Integumentary System Andrew Lopez Julie Nguyen Ethan Schwartz Period 3
A. The Epidermis • The epidermis is the outermost layer of the skin and serves as protection from almost anything, such as heat, water, bacteria, etc. • The word epidermis comes from the Greek words “epi” meaning above and “derma” meaning skin. • The epidermis mainly consists of the cells keratinocytes. • Keratinocytes produce a fibrous protein forming the main structural parts of hair, feathers, hoofs, claws, horns, etc.
B. The Dermis • The dermis is the middle layer of the skin and contains some hair follicles and sweat glands as well as lymph nodes and blood vessels. • The main function of the dermis is to preserve the body heat and to also provide firmness. • The dermis has two layers: • Papillary layer: Consists of loose connective tissue with collagen and elastic fibers. Contains receptors for touch and pain. • Reticular layer: Contains collagen and elastic fiber that allows the skin to stretch and then return to its original shape.
C. The Cutaneous Glands • The cutaneous glands are all exocrine glands that hide on the surface of the skin by means of ducts. • There are two main types of glands: sebaceous (oil) glands and sudoriferous (sweat) glands. • Oil glands: Found all over the body except on the palms of the hands and the soles of the feet. Mostly opens in the hair follicles. Secretes an oily substance called sebum. • Sebum: A lubricant for the skin and hair and helps to keep the skin from drying up. • Contains anti-bacterial chemicals, which prevents bacteria from invading deeper surfaces of the skin.
Sweat glands: Contains four types of glands: eccrine glands, apocrine glands, ceruminous glands, and mammary glands. • Eccrine glands: Produces sweat in coiled structures located in the dermis, and then dumps it directly on the surface of the skin via pores. Contains mostly water, some salts, lactic acid, vitamin C, and metabolic wastes, like urea and ammonia. Located mainly in the forehead, palms, and soles. • Apocrine glands: Empties contents in the hair follicles. Contains additional fatty acids and proteins. Does not function until puberty. Generally becomes active when someone is emotionally upset or excited. Located in the armpits and public regions. • Ceruminous glands: A modified apocrine glands found in the lining of the outside of the ear canal. Releases a thick, sticky substance called earwax. Blocks the entry of foreign substances with the help of tiny hairs in the ear canal. • Mammary glands: A modified sweat glands used to release milk. During pregnancy, the glandular tissue develops the ability to form milk.
D. Hair and Nails • Hair • The main function is to provide warm insulation. • Has a shaft and a root. The shaft stands out above the surface of the skin, while the root extends below the surface into the dermis, where it is planted in a group of cells called a hair follicle. • Humans have three different types of hair: • Lanugo: Soft, fine hair that covers a fetus around the third or fourth month after conception. • Vellus hair: Soft and fine hair, but grows and persists throughout life, covering most of the body surface. • Terminal hair: Thick and strong, forms the eyebrows and eyelashes, and found on the scalp.
Nails • Modified skin tissues that cover the ends of the fingers and toes. Hardened by the protein keratin. • Lunula is the whitish, crescent moon shaped area at the base of the nail. • Nail bed slides forward over a a layer of epithelium. • The part we trim is the free edge of a nail that extends over the top of a finger or toe. • Cuticles are where the border of a nail overlap with skin folds.
E. The Hypodermis • The hypodermis is the most important layer of skin as it acts as a shock absorber for internal organs and maintains correct internal body heat. • The other layers of skin mainly serve to protect the hypodermis, which cannot be repaired if it is damaged. • A common disease that affects the skin is psoriasis. Psoriasis is the buildup of excess skin which turns red and becomes extremely irritating.
F. Vitamin D • Vitamin D is a fat-soluble vitamin that is produced by the body. • Vitamin D serves many uses for our body; from treating skin conditions, to boosting the immune system, and maintaining proper bone structure. • There are several ways to obtaining Vitamin D, but the most reliable way is exposer to the sun. • Vitamin D is necessary for the body to absorb calcium, and this prevents the bones from becoming thin, brittle, or misshapen. • The process of creating Vitamin D occurs endogenously (from inside of the body) from the liver when the sun’s ultraviolet rays strike the skin, causing the synthesis (or production). • Then Vitamin D is converted into Calcidiol and is then taken to the kidney to be produced as Calcitriol.
G. Skin Conditions & Diseases • A common skin condition is Eczema in which the skin develops a chronic, itchy inflammation. • Speculations are that Eczema is caused by a combination of genetic factors and environmental factors and conditions. • Cortisones, antibiotics, and light therapy are several choices in alleviating the symptoms of Eczema. • Roughly half of children that have had Eczema in the past will have the symptoms continue as adults.
G. How our skin Protects Us • The skin is literally like a force field, repelling any bacteria from entering the body. • Our skin constantly sheds to get off the bacteria that linger on the skin. • Without our skin, chances of infection would be very high and infections would kill us off. • The skin prevents essential body fluids from evaporating (blood, water, lymph). • The skin protects organs and body tissues against physical injuries.
Bibliography • http://www.ivy-rose.co.uk/HumanBody/Skin/Skin_Disorders.php • http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/ • Biology book, pages 863-864 • http://www.ivy-rose.co.uk/HumanBody/Skin/Skin_Disorders.php • Cells, tissues, and Skin by Douglas Light
Quiz 1. What is the correct order of the three layers of the skin? A. dermis, epidermis, hypodermis C. hypodermis, epidermis, dermis B. epidermis, hypodermis, dermis D. epidermis, dermis, hypodermis 2. Which layer of skin contains lymph nodes? A. epidermis C. hypodermis B. dermis D. none of the above 3. Which layer of skin is made of keratinocytes? A. dermis C. epidermis B. hypodermis D. sub-dermis
4. What is the NOT a function of hair? A. Protection from ultraviolet rays C. Shield the eyes. B. Provide warm insulation. D. Provide nutrients to the body 5. What are the two cutaneous glands? A. mammary glands and apocrine glands C. oil glands and apocrine glands B. sweat glands and eccrine glands D. oil glands and sweat glands 6. What is the texture of terminal hair? A. soft, fine hair C. soft, strong hair B. thick, strong hair D. thick, fine hair
7. How does the body usually obtain Vitamin D? A. Through sunlight C. Through sleeping B. From drinking water D. From eating meat 8. What is Vitamin D necessary for? A. Producing saliva C. For promoting muscle strength B. Absorbing calcium D. Creating blood cells 9. What are the main symptoms of Eczema? A. Poor eyesight C. itchy, irritated skin B. Weak bones D. heart palpitations 10. What is the main purpose of the skin? A. To keep our muscles together C. To provide the brain with oxygen B. To prevent infections and diseases D. To open and close our eyelids