M1 L1 Flashcards
Largest and most visible organ in the body
Skin
what % of body weight is skin?
16%
what surface area does skin occupy?
1.5-2 m^2
What evolutionary features make us unique and why?
- “Bare and sweaty” skin
- Less body hair therefore more sweat glands for more effective cooling. Since we evolved for hunting and moving.
skin performs (complex/simple) roles in the body?
complex
Pranksters Easily Make Ketchup Stains Last Decades
functions of skin and accessory structures
- protection
- Excretion
-Maintanence
-melanin
-keratin
-synthesis vitD
-lipids
-detect
What basic tissue types are skin made of?
Composite organ therefore all 4 basic tissue types.
- epithelial
- connective
- muscle
- nervous
3 Layers of the skin
- Epidermis (cutaneous)
- Dermis (cutaneous)
- Hypodermis (subcutaneous)
Epidermis
- stratified barrier
- mostly keratinocytes
- Avascular (no blood circulation)
How does the epidermis get nutrients?
From blood vessels from the dermis layer
what basic tissue is the epidermis mainly made up of?
epithelial tissue
(stratified squamous epithelium) - acting as a barrier
3 different types of epithelia
Simple (single layer of) or Stratified (stacks of)
- squamous (flattened)
- cuboidal
- columnar
Come Get Some Burgers
Epidermis layer for thin skin (from external down)
- stratum corneum (squamous)
- stratum granulosum (squamous)
- stratum spinosum (cuboidal)
- stratum basale (columnar)
Come Lets Get Some Burgers
Epidermis layer for thick skin (from external down)
- stratum corneum (squamous)
- stratum lucidum
- stratum granulosum (squamous)
- stratum spinosum (cuboidal)
- stratum basale (columnar)
only difference is stratum lucidum is present in thick skin
examples and features of thick skin
- e.g. palms of hands, soles of feet
- no hair is present
- has an additional epithelial layer (stratum lucidum)
spiky layer
Stratum Corneum
- dead, dried out, hard cells
- no nuclei
- easily flakes off
granular layer
Stratum Granulosum
Has granules to promote
- dehydration of cell
- cross-linking of keratin fibres
Waxy material secreted into intercellular space
spinous or prickly cell layer
Stratum Spinosum
- Desmosomes anchor neighbouring cells WITHIN the epidermis.
- cuboidal
basal layer
Stratum Basale
- regenerative stem cells
- As it divides, the daughter cell replenishes the layer above.
Basement Membrane
- made of hemidesmosome
- anchors stratum basale (of epidermis) to dermis
Stratum Lucidum
- only in thick skin
- dead cells
layer(s) of epidermis that are dead in thin skin
Only Stratum corneum
layer(s) of epidermis that are dead in thick skin
stratum corneum
stratum lucidum
Dermis
- protein fibres for strength and toughness (collagen and elastin)
- vascular for nourishment
- not shed
what anchors the dermis to epidermis
hemidesmosomes
layers of dermis (from external to in)
- papillary
- reticular
Papillary layer of dermis
- outer layer
- highly vascularised tissues
Reticular layer of dermis
- collagen and elastin “mesh-like” structure for strength
Similarities of both layers of the dermis
blood vessels
lymphatics
sensory nerve fibres
accessory structures
what is a plexus
network of blood vessels OR nerves
2 types of plexuses of the dermis
- cutaneous plexus
- sub-papillary plexus
Cutaneous Plexus
- network of blood vessels present at the very bottom of reticular dermis layer (at junction b/w dermis and hypodermis)
- supplies nutrients to hypodermis and the deeper dermis
Sub-Papillary Plexus
- branches from cutaneous layer (epidermis + dermis)
- lies deep to papillary layer (of dermis)
- provides nutrients and O2 to upper dermis and epidermis
Hypodermis
-Adipose tissue
- subcutaneous layer
functions of hypodermis
The subcutaneous fat…
- stores energy
- gives insulation
Site of injections (hypodermic needles)
1st degree burns
- superficial (only outer layer of epidermis)
- red/pink (erythema), dry and painful
- no blisters
- skin retains function of repelling water and pathogens
- 3-10 days healing
- e.g. mild sunburn
Two types of 2nd degree burns
normal and deeper
normal 2nd degrees
- affects epidermis + parts of dermis
- painful, moist, red and blistered
- heals in 1-2 weeks (with good dressing)
deeper 2nd degrees
- can include whiteish, waxy looking areas
- hair follicles and sweat glands may stay in tact
- heals in ~ 1 month
- loss of sensation and scarring
3rd degree burns
full thickness burns
- even extends into subcutaneous tissue (and maybe involving muscle and bone)
- varied colour (waxy white to deep red to black)
- Hard, dry & leathery skin
- No pain (bc nerve endings are destroyed)
- may require skin grafting (one piece of skin transplanted from one area to another)
- weeks to regenerate + scarring
