Integumentary System Protecting you from the outside world

Parts of the system Skin ◦ Layers- dermis, epidermis Hair follicles Nails Sweat Glands Sebaceous Glands *Some consider other membranes as well (ex- mucosal). We will only look at skin

Skin 2 layers ◦ Epidermis ◦ Dermis Epidermis ◦ Dead, keratinized skin, made of 5 layers of dead skin ◦ Constantly shed ◦ Holds melanocytes, make melanin, skin pigment Dermis ◦ Under epidermis ◦ Made of blood vessels, connective tissue

Epidermis Mainly dead, keratinized cells Melanocytes ◦ Cells producing melanin- a dark pigment ◦ Dark pigment absorbs UV B rays, preventing them from damaging DNA in cells below ◦ Melanocytes increase melanin production with increased exposure to UV light.   TAN

Within the skin Hair follicles Sweat Glands Sebaceous Glands

Hair Follicles Cells within dermis divide by mitosis ◦ As cells push up, keratinization occurs (like epidermis) ◦ Type of keratin (genetically determined) results in hair’s shape (straight, curly, etc.) Goosebumps ◦ Small muscle pulls on hair, causing to stand on end ◦ Evolutionary reaction to trap heat

Sweat Glands Small tubes beginning in dermal layer Tube exits on epidermis through pore ◦ Excretion contains  Salt  Urea  Uric acid  Ammonia  Sugar ◦ As water evaporates, removes heat from body

Sebaceous Glands Along sides of hair follicles Create oily substance that rubs onto hair and skin Increase production during puberty,  acne!

Nails Also keratinized As keratin and air mix, white substance is left on nail nearest skin Nail bed grows nails1mm per week

Real Life Application Hair Straightening ◦ Keratin in hair has many disulphide bonds in its amino acid chains  Makes hair VERY stable ◦ HEAT breaks disulphide bonds, allowing you to put hair in a different position  Moisture allows disulphide bonds to reform ◦ Perms-  Bonds broken by strong bases, then acid added to neutralize chemicals and allow disulphide bonds to reform in new ways

Real Life Application Lasers prevent hair growth ◦ Laser hair removal uses strong, concentrated laser beam to aim at hair ◦ Pigment in hair absorbs beam, damages hair follicle enough to prevent hair growth