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The Circulatory System

Life Science - Middle School

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The Circulatory System © C opyright NewPath Learning. All Rights Reserved. 94-4904 www.newpathlearning.com The circulatory system is made up of the heart, blood vessels, and blood. The circulatory system moves nutrients, gases and wastes to and from of the cells by the pumping action of the heart. It also helps to ﬁ ght disease and infections and helps to maintain a constant body temperature. The Heart The most important structure of the circulatory system is the heart. The heart is a hollow muscle made of cardiac muscle that pumps blood to all the cells in the body. It lies underneath the breastbone and is protected by the rib cage. There are two loops in the circulatory system. The blood ﬂ ows from the heart to the lungs and back to the heart in the ﬁ rst loop. The blood ﬂ ows from the heart, out to the body, and back to the heart in the second loop. Blood takes less than a minute to travel through both loops. During the ﬁ rst loop, the blood leaves the right atrium, then is pumped out of the right ventricle to the lungs. This is where blood picks up oxygen and drops off carbon dioxide and other wastes. The blood then returns to the heart. During the second loop, the blood leaves the left atrium, then is pumped out of the left ventricle through the aorta, to all of the cells in the body. The blood drops off oxygen to the cells and picks up carbon dioxide and other wastes. Blood Vessels The arteries are blood vessels that move blood away from the heart and on to the rest of the body. Capillaries are small blood vessels that connect the arteries to the veins and are where substances are exchanged. The veins are blood vessels that carry blood loaded with wastes back to the heart. A B AB O Blood Groups The main blood groups are A, AB, B, and O. The blood type of a person is determined by the presence or absence of antigens (markers) found on the surface of red blood cells. The markers also determine the type of blood you can safely receive in a blood transfusion. What is blood made of? If you were to place whole blood into a test tube and spin it, it would separate into three layers. The top layer would be the liquid part of the blood called plasma. The second layer would consist of white blood cells and platelets and the last layer would be the red blood cells. Plasma is made mostly of water and contains dissolved nutrients, vitamins, minerals and carries wastes from the cells. plasma white blood cells platelets red blood cells whole blood white blood cells red blood cells platelets The Lymphatic System Blood will occasionally leak out through the walls of the blood vessels. The liquid is brought back to the bloodstream by a network of vein-like vessels called the lymphatic system. Once the ﬂ uid is within the lymphatic system it is called lymph. Lymph is put back into the veins through lymphatic vessels. As the liquid passes through the lymphatic system, it enters structures called lymph nodes. Red blood cells are made of a protein that binds together with oxygen molecules called hemoglobin. White blood cells are the disease ﬁ ghters of the body. Platelets are fragments of cells that are critical to forming blood clots to prevent bleeding. lymph node 1st loop lungs body organs body trunk and limbs 2nd loop aorta left atrium left ventricle right right atrium atrium right ventricle pulmonary artery artery vein capillaries valves lymph vessels lymph vessels Veins have valves which allow the blood to ﬂ ow in one direction and prevent it from ﬂ owing backwards. antigens mitral valve tricuspid valve

The Circulatory System © C opyright NewPath Learning. All Rights Reserved. 94-4904 www.newpathlearning.com \xiBAHBDy01778tz] 1st loop 2nd loop What is the function of the circulatory system ? _____________________________________________ _____________________________________________ Describe the blood flow in the circulatory system. _____________________________________________ _____________________________________________ _____________________________________________ The Heart What is the function of the heart ? _______________________________________ _______________________________________ _______________________________________ Blood Vessels Arteries are ___________________________. Capillaries are _________________________. Veins are ______________________________. The Lymphatic System What is the function of the lymphatic system ? _____________________________________________ _____________________________________________ _____________________________________________ What is blood made of? Whole blood is made up of ____________________ _____________________________________________ _____________________________________________. Describe the following: Red blood cells __________________________ White blood cells ________________________ Platelets _______________________________ A B AB O Blood Groups What are the four main blood groups? • aorta • mitral valve • antigen • plasma • artery • platelet • blood • red blood cell • capillary • right atrium • heart • right ventricle • left atrium • tricuspid valve • left ventricle • valve • lymph node • vein • lymph vessel • white blood cell Key Vocabulary Terms

The Circulatory System

Life Science - Middle School

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