type of cell is a melanocyte?
form of dendritic cell
what do melanocytes do?
- produce melanosome
- melanosome synthesises melanin-absorbs UVB
what is the role of melanin?
- concentrated in basal layer
- induced by UV
- absorbs UV
what are the different types of UV and how much damage do they each cause?
- UVC-cannot penetrate skin
- UVB-penetrates skin-direct energy absorption by DNA-can cause mutations-cancer
- UVA-penetrates skin more
- visible light penetrates most
- these both cause DNA strand breaks/ oxidative damage/ base modification -can cause cancer
what is cutaneous immunosurveillance?
the immune system within skin (in healthy cells) which can repair much of the damaging effects of light
what happens when immunosurveillance fails?
greater risk of squamous cell carcinoma
where are Langerhans cells predominantly situated?
epidermis (spinosum)
where are Langerhans cells derived from?
bone marrow
what is the role of Langerhans cells?
antigen processing not antigen presenting
- important in cutaneous immunosurveillance and contact
- initiate adaptive immune response
where are merkel cells situated?
located just above basement membrane (between dermis and epidermis-basale)
what is the role of merkel cells?
rudimentary touch receptor-mechanoreceptors (pacinian and meissner’s corpuscles)
what do merkel cells contain?
neuroendocrine peptides with intracytoplasmic granules
what are 2 examples of merkel cells?
- pacininan corpuscles-deep dermis
- meissiner’s corpuscle-more superficial dermis
which cell is the primary cell of the dermis?
fibroblast
what are the roles of the fibroblasts?
- produce key components of extracellular matrix
- important in wound healing and scar formation
what type of cell is a mast cell and where does it originate from?
granulocyte
bone marrow
what is the role of a mast cell?
role in defence but also involved in allergic reactions
what are some other immune cells in the dermis?
- dermal dendritic cells
- macrophages
- lymphocytes
- neutrophils
- eosinophils
- plasma cells
- —->all play role in infection and inflammation
what are nails made of?
hard keratin
where does the nail plate grow from?
nail matrix
what are the roles of nails?
- protects the fingertip
- provides counter pressure to aid sensation
what are hairs made up of?
keratin
where is hair produced?
hair follicles
-follicular unit-also comprises of sebaceous glands and errector pili muscles
what are the 2 types of hair?
- terminal (coarse)
- vellus (fine)
how does hair grow?
in a cycle (grow/ rest/ fall out phases)
what are the functions of hair?
- protection
- sensory (eg cat whiskers)
- temperature regulation
- social
name 2 hair abnormalities?
- hirsutism-too much hair growth in antigen receptive areas-can be sign of hormone imbalance
- alopecia areata-immune system switches off hair follicles in specific area-can regrow but random
what are the 2 types of sweat glands?
- eccrine
- apocrine
what is the role of eccrine glands?
sweating allows heat loss
what is the role of apocrine glands?
sweating may be linked to pheromones-causes body odour
what does the density of glands depend on?
the site
what is a dermatome?
area of skin supplied by single nerve
what are the 3 hair generation phases?
1-TELOGEN- epidermal cells of follicle are forming
-cells of hair matrix divide and are added to the base
2-ANAGEN-hair growth phase
3-CATAGEN-hair falls off the follicle
which protein does hair generation involve?
alpha keratin
what is the role of pacinian corpuscles?
deep pressure mechanoreceptor
what is the role of meissner’s corpuscle?
mechanoreceptors, fine touch
what is the role of the end-bulbs of krause?
thermoreceptors
what is the role of ruffinis end organ?
skin stretch
what is the role of the sebaceous gland?
release sebum into skin and hair via holocrine secretion
what are the 5 layers of the epidermis?
Come Lets Get Some Bread
1-stratum CORNEUM 2-stratum LUCIDUM 3-sratum GRANULOSUM 4-stratum SPINOSUM 5-stratum BASALE
which cell types are in the epidermis?
- dead kertainocytes (s. corneum)
- lamellar granules (s. granulosum)
- keratinocyte (s. spinosum)
- langerhans (s. spinosum)
- melanocyte (s. basale)
- merkel cell (s. basale)
