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Skin, Hair and Nails
Now using the microscopes. Examine your skin, hair and nails.
In your spiral, diagram what you see.
Organs of the integumentary system
skinhairnails
The name is derived from the Latin integumentum, which means “a covering.”
SkinThe largest organ in your bodyFunctions
Covers the body and prevents water lossProtects the body from injury and infectionRegulates body temperatureEliminates wastes (sweat)Produces vitamin DGathers information about the environmentStores fat for fuel and insulation
Maintains Homeostasis
Helps to keep the body temperature normal
Has blood vessels that tell the body when it is hot or coldHot – blood vessels get larger and sweating
occursCold – blood vessels constrict to keep blood
in the body’s core
Provide Vitamin D
With the help of sunlight, your skin produces vitamin D
Vitamin D is essential in calcium absorption from food
Layers of Skin
Skin consists of three main layersepidermisdermissubcutaneous
layer
subcutaneous layer
Epidermis
Outermost layer30-60 cells thickNo nerves or blood vesselsTop layer is deadNew cells formed at the bottom of this layerSkin cells shed every 2 weeksWhere nails growContains melanin
EpidermisWhere nails growContains melaninEvery minute, 30,000 - 40,000 skin cells fall off95% of your skin cells make new cells5% make melaninMore sun exposure
= more melanin (tan)
Dermis
Middle layerContains nerves and
blood vesselsContains sweat
glands, oil glands and hair follicles
Contains collagen and elastin that allows skin to stretch
subcutaneous layer
Made mostly of fatKeeps you warmAbsorbs shockAttaches your skin
to the underlying tissue
hair
Made of a strong, dead protein, called keratin
Grows out of a tiny tube called a follicle
Hair growth is caused by rapid mitosis in the follicle
Hair follicles are everywhere exceptlipspalmssoles
hair
Over 100,000 follicles on the scalpEach follicle is attached to a gland that
secretes sebum (oil)Color is partially determined by
melanin
nails
Modified hair that grows from your cuticle
Made of keratinNo nerve endingsProtects the end of fingers and toesTakes 6 months to grow from cuticle to
tip
nails
Fingernails grow faster than toenailsNails grow faster on your dominant
handNails DO NOT grow after death