what are the 2 types of skin?
Glaborous skin
hair bearing skin
what are glamorous skin?
palm and soles
thick epidermis
hear bearing skin _____ depending on site
differs
Stratified squamous epithelium is constantly _____
growing
Stratified squamous epithelium contains ___…
no blood vessels , fed by vessels in the dermis
Stratified squamous epithelium skin turnover is …
52-75 days
what cells are in the epidermis ?
keratinocytes
Melanocytes
Langerhans Cells
epidermis is a barrier for?
water loss and infection
epidermis is colonised by?
microorganisms,
e.g. Staphylococcus epidermidis
what does a structure of a dermis contain?
blood vessels Nerves hair follicles smooth muscle Glands lymphatic tissue
what loose connective tissue is in the dermis?
collagen
elastin
reticular fibers
what do Arrector pili muscles
do in the dermis?
attached between hair papilla and epidermis
contract, hair pulled upright – goose bumps
what do sebaceous glands
do in the dermis?
sebum (lipids and waxy substances)
lubrication, water-proofing, softening, bactericidal
what glands does the dermis have?
sebaceous glands
sweat glands
what is the outermost layer of the dermis?
papillary layer
papillary layer ….
extends into the epidermis supply epidermis with nutrients papillary ridges ( finger and foot prints)
what’s a dense layer the dermis has?
reticular layer
reticular layer facts…
continuous with the hypodermis contains the bulk of the structures e.g. sweat glands irregularly arranged fibres resists stretching
where is the hypodermis located?
below dermis
where is the hypodermis made from?
Loose connective tissue and elastin
what does the hypodermis do?
Attaches skin to bone and muscle
Supplies skin with blood vessels and sympathetic nerves
what are three cells found in the hypodermis?
Fibroblasts, macrophages and adipocyte
How do we get pigment?
melanin form melanocytes
melanosomes transfer to keratinocytes
what does melanin protect us from?
UV light
what can the skin absorb ?
Oxygen, nitrogen and carbon dioxide
Drugs can be administered through the skin
important site of transport in many other organisms
what can the skin store and synthesise?
storage centre for lipids and water
synthesis of vitamin D by action of UV
what can the skin excrete?
urea in sweat
Sodium chloride in sweat
Lactic acid in sweat
what’s the average body temperature supposed to be ?
36.5 C to 37.5 C
what does body temp have to be maintained between ?
+- 0.6 c
what is skin temperature dependent on ?
dependent on outside temp
what is body temperature controlled by?
regulating the balance between heat production and heat loss
what’s Basal Metabolic Rate
?
Rate of metabolism of all cells
what extra metabolic rate?
Muscle contractions Activity in deep organs Hormone Adrenaline, noradrenaline and sympathetic stimulation of cells Digesion, absorption and storage of food
How does heat loss happen?
Transfer of heat from core to skin
via blood flow
order of skin formation
epidermis
papillary loops
dermis
papillary plexus
How does heat from skin go to surroundings?
radiation
conduction
convection
evaporation
what percent of heat is lost through radiation and how?
60% (nude)
lost as infrared heat rays
where is heat from conduction lost too and what percent?
3% to solids
15% to air
How Is heat lost through convection?
hot air to rises
increases with wind velocity
In what ways does our body evaporate heat and how much?
sweating
600-700ml skin and lungs a day
what’s lost in sweat ?
sodium chloride 15-30g
sweating involved stimulation of the _____
hypothalamus
what does the hypothalamus contain?
heat sensitive neurons - anterior
1/3 cold sensitive
when temp increases how does the firing rate of the hypothalamus increase?
2-10 folds
where are thermoreceptors found?
skin and deep tissue
what thermoreceptors signal to the posterior hypothalamus?
peripheral tissues
if its too hot the hypothalamus will start…
Vasodilation
Sweating
Pilorelaxation
Inhibition of shivering
Inhibition of chemical
thermogenesis
if its too cold the hypothalamus will start…
Vasoconstriction Piloerection Shivering chemical thermogenesis Increased thyroxine
what happens when you have a epidermal wound?
Basal epidermal cells leave basal membrane
Enlarge and migrate
Contact inhibition
Other cells divide to replace those moving
Continues until wound is resurfaced
Occurs within 24-48 hours of injury
what are the four phases of wound healing?
inflammation
migration
poliferation
maturation
How does a wound heal ?
- bv dilate, phagocytes invade
- scab, epithelial cells and fibroblasts migrate, fb synthesis collagen and glycoproteins
- growth of epithelial cells an bv, deposition of collagen fibres
- scab gone, cf organised, bv normal
what are some problems that can happen when a wound is healing?
Ischaemia
Dry wound environment
Infection/foreign body
poor nutrition
what is a scar formed form?
collagen and matrix materials
what’s the difference between scard skin and normal skin?
vessels than normal skin
Lack of hair, sensory neurones or skin glands
whats keloid scaring?
Scar extends past the original wound and into surrounding tissues
More common in darker skins
whats hypertrophic scarring?
Raised scar
Remains within original wound boundary
what cells does skin cancer involve?
squamous cell, basal cell, melanocyte
what skin disorder is Psoriasis?
very rapid skin cell turnover
cells build up on the skin
forms thick, flaky patches called plaques
what does eczema cause?
intense itching
inflammation occurs
