SKIN Flashcards
7 functions of skin
- barrier
- immunological
- homeostatic
- sensory
- endocrine
- excretory
- drug delivery
how many layers of skin
2: epidermis and dermis
how many layers in epidermis
4 or 5
classify the epidermal epithelium
keratinized stratified squamous
where is thick skin found
palms, soles
T or F: thick skin is always hairless
T
2 layers of dermis
papillary, reticular
CT type in papillary layer
loose CT
CT type in reticular layer of dermis
dense IR CT
range of thickness of skin
< 1mm to > 5mm
T or F: skin is continuous with mucous membranes
T i.e nasal cavity
layer underneath dermis
subcutaneous layer / hypodermis (NOT SKIN)
What is the camper’s fascia
hypodermis (aka superficial fascia)
in thick skin, which layer changes width?
epidermis
if include dermis, where is the thickest skin in your body
back
which epidermis layer is in thick skin, but not thin skin
stratum lucidum
name the 5 layers of the epidermis from superficial to deep
(Stratum): corneum, lucidum, granulosum, spinosum, basale/germinativum (“Come Let’s Get Sun Burnt”)
is there a basement membrane in skin?
yes, separates epidermis from dermis
how many cells thick is the stratum basale
1
what layer of skin has the dead cells
corneum
predominant cell type in epidermis
keratinocyte
function of keratinocyte
produce keratin (waterproof barrier)
merkel cells: what layer and what type of skin
germinativum/basale ; hairless skin
what kind of protein is keratin
intermediate filament
inside vesicles of merkel cells
neuroactive chemicals
what causes merkel cells to release their vesicles
touch
what is the result of merkel cells vesicle release
stimulation of afferent nerve endings
merkel cells = _____ receptor
touch
what epidermal layer has langerhans cells
spinosum
what body locations have langerhans cells in their epidermis
keratinized skin, mucous membranes, superficial lymph nodes
what epidermis layers contain melanocytes
basale, but some melanocytes and their cell processes extend into spinosum
ratio of melanocyte: keratinocyte in s. basale
1:4 -1:10
function of melanocytes
produce melanin, package into melanosomes
what is pigment donation
melanocytes give melanosomes to keratinocytes
where do keratinocytes store melanosomes? why?
“supranuclear”; above their nucleus; shield from UV radiation
fate of melanosomes in keratinocytes
degradation by lysosomes
T or F: some body parts have more melanocytes
true; adaptation
what does tanning do to melanocytes
more active; NOT MORE IN NUMBER
sunburn = _____
inflammation
keratin produced on ____ _________
free ribosomes (protein stays in cell)
keratin intermediate filaments (cytoskeleton) are called
tonofilaments
what types of cell junctions connect keratin
desmosomes (connect adjacent cells), hemidesmosomes (connect cell to BM)
T or F: melanocytes have pale cytoplasm
T; surprisingly
T or F: epidermis has no blood supply
T
why does s. spinosum look “spiky”
tissue processing; cells shrink when dehydrated , but desmosomes stay in tact
what is produced in s. spinosum on free ribosomes
keratinohyalin ; have IF-associated proteins
what forms on RER in s. spinosum
lamellar granules (pro-barrier lipids)
what 2 types of granules made in s. spinosum
keratinohyalin, lamellar
in what layer are lamellar granules released
granulosum
what happens at junction of s. granulosum and s. corneum
granulocytes (keratinocytes in s. granulosum) converted to cornfield cells
cell shape in basal layer of epidermis
cuboidal
how long does it take for cells to become cornfield in s granulosum
2-6 hours
T or F: cells in s. granulosum have nuclei, organelles
T, until cornified
keratinization in s. granulosum produces ____ ______
soft keratin
what do the keratinohyalin granules do in granulosum
IF-associated proteins promote keratin filaments -> tonofibrils & desmosomes (maintain adhesion)
3 cellular changes in s. granulosum
breakdown of nucleus & other organelles,
cell membrane thickens
acidification of cytoplasm
what holds cells together after s. granulosum
desmosomes
some people consider s. lucidum component of s ____
corneum
s. corneum consists of ____keratin
soft
pH in s. corneum
low
how does pH contribute to shed
pH dependent enzymes break down desmosomes, keratinocytes shed
how long do cells stay in s. corneum
2 weeks
where is hard keratin
nails, hair
T or F: keratin prevents 100% of water loss
F; some evaporation; insensible perspiration (loss of fluid, not through glands)
in thick skin, how long does it take from basal to shed keratinocyte?
4-6 weeks
how does blood affect skin colour
BV density, colour of blood
carotene is precursor for _____ _
vitamin A
where does carotene accumulate
keratinocytes, adipocytes
what happens if you eat too many carrots or squash
carotene => orange-is tinge to skin
T or F: darker-skinned humans have more melanocytes
F; dark skin = more active melanocytes -> more melanin (like tanning)
eumelanin ->
dark
pheomelanin
yellow/red
what 2 features of skin increase epidermal-dermal surface area
epidermal ridges, dermal papillae
what does thick skin have to increase SA between dermis and epidermis
dermal ridges (fingerprints)
term for contact between epidermal ridges and dermal papillae
interdigitation
purpose of increasing SA between dermis and epidermis
epidermis = avascular; depends on diffusion to and from dermis (nutrients, gases, waste removal)
function of dermal ridges
palms and soles endure greatest friction; want to bind epidermis and dermis tightly
CT of papillary dermis
loose CT
CT of reticular dermis
dense irregular CT
what layer of skin made into leather
reticular dermis
what 2 layers is cutaneous plexus between
dermis and hypodermis (like barrier between cutaneous (skin) and subcutaneous)
where is sub papillary plexus
under papillary of dermis
what BV control superficial blood supply
AV anastomoses from cutaneous -> subpapillary
2 types of BV plexus in dermis
cutaneous and subpapillary
what BV in dermal papillae
capillary loops
what type of innervation in dermis
sympathetic ONLY (think: scared cat -> arrector pili -> hair up)
3 things innervated in skin
arrector pili
vascular smooth muscle
glands
CT of hypodermis/ superficial fascia
loose CT with adipose tissue
from centre, state 7 layers of hair
medulla (soft keratin), cortex (hard keratin), cuticle, internal root sheath, external root sheath (e=epidermis, continuous with), glassy membrane (thick BM), dermis-derived CT
What determines length of uncut hair
Anagen (growth phase)
Why does hair in axillae not grow as long as hair on head
Shorter growth phase (4 months vs 3-6 years)
T or F: melanin production decreases with age
T
hair follicle is invagination of _____
epithelium
what provides attachment for arrector pili muscle
dense CT sheath
name for terminal dilation of hair follicle
hair bulb
function of dermal papillae (under hair bulb)
provide BVs, nerves for hair
what kind of cells in hair matrix
epithelial cells (basal cells, melanocytes)
other than soles and palms, what other hairless places in body
glands penis, labia minora, clitoris
what epidermal layers involved in hair follicle
basale and spinosum
what layer produces the sheath around the hair follicle
CT dermis
