Skin Flashcards
Functions of the skin (6)
- protection for underlying tissues against abrasions, impact, fluid loss and chemicals; keratin - abrasion, water repellant, Melanin - UV rays
- Vitamin D synthesis
- Excretion of salts, sebum, water
- Thermoregulation
- Sensation
- Storage of fats
What kind of cells is the epidermis made up of
Stratified squamous epithelium of keratinocytes (cells that contain keratin)
Does the epidermis have a blood supply
No
where does the epidermis get its nutrients from
the vasculature of the dermis
What are the 5 layers of the epidermis
Corneum, leusedum, granulosum, spinosum, basale
What does the stratum basale do
it is columnar cells which divide and daughter cells migrate up to replenish the layer above. Where the Melanocytes are found
what does the Stratum spinosum do
Linked together by desmosomes, the cells become increasingly spiky/flattened as they move upwards
What does the stratum granulosome do
dehydrates cells further, keratin fibres cross link, waxy material is secreted into the ECM
What does the stratum lucidum do
Is in thick skin which is palms of feet and hands, Is an extra leyer
What does the stratum corneum do
it is dead cells with no nuclei. layer can be easily removed with tape
why is the epidermis wavy
to increase surface area so it can get resources from dermis blood supply
What do desmosomes do?
Anchor neighbouring cells in the epidermis
what do hemidesmosomes do
anchors the stratum basale to the dermis
what are the two layers of the dermis
Papillary layer - consists of highly vascularised tissues (for nourishment)
Reticular layer - mesh like structure os collagen and elastin fibres
Both layers contain blood vessels, lymphatics, sensory nerve fibres and accessory structures.
What are the two plexus of the skin
The cutaneous plexus which is between the hypodermis and the dermis and supplies the lower dermis and hypodermis with blood
The sub papillary plexus which branches off the cutaneous plexus located deep to the papillary layer supplying blood to the upper dermis and epidermis
Hypodermis purpose
The main function is thermoregulation as it contains fat to act as insulation
Also where injections go to.
Mainly consists of adipocytes
First degree burn
Superficial - only involve the epidermis
Red, pink, dry, painful
skin remains intact
heals 3-10 days
Second degree burn
Normal: Epidermis and some dermis
Painful, moist, red, blistered
usually 1-2 weeks to heal; needs good dressing to avoid infection
Deeper: Epidermis and entire dermis
whiteish waxy looking areas
may lose sensation and get scarring
1 month to heal
Third degree burn
Full thickness burn ie. all layers of skina dn may involve some muscle and bone
waxy white to deep red or black
Hard, dry and leathery
no pain due to sensory nerve endings being destroyed
may require skin grafting and weeks to regenerate + scarring
Accessory structures of the skin
Hair, sweat glands, receptors, nails
What is Hair made of
dead, keratinised cells
Anatomy of hair follicle
hair shaft projects from follicle
Also has arector pilli muscles which when contract cause hair follicle to stand up and goose bumbs
And root hair plexus - a collection of nerves at the base for sensation
Sebaceous glands - produce sebum
Sebum
Oily secretion from sebaceous glands
Nourishes hair shaft and naturally moisturises skin
water repellant
Sweat glands
Eccrine - found in most areas of the skin
Apocrine - founs in armpit, nipples and groin
Apocrine sweat glands
Found in armpit, groin and around nipples
Secrete sticky, oily and sometimes odourus secretions into base of hair follcle
more deep one
secreted by hormones
Eccrine sweat glands
Found all over the skin
pour water secretions directly on skin surface
Located more superficially
imporatnt for thermoregulation
Has antibacterial action
Nails
Protect fingertips and toes
Enhance sensation by creating backboard
Skin aging
Thinning epidermis
Thin dermis (sagging and wrinkling) - reduced collagen; so not holding it as tight anymore
Slower skin repair
Drier epidermis
impaired cooling; less sweat
Less pigmentation (due to low melanin production); pale skin, grey hair
What does melanin do
absorbs UV light; protecting cells from UV damage
Where is melanin produced
Melanocytes in the stratum basale
How is melanin transported to epidermal cells
Melanosomes - vesicles containing melanin
Do melanocytes or melanosomes get shed
mELANOSOMES AS FOUND THROUGH THE EPIDERMIS
What is a mole
cLUSTER of melanocytes
Over poliferation can be caused by sun exposure
What is a freckle
Melanocytes over producing melanosomes
over production caused by sun exposure
Vitamin D purpose
essential for normal calcium metabolism and strong bones
What does Vit D deficiency cause
causes rickets - due to calcium deficiency and affects mood
What is required for Vit D synthesis
UV exposure
2 types of skin cancer
Basal cell carcinoma and malignant melanoma
Basal cell carcinoma
Quite common but metasis (spread) is rare (benign)
Originates in the stratum basale
Malignant melanoma
Rare but deadly of not treated
Orginates in melanocytes
Highly metastatic
mortality rate dependent on tumour
Tattoo
has to go into dermis so that it doesn’t get shed off
What are the prmiary mechanisms for heat transfer
Radiation, evaporation, convection and conduction
Radiation
increased vasodilation for heat transfer
Evaporation
of sweat
Convection
aIRFLOW takes heat away - reduced by goosebumps
Conduction
Touching something cold
to keep warm blood flow to skin is:
and how:
Reduced - by constriction of smooth muscle bands around arterioles and pre capillary sphincters in the dermis
relaxation does the opposite for heat loss
What system controls skin blood flow
Sympathetic nervous system
Which hormone control skin blood flow
noradrenaline - which acts on a1 adrenergic receptors on the vascular smooth muscle of the skin
Vasoconstriction
the blood vessels reduce blood flow which controlled by increased sympathetic nervous system activity
Vasodilation
tHE BLOOD vessels incease blood flow in response to increased temp and controlled by a decrease in SNS activity
