The function of the Circulatory system Section 12.1

The purpose of the Circulatory System  Unicellular organisms use diffusion to move nutrients and respiratory gases into the cell and move waste products out.  Multicellular organisms have trillions of specialized cells that need raw materials to survive and produce waste materials that need to be removed.  The circulatory system serves as a transportation system for multicellular organisms.

Main Functions of the Circulatory System  1. It transports gases (from respiratory system), nutrient molecules and waste materials (from digestive system).  2. It regulates internal temperature and transports chemical substances that are vital to health from one part of the body to another.  3. It protects against blood loss from injury and against disease-causing microbes or toxic substances introduced into the body.

Major Components of the Circulatory system  1. The Heart – a muscular organ that pumps the blood through the body and generates blood flow.  2. Blood vessels – A system of hollow tubes through which the blood moves. (the heart and the blood make up the cardiovascular system.)  3. Blood – The fluid that transports nutrients, oxygen, carbon dioxide, and many other materials throughout the body.

Open cardiovascular Systems  Blood flows freely within the body cavity and makes direct contact with the organs and tissues.  Many invertebrates have an open system.  Blood in not separate from interstitial fluid (between cells) and is called hemolymph.  Hemolymph passes though body cavity. It enters the heart through little holes, exchanges nutrients and wastes, and then flows back into body cavity or is removed as waste.

Advantages of an open Circulatory System  Animals are much less vulnerable to pressure. (which is good for mollusks and shellfish that live in water.)  Animals also have more control over their body temperature and can dissipate heat very quickly if they live in a hot environment.

Closed Cardiovascular Systems  Keeps the blood physically contained within vessels and separate from other body tissue.  Blood follows a continuous and fixed path of circulation and is confined to a network of vessels.  Blood is separate from interstitial fluid.  Vertebrates and many other animals have closed systems and it is more efficient than an open system for delivering nutrients to each cell.

Open Vs Closed systems  V82EyeA V82EyeA

Homework  Diary entry – A day in the life of an oxygen molecule  In several short paragraphs, describe the trip that you take when you are inhaled by a human. Explain your trip, beginning rom the air and ending up in a body tissue cell. Explain where you go. What you see, and the emotions you feel throughout the journey.

Review  These are some questions that will help you for Thursday’s quiz.  Digestive system - #1-5, 7-9, P. 435  Respiratory system - #1-2,4,7,9,10, 15 P. 471