Skin Flashcards
What is the Function of Skin
Protection
Sensation
Tehrmoregulation
Metabolic Function
What does protection involve
chemical , termal and mechical mechanisms
protection against fungal and UV
What does Sensation involve
pain - to pull away
temperature
what does thermregultion involve
insulating
give off excess heat
Metabolic Function
UV –> Vitamin D
storage of energy - fat
What is the epidermis made of
epithelial
what is the dermis made of
connective tissue
what is the hypodermis made of
loose connective tissue with adipocytes
what is the dermal paillae
projections from dermis into the epidermis
what is the epidermal ridges
projections from the epidermis to the dermis
What is the epithelium of the epidermis
simple squamous keratnised epithelium
What is the general structure of the dermis
fibrous collagenous
elastic connective tissue
can have vessels nerves receptors can include glands and ducts
what is the general structure of the hypodermis
large blood vessels
adipose tissue with septa of collagen bundles
what is the direction of the collagen to the skin surface
perpendicular
what are the 4 cell found in the epidermis
Keratinocytes
Melanocytes
Antigen presenting langerhans cells
Merkl’es cells
what is septa
anchors skin to underlying tissue
what are the different layer sof keatinocytes
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum bassale
What is the stratum basale
single layer of basophilic columnar - coboidal shape on the basal lamina
what is the function of stratum basale
intense mitotic activity
act as stem cells to constantly produce epidermal cells
how thick is the stratum spinosum / what are they
5 cells thick
polyherdal / slightly flat
what is the function of stratum spinosum
actively synthesising keratin filament
why is it spinous (spine like)
desosomes attaching each other to the cells
how many days does it take for the epidermis to renew
15 - 30 days
what do keratinocytes form
tonal fibrals
where do tonal fibrals converge and terminate
at desmosomes
what happens to stratum spinosum in high pressure areas
it is thickener
how many layers for the stratum granulosum . what is it
3 - 5 layers of flattened polygonal cells
what is their cytoplasm filled with
kertaohyaline granules
what does the keratohyaline granules have when activated
profilaggrin or filagrin
what is the function of the stratum granulosum
promotes clustering of cytokeratin tonofibrils to form keratin
what does the stratum granulosum contain
lamellar bodies
what do the lamellar bodies release
glyocholopids
what do they do
after they die they become glue and waterproofing agent
how thick is the stratum corneum / what is it
15 - 20 layers non nuclated kernatised cells
what is the cytoplasm filled with
biregringesnt filamentous keratin
these dead cells contain what
fibrillar and amorphous proteins with a thickened plasma
what is the keratin
6 different polypeptide with packed speclaised matrix
what layers if skin cancer moslty from
Basale and spinosum
what is the lucidum
layer between the granulosum and the coreum
when is this layer present
only seen in thick skin as it poorly stains
what kind of cells in the lucidrum
flattened esoinophillic cells - nulcei and organelles lost to cytoplasm
only has keratin filament
Life Cycle Keratin Basale
syntehssisng keratin filament
Spinosum Life Cycle Keratin
keratin filament –> keratohylain granules + lamellar bodies
Granulosa Life Cycle Keratin
Kertoylain left in the cytoplasm
decahrge the lamellar bodies to form a water barrier
Corenum Life Cycle Keratin
breakdown nucleus and cytoplasm
thicker plasma is formed
what is psoriasis
condition with high amount of proliferating cells in the stratum basale and spinosum
decrease in cycle time results in abnormal keratinisation
what are the two types of epidermal water barriers
Cell envelope
Lipid envelopes
What is the cell envelop made of
insoluble proteins
(loricin, keratin, filaggrin)
where are the insoluble proteins deposited
on the inner surface of the plasma membrane
what is the lipid envelope
layer of lipids
where do the lamellar bodies for a lipid envelope go
into the intracellular spaces between the stratum granulosum and stratum corneum
types of lamellar bodies for the lipid envelope
glysophoglipids , phoslipids and ceramides
what is the difference between thick and thin skin
the stratum corneum is thicker in thick skin
what are melanocytes derived from
neural crest cells
what is there appearance
pale cells with prominent dark nuclei long processes which extend to adjacent cells
what is their function
muse melanosomes to move to keratinocytes
what is a melansome
they are black and bronw pigments called melanin
what do they contain
pheomelanin (red + yellow)
eumelanin (brown + black)
Formation of mealinin - First step
Melanocytes produce lysomes related membrane bound strcutures from Golgi apparatus called premelansomes (involved in melanin syntehsis)
Formation of melanin - second step
melanin produced from tryosine by a series of reactions making ealry mealsosomes
formation of melanin third step
with maturation melasomes travel towards the end of the melaocyte process
formation of melanin fourth step
with high concentrations the melaocyte processes will invaginate into keratinocyte cell membrane
formation of melanin fifth step
Keratinocytes phagotise the tips of the melatocyte process containing melansomes
melanin formation sixth step
melanin is transfered to neighbouring kertinocytes
pigment donation
Melanin formation seventh step
once inside the keratincoytes mealsomes are released into the cytoplasm
melanin formation eighth step
melasomes are distributed within the keratincoytes with accumulations forming dark umbrellas that protect DNA from the sun UV
what are langerhans cells
resident immune cells of epidermis
what s their function
antigen presenting cells (dentires) and they replish themselves
invade the skin from bloodstream
what is their appearance
pale with irregular nuclei
where are they found
in the stratum spinosum
what do merkels cells look like
round cells with pale staining cytoplasm
what is there function
touch receptors
associated with nerve ending
where are the merkel cells found
highly tactile areas such as lips and fingertips
what are the two types of cells in the dermis
Papillary dermis
reticular dermis
what is the papillary dermis
collagen I + III
elastic fibres
extensive plexus of vessels and nerves
Reticular dermis
dense irregular connective tissue
collagen and elastic fibres
larger blood vessels
what is the hypodermis moslty made of
adipose tissue
extensive vascular supply
what else is there
septa of dense irregular connective tissue
what is its function
connect dermis to the underlying deep fascia
which one is higher the papillary dermis or retricular dermis
papillary dermis as it is closer to the epidermis to go into the epidermis