The integumentary system is composed of the skin and it’s accessory organs. The skin has three distinct layers.
Divisions of the Integumentary System
Accessory organs.
General Facts
Hair, Nails, and Glands (sweat and oil). All of the accessory organs are based and formed from epidermis, although they are located in the dermis.
Epidermis Dermis Subcutaneous fat or hypodermis.
The skin has a surface area of between 1.5 and 2.0 square meters. The skin weighs 44-5 kg (9(9-11 lbs). Each cm2 of skin contains:
70cm of blood vessels. 55cm of nerves 100 sweat glands 15 oil glands 230 sensory receptors.
Skin Structure page 153 (This is on pg 4 of notes – You need know all of your diagrams!
Begin pgs 55-6 of notes Look at diagrams carefully to see which layer the information is referring to. Remember: Structure determines Function! Figure 4.4
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Epidermis – page 6 of notes - fill in text box on left side of diagram
Dust Mites – eat your dead keratinocytes
• 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! Slide 4.10a
Epidermis – cell types – Go to page 5 of notes & fill in cell info (upper right) • Keratinocytes
Epidermis – cell types – pg 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
• 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
Mutation can change growth instructions & cause cancer
Melanocytes •
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All people have ~ the same number of melanocytes.. melanocytes Skin coloring differences are due to melanocyte activity, or the rate of melanin catabolism within keratinocytes
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Epidermal Cells
Langerhans’ cells are formed in the bone marrow and migrate to the epidermis. These starstar-shaped cells are macrophage that help to activate the immune system.
Epidermal Cells
Macrophage are cells that phagocytize foreign materials (like pacpac-man).
Merkel Cells. These cells are found at the epidermal/dermal junction and are associated with sensory nerve endings. The combination of a merkel cell and a nerve ending is called a Merkel disc, and act as a sensory receptor for touch.
Label the 5 strata on page 5 left side
5 epidermal strata (layers)– (layers)– place info on page 5 right side • From DEEP TO SUPERFICIAL • Stratum basale • Most important layer • highly mitotic • Approx. 25% melanocytes • Attached to dermis along a wavy border
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Stratum spinosum • Web Web--like system of filaments made of bundles of keratin • Several layers thick • Slightly mitotic • Contains Langerhan’s macrophages
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5 strata of the Epidermis • Stratum granulosum •3-5 cell layers thick
•contains keratin granules-major factor in slowing water loss from epidermis
found in thicker epidermis – palms, soles, callus Few rows of clear, flattened, DEAD keartinocytes
5 strata of the Epidermis
How it all fits together
• 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
Dermis – back 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
Dermis – back to page 6 •
Right side - Papillary dermis •
Contains areolar CT
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Dermal papillae – indent into the epidermis – form fingerprints •
What else is important about these? Give us grip !
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Also contain
nerve receptors,
Lots of blood vessels
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Dermis
Blister: add in margin pg 6
Dermal – epidermal junction
Held together by desmosomes Blister - separation due to mechanical stress
What 2 sublayers actually separate? separate? Think about this!!
Cleavage lines
• 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
Dermis
Hypodermis – pg 6 left side
5 Tissues
• Deep to dermis is the hypodermis -
superficial fascia
• Anchors skin to underlying organs, shock absorption, insulation
• Composed mostly of adipose tissue • Very vascular
There have been 5 types of tissues during the previous slides Find the 5 types & write them in the margin on page 6: You will need to MEMORIZE the location/function/slide of these 5 for this unit test
