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Chapter 18 Skin, Digestion, Excretion, Endocrine Name ________________________ Life Science Period ______ 1. Homeostasis – When your organs work together to maintain a stable environment in the body this is called homeostasis. 2. Integumentary System – The body system that consists of the skin, hair, and nails is called the integumentary system. It protects all the tissues that lie beneath it. The skin is the first line of defense against moisture and invading organisms like bacteria. Because skin covers the entire body it is considered the largest organ of the body. (394) 3. Sweat Glands – Glands in the skin produce a salty fluid called sweat. These glands are called sweat glands. Sweating helps regulate body temperature and excretes (gets rid) of wastes. There are about 3 million sweat glands in the skin. Sweat contains water, salt and a waste called urea. When sweat evaporates off the skin it cools the skin, as well as the blood underneath. As stated before this helps us control body temperature. (394) 4. Epidermis & Dermis – The thin outer layer of the skin is called the epidermis. Hair follicles are found in the epidermis of your skin, as well as muscle fibers that help the hairs stand up. This helps regulate body temperature. The dermis layer lies underneath and is made from connective tissue and protein fibers. The dermis contains the sweat glands and the nerve endings. The dermis also contains the oil glands that produce oils to waterproof your skin. Underneath the skin is a third subcutaneous fat layer that functions as insulation for the body. (394) Note: Small amounts of vitamin D are produced in the epidermis when it is exposed to sunlight. This is important to our overall health. Also, there are many dead cells on the surface of the epidermis. Many of these dead cells are continually rubbing off, causing the flaking and renewal of your skin. 5. Melanin – Pigment cells in the epidermis produce a chemical called melanin that darkens the skin (tan). Melanin protects the skin from the harmful ultraviolet light of the sun. 6. Endocrine System & Hormones – A group of ductless glands produce chemicals called hormones and release them into the blood. These glands are called endocrine glands and they make up the endocrine system. A hormone is a chemical that regulates body functions such as cell processes, reproduction, or response to stress. (395) 7. Pituitary Gland – The master gland of the endocrine system is called the pituitary gland. It is found at the base of the cerebrum (brain) and it produces hormones that control all the other glands. It is the gland that also controls body growth. (395) 8. Adrenal Glands – The adrenal glands produce a hormone called epinephrine, which is sometimes referred to as adrenaline. Epinephrine (adrenaline) prepares several of your organs for stress. It is your “fight or flight” hormone. It increases heart rate, breathing rate, and the release of additional blood sugar for extra energy. The adrenal glands also help control blood sugar, salt and water balance, and cell metabolism. (395) 9. Thyroid & Parathyroid Gland – The thyroid gland in the throat makes a hormone which controls how quickly energy is produced in the body. It does this by controlling the use of carbohydrates (sugar) and, therefore, the level of cellular energy. The parathyroid glands in the throat control the level of calcium in the blood. 10. Pancreas – The pancreas releases a hormone called insulin. Insulin helps regulate the amount of dissolved sugar in the blood. Insulin works with the liver in the storage and release of blood sugar (glucose). The pancreas also produces enzymes that help the digestive system digest carbohydrates, proteins, and fats. (395) 11. Testes & Ovaries – Endocrine glands that produce sex cells, and hormones to regulate the development of male and female traits, are called the testes (male, produce the hormone testosterone), and the ovaries (female, produce hormones progesterone and estrogen). (395) 12. Feedback Control Systems – Systems that control the level of endocrine hormones in the blood are called feedback control systems. Example: The pancreas releases insulin to control high levels of blood sugar that enter from the digestive system. Insulin tells the liver to store the extra blood sugar. This brings sugar levels back to normal and the pancreas then stops producing insulin. When the pancreas does not produce insulin properly this causes a malfunction to the feedback system called diabetes. (396) 13. Digestive System – A groups of organs that take in food, digest it so that it can be absorbed into the blood, and then eliminate the solid waste that is left over is called the digestive system. Digestion starts in the mouth. (chewing, saliva). It then moves down the esophagus to the stomach. There gastric juice (acid) is added for digestion. It liquefies the food. Mucous is also added to protect the stomach from the acid . Next food moves into the small intestine. Here bile from the liver is added (to break up fat) and digestive enzymes from the pancreas are added. The pancreas also adds bicarbonate to neutralize the stomach acid. Most of the digestion and absorption of food into the blood occurs through the villi (finger-like projections) in the small intestine. Water and undigested wastes then move into the large intestine. The water and vitamins are absorbed there. Solid waste is then eliminated through the rectum and out the anus. (397) Note: The liver often produces extra bile. This is stored in an organ called the gall bladder. 14. Excretory System – A group of organs that excrete (remove) chemical wastes are called the excretory system. The liver breaks down waste compounds into urea. Urea is a by-product left over after protein reactions in the body. The kidneys and sweat glands in your skin excrete the urea, water, & salts. The lungs excrete carbon dioxide, which is a waste product left over after your cells break down sugar for energy. (397) 15. Testes – The male reproductive glands are called the testes. They produce sperm and the hormone called testosterone. This regulates the development of male traits and the production of sperm. (398) 16. Ovaries – The ovaries are the female glands of the reproductive system. They produce female hormones called estrogen and progesterone. They regulate the development of female traits, and the production and release of eggs. (398)