Layers of the Skin Flashcards
What is skin?
The largest and most visible organ of the body
- 16% of body weight
- 1.5-2m^2 of surface area
Bare sweaty skin makes us unique, evolved from needing more efficient cooling mechanism due to hunting, running etc.
What are some of the general functions of the skin?
Protection, producing keratin, producing melanin, lipid storage, detecting touch (sensory receptors)
What tissue is the skin made out of?
All 4 tissue types (epithelial, connective, muscle and nervous)
What are the 3 primary layers of the skin?
Epidermis
Dermis
Hypodermis
What is the epidermis?
Outermost layer of the skin
Stratified squamous (multiple layer, flat) barrier
Mostly keratinocytes (cells that contain lots of keratin)
No blood circulation (avascular)
What is the dermis?
Middle layer
Protein fibres for strength - holds everything together
Proteins include collagen and elastin
Vascular (nourishes itself and epidermis)
What layers make up the cutaneous?
Epidermis and Dermis
What is the hypodermis?
Layer below dermis/innermost layer of skin
Consists mostly of adipose tissue (subcutaneous fat producing cells)
Subcutaneous fat stores energy and provides insulation
Common site of injections using hypodermic needles
What layer makes up the subcutaneous?
Hypodermis
What tissue type dominates the epidermis?
Epithelial tissue as it is the tissue that covers exposed surfaces and forms secretory glands
What are the two types of epithelia and what are the three ways they can be arranged?
Simple epithelia meaning ‘single’ layer
Stratified epithelia meaning ‘stacked’ layer
Squamous (flat), cubodial (cube) and columnar (tall columns)
What are the four layers in regards to THIN skin?
Stratum Corneum (spiky layer)
Stratum Granulosum (granular layer)
Stratum Spinosum (spinous layer)
Stratum Basale (basal layer)
Come Get Some Bagels (corneum, granulosum, spinosum, basale)
What are the five layers in regards to THICK skin?
Stratum Corneum (spiky layer)
Stratum lucidum (transparent layer)
Stratum Granulosum (granular layer)
Stratum Spinosum (spinous layer)
Stratum Basale (basal layer)
Come Let’s Get Some Bagels (corneum, lucidum, granulosum, spinosum, basale)
What is the stratum corneum?
Spiky layer of dead dried out hard cells without nuclei, easily flakes off and can be completely removed
What is the stratum lucidum?
Dead, transparent, extra layer for thick skin
What is the stratum granulosum?
Granular layer that contains granules that promote dehydration of the cell, crosslinking of keratin fibres
Waxy material is secreted into the intracellular spaces (fills gaps in between granules)
What is the stratum spinosum?
Spinous layer made up of desmosomes that link the cells together which are increasingly flattened as they move upward
What is the stratum basale?
Basal layer made up of columnar regenerative cells (stem cells)
As the basal cell divides, a daughter cell migrates upwards to replenish the layer above, pushed up the layers until they flake off
What is the basal membrane?
Membrane that is found at the bottom of the epidermis and is shared with the dermis
What are desmosomes?
Cells that anchor adjacent/neighbouring cells in the epidermis
What are hemidesmosomes?
Cells that anchor stratum basale to the dermis
What are some properties of thick skin?
Has 5 layer, found in palms of hands and soles of feet, no hair, extra epidermal layer for durability
What is the dermal papilla?
Provides epidermis with nutrients and blood received from papillary layer
Where is the dermis situated?
It is situated below the epidermis and anchors via hemidesmosomes
Not shed
Divided into two layers : papillary and reticular
What is the papillary layer?
Layer consisting of highly vascularised tissues for nourishment
Supplies blood to epidermis and dermis
What is the reticular layer?
‘Mesh like’ structure of collagen and elastin fibres (for strength), contains blood vessels
What is the cutaneous plexus?
Network of blood vessels present in between the dermis/hypodermis
Supplies nutrients to hypodermis, deeper dermis, capillaries for hair follicles and sweat glands
What is the subpapillary plexus?
Branches from the cutraneous plexus
Lies deep to papillary layer of dermis
Network of blood vessels providing oxygen and nutrients to the upper dermis and epidermis
What is a first degree burn?
Superficial (only involves the outer layers of the epidermis)
Red/pink, dry, painful (erythema)
Usually no blisters e.g. mild sunburn
Skin remains a water and bacterial barrier (can still perform functions)
Usually heals 3-10 days
What is a second degree burn?
Normally: epidermis and varying amounts of dermis affected, painful, moist, red and blistered, heals in approx 1-2 weeks
Deeper: whiteish wax looking areas, hair follicles & sweat glands may stay intact, heals in 1 month, may have loss of sensation and scarring
What is a third degree burn?
Extends into the subcutaneous tissue (full thickness burn), may involve muscle and bone
Varied colour from waxy white through to deep red or black
Hard, dry and leathery skin
No pain in these areas as sensory nerve endings are destroyed
May require skin graft, weeks to regenerate and scarring
