April 12, 2018 Journal: Explain two differences between viruses and bacteria. HAND IN YOUR JOURNALS AFTER YOU FINISH TODAYS!

Integumentary System

Functions: Protection Keeps the body from drying out Stores fat Produces vitamin D Sensory input Regulates body temperature

Skin Made up of 3 tissue layers: Epidermis Dermis Subcutaneous fascia a.k.a. hypodermis

Epidermis Outermost layer of skin Made up stratified squamous epithelial tissue Contains no blood vessels or nerve cells

Layers of the Epidermis

Stratum corneum Dead cells on the outermost surface of the skin that are shed Flat, scaly, and keratinized epithelial cells Protect the layers underneath from drying out

Stratum lucidum Layer of dead, keratinized epithelial cells only found in parts of the body with thick skin Ex: Palms and heels Functions in protection from UV rays

Stratum granulosum Middle layer of the epidermis where living cells are filled with keratin and begin to die

Stratum spinosum Living epithelial cells that do not receive nutrients from the dermis, but divide at a slow rate Contain Langerhans cells that aid in the immune response

Stratum basale Living epithelial cells that receive nutrients from the dermis Undergo rapid mitosis to replace lost cells Contains melanocytes

Melanocytes Produce melanin, the substance that is responsible for your skin color More melanin = darker skin color

Epidermis Layer Shedding Surface cells are constantly shedding Cells originate in the stratum basale and are pushed upward towards the surface As they are pushed upwards the cells die and become filled with a protein called keratin This process takes between 2 and 4 weeks

Dermis Layer right below the epidermis Thick layer of irregular connective tissue

Two Layers within the Dermis: Both contain collagen and elastic fibers Papillary Layer Top layer of thin fibers Contains ridges that are responsible for fingerprints Reticular Layer Bottom layer of thick fibers

Collagenous and elastic fibers Helps your skin shift when you move Allows skin to return to its normal shape when your body is at rest Stretches out over time so skin loses it’s firmness and flexibility

Subcutaneous fascia Aka hypodermis Innermost layer of skin Composed of fatty tissues and elastic and fibrous connective tissue Connects to the muscles of your body

Lipocytes Fat cells produce the fat needed to protect the body and to act as insulation for regulating temperature