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Integumentary Integumentary
System System –– Skin Skin
LayersLayers
Divisions of the Integumentary Divisions of the Integumentary
SystemSystem
�� The integumentary system is composed of the The integumentary system is composed of the
skin and it’s accessory organs.skin and it’s accessory organs.
�� The skin has three distinct layers.The skin has three distinct layers.
�� EpidermisEpidermis
�� DermisDermis
�� Subcutaneous fat or hypodermis.Subcutaneous fat or hypodermis.
Divisions of the Integumentary Divisions of the Integumentary
SystemSystem
�� Accessory organs.Accessory organs.
�� Hair, Nails, and Glands (sweat and oil).Hair, Nails, and Glands (sweat and oil).
�� All of the accessory organs are based and formed All of the accessory organs are based and formed
from epidermis, although they are located in the from epidermis, although they are located in the
dermis.dermis.
General FactsGeneral Facts
�� The skin has a surface area of between 1.5 and The skin has a surface area of between 1.5 and
2.0 square meters.2.0 square meters.
�� The skin weighs 4The skin weighs 4--5 kg (95 kg (9--11 lbs).11 lbs).
�� Each cmEach cm22 of skin contains:of skin contains:
�� 70cm of blood vessels.70cm of blood vessels.
�� 55cm of nerves55cm of nerves
�� 100 sweat glands100 sweat glands
�� 15 oil glands15 oil glands
�� 230 sensory receptors.230 sensory receptors.
Skin Structure page Skin Structure page 153 (This is on 153 (This is on pg 4 of notes pg 4 of notes –– You need know all You need know all
of your diagrams!of your diagrams!
Figure 4.4
Begin pgs 5Begin pgs 5--6 of notes6 of notes
Look at diagrams carefully to see Look at diagrams carefully to see
which layer the information is which layer the information is
referring to. Remember: Structure referring to. Remember: Structure
determines Function!determines Function!
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Epidermis Epidermis –– page 6 of notes page 6 of notes -- fill in fill in
text box on left side of diagramtext box on left side of diagram
Slide Slide
4.10a4.10a
• Epidermis – outer layer – color code brackets
• Thick keratinized stratified squamous epithelium (4 or 5 layers)
• Avascular (hardened by keratin)
• Renews itself ~ every 35 - 45 days
• Has 4 distinct cell types
• Need to know this slide!
Dust Mites Dust Mites –– eat your dead eat your dead
keratinocyteskeratinocytes
Epidermis Epidermis –– cell cell types types –– Go to page 5 Go to page 5
of notes & fill in cell info (upper right)of notes & fill in cell info (upper right)• Keratinocytes
• Makes ups majority of epidermal cells
• produce keratin – waterproofing protein•Why important? To keep you from gaining/losing water
• Originate in deeper layers & get pushed to surface – becomes keratin filled & dies
• Reminder: Connected to each other by desmosomes & tight junctions
• Cell production & keratinization are accelerated in areas of friction
•Callus – thickened skin for protection
Epidermis Epidermis –– cell cell types types –– pg 5pg 5• Melanocytes
• Found in the stratum basale • Produce melanin (gives us skin color)
which accumulates on superficial
(between nucleus & sun) side of nucleus
• Why that location? to prevent DNA
mutation from the UV radiation
Mutation can change growth
instructions & cause cancer
MelanocytesMelanocytes
•• All people have ~ the same number of All people have ~ the same number of
melanocytesmelanocytes..
•• Skin coloring differences are due to Skin coloring differences are due to
melanocytemelanocyte activity, or the rate of melanin activity, or the rate of melanin
catabolism within catabolism within keratinocyteskeratinocytes
3
Epidermal CellsEpidermal Cells
�� Langerhans’ cells are formed in the bone Langerhans’ cells are formed in the bone
marrow and migrate to the epidermis.marrow and migrate to the epidermis.
�� These starThese star--shaped cells are macrophage that shaped cells are macrophage that
help to activate the immune system.help to activate the immune system.
�� Macrophage are cells that phagocytize foreign Macrophage are cells that phagocytize foreign
materials (like pacmaterials (like pac--man).man).
Epidermal CellsEpidermal Cells
�� Merkel Cells. These cells are found at the Merkel Cells. These cells are found at the
epidermal/dermal junction and are associated epidermal/dermal junction and are associated
with sensory nerve endings. The combination with sensory nerve endings. The combination
of a merkel cell and a nerve ending is called a of a merkel cell and a nerve ending is called a
Merkel disc, and act as a sensory receptor for Merkel disc, and act as a sensory receptor for
touch.touch.
Label the 5 strata on page 5 left Label the 5 strata on page 5 left
sideside
5 5 epidermal strata (layers)epidermal strata (layers)––
place info on page 5 right sideplace info on page 5 right side
• From DEEP TO SUPERFICIALDEEP TO SUPERFICIALDEEP TO SUPERFICIALDEEP TO SUPERFICIAL
• Stratum basale• Most important layer• highly mitotic• Approx. 25% melanocytes• Attached to dermis along a wavy border
•• Stratum Stratum spinosumspinosum
•• WebWeb--like system of filaments made of bundles like system of filaments made of bundles of keratinof keratin
•• Several layers thickSeveral layers thick
•• Slightly mitoticSlightly mitotic
•• Contains Contains Langerhan’sLangerhan’s macrophagesmacrophages
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5 strata of the Epidermis5 strata of the Epidermis
• Stratum granulosum
•3-5 cell layers thick
•Keratinocytes flatten & lose organelles
•Also contains Langerhans cell
•contains keratin granules-major factor in slowing water loss from epidermis
•• Stratum Stratum lucidumlucidum
•• found in thicker epidermis found in thicker epidermis –– palms, palms, soles, callussoles, callus
•• Few rows of clear, flattened, DEAD Few rows of clear, flattened, DEAD keartinocyteskeartinocytes
5 strata of the Epidermis5 strata of the Epidermis• Stratum corneum
• Also completely keratinized (& dead)
• Outer most layer 20-30 cells thick
• Accounts for ¾ of the epidermal thickness
• Tough (protects from abrasions & penetration), also waterproofing protection
• AGAIN: Why is waterproofing important?
• Average people shed 18 kg (40 lbs) in a lifetime
How it all fits togetherHow it all fits together
Dermis Dermis –– back to page 6back to page 6
• Left side: Strong, flexible CT - 2 layers
• Semi-fluid matrix with many collagen, elastin, & reticular fibers
• Cells found in dermis:
• Fibroblast – form connective fibers
• Macrophage – phagocytic cells
• Mast cells – immune cells, detect foreign material
• White blood cells – immune cells
•• Right side Right side -- Papillary dermisPapillary dermis
•• Contains Contains areolarareolar CTCT
•• Dermal papillae Dermal papillae –– indent into the indent into the epidermis epidermis –– form fingerprintsform fingerprints
•• What else is important about these? What else is important about these? Give us grip !Give us grip !
•• Also contain Also contain
�� nerve receptors,nerve receptors,
�� Lots of blood vesselsLots of blood vessels
Dermis Dermis –– back to page 6back to page 6
5
Blister: add in margin pg 6Blister: add in margin pg 6
�� Dermal Dermal –– epidermal junctionepidermal junction
�� Held together by Held together by desmosomesdesmosomes
�� Blister Blister -- separation due to mechanical stressseparation due to mechanical stress
�� What What 2 2 sublayerssublayers actually separateactually separate? Think about this!!? Think about this!!
DermisDermis
• Page 6 - right side
• Reticular Dermis – 80% of dermis
• Reticular CT & Dense irregular CT – also contains Blood vessels, Nerve receptors, Glands
• cleavage lines – direction of fibers in collagen bundles – used in plastic surgery to reduce scarring
• flexure lines – dermis secured to hypodermis
• Obvious dermal folds located around the joints that allow skin to fold when joints move
• stretch marks – dermal tears
Cleavage linesCleavage lines DermisDermis
Hypodermis Hypodermis –– pg 6 left sidepg 6 left side
Slide Slide
4.10b4.10b
• Deep to dermis is the hypodermis -superficial fascia
• Anchors skin to underlying organs, shock absorption, insulation
• Composed mostly of adipose tissue
• Very vascular
• Site of subcutaneous injections
5 Tissues5 Tissues
�� There have been 5 types of tissues during the There have been 5 types of tissues during the
previous slidesprevious slides
�� Find the 5 types & write them in the margin on Find the 5 types & write them in the margin on
page 6: You will need to MEMORIZE the page 6: You will need to MEMORIZE the
location/function/slide of these 5 for this unit location/function/slide of these 5 for this unit
testtest