Just as a plumbing system carries water through a series of

37 2 Blood and the Lymphatic System Just as a plumbing system carries water through a series of pipes to different parts of a house, the circulatory system carries blood through a series of blood vessels to different parts of the body. Blood is a type of connective tissue containing both dissolved substances and specialized. Blood collects oxygen from the lungs, nutrients from the digestive tract, and waste products from tissues. Blood helps to regulate factors in the body s internal environment, such as body temperature. In addition, components in blood help to fight infections. Blood can even form clots to repair damaged blood vessels. Blood Plasma The human body contains 4 to 6 liters of blood, which is about 8 percent of the total mass of the body. As Figure 37 7 shows, about 45 percent of the volume of blood consists of, which are suspended in the other 55 percent a straw-colored fluid called plasma. Plasma is about 90 percent water and 10 percent dissolved gases, salts, nutrients, enzymes, hormones, waste products, and proteins called plasma proteins. Plasma proteins, which perform a variety of functions, are divided into three groups: albumins, globulins, and fibrinogen. Albumins and globulins transport substances such as fatty acids, hormones, and vitamins. Albumins also help to regulate osmotic pressure and blood volume. Some globulins fight viral and bacterial infections. Fibrinogen is the protein responsible for the ability of blood to clot. Key Concepts What is the function of each type of blood cell? What is the function of the lymphatic system? Vocabulary plasma hemoglobin lymphocyte platelet lymph Reading Strategy: Asking Questions Before you read, rewrite the headings in the sections as how, why, or what questions about blood and the lymphatic system. As you read, write brief answers to the heading questions. Figure 37 7 Blood consists of plasma, blood, nutrients, hormones, waste products, and plasma proteins. Interpreting Graphics When a whole blood sample is placed in a centrifuge, as shown below, what is the result? Plasma Platelets White blood Red blood 1 FOCUS Objectives 37.2.1 Describe blood plasma. 37.2.2 Explain the functions of red blood, white blood, and platelets. 37.2.3 Describe the role of the lymphatic system. Vocabulary Preview Have students preview new vocabulary by skimming the section and listing the highlighted, boldface terms. They should leave space to make notes as they read the section. Reading Strategy Suggest that students preview section content by studying the figures and reading the captions. They should write down any unfamiliar terms and try to find the meanings as they read. 2 INSTRUCT Blood Plasma Use Community Resources Have students contact their local chapter of the American Red Cross to learn about blood banks and blood drives in their community. Suggest that they try to find out who can and cannot donate blood, how donations are made, and what happens to the donated blood. Urge students to share what they learn with the class. Whole Blood Sample Sample Placed in Centrifuge Blood Sample That Has Been Centrifuged SECTION RESOURCES Print: Teaching Resources, Lesson Plan 37 2, Adapted Section Summary 37 2, Adapted Worksheets 37 2, Section Summary 37 2, Worksheets 37 2, Section Review 37 2 Reading and Study Workbook A, Adapted Reading and Study Workbook B, Investigations in Forensics, Investigation 10 Time Saver Technology: itext, Transparencies Plus, Answer to... Figure 37 7 The cellular portion and the plasma portion of blood separate. Circulatory and Respiratory Systems 951

37 2 (continued) Blood Cells Build Science Skills Calculating Help students appreciate the relative proportions of red and white in blood. Point out that a milliliter of blood contains about 5 million red blood (about 5.2 million in males and about 4.7 million in females) and that red blood outnumber white blood about 1000 to 1. Ask: How many white blood are there in a milliliter of blood? (About 7000) If a milliliter of blood was found to have 20,000 white blood, what might explain this increase? (An infection) Use Community Resources Arrange for interested students to visit a clinic or hospital laboratory where they can observe blood counts being performed. If possible, have a lab technician or supervisor explain why blood counts are performed and what can be learned from them. Other topics the technician or supervisor might address include the importance of accuracy in blood counts and the safety precautions that must be taken when handling blood samples. Have students report to the class on what they learn. NSTA Download a worksheet on blood for students to complete, and find additional teacher support from NSTA SciLinks. (magnification: 2342 ) Figure 37 8 Red blood transport oxygen. White blood fight invasions of foreign substances,, and organisms. Red blood and a single white blood cell are shown in this scanning electron micrograph. NSTA For: Links on blood Visit: www.scilinks.org Web Code: cbn-0372 Blood Cells The cellular portion of blood consists of red blood, white blood, and platelets. Red blood transport oxygen, white blood perform a variety of protective functions, and platelets help in the clotting process. Platelets are actually fragments of derived from larger in bone marrow. Red Blood Cells The most numerous in the blood are the red blood, or erythrocytes (eh-rith-roh-syts). Red blood transport oxygen. They get their color from hemoglobin. Hemoglobin is the iron-containing protein that binds to oxygen in the lungs and transports it to tissues throughout the body where the oxygen is released. Red blood, like those shown in Figure 37 8, are shaped like disks that are thinner in the center than along the edges. These are produced from in red bone marrow. As these gradually become filled with hemoglobin, their nuclei and other organelles are forced out. Thus, mature red blood do not have nuclei. Red blood circulate for an average of 120 days before they are worn out from squeezing through narrow capillaries. Old red blood are destroyed in the liver and spleen. White Blood Cells White blood, or leukocytes (LOOkoh-syts), do not contain hemoglobin. They are much less common than red, which outnumber them almost 1000 to 1. Both white and red blood are produced from the same population of blood-forming stem found in the bone marrow. Unlike red blood, however, white blood contain nuclei. They may live for days, months, or even years. White blood are the army of the circulatory system they guard against infection, fight parasites, and attack bacteria. There are many types of white blood, and they perform a wide variety of important functions. Some protect the body by acting as phagocytes, or eating, that engulf and digest bacteria and other disease-causing microorganisms. Some white blood react to foreign substances by releasing chemicals known as histamines. These chemicals increase blood flow into the affected area, producing redness and swelling that are often associated with allergies. Other white blood, known as lymphocytes, are involved in the immune response. B lymphocytes produce antibodies. Antibodies are essential to fighting infection and help to produce immunity to many diseases. T lymphocytes help fight tumors and viruses. You will learn more about lymphocytes in Chapter 40. White blood are not confined to the circulatory system. Many white blood are able to slip out of capillary walls, travel through the lymphatic system, and attack invading organisms in the tissues of the body. In many ways, white blood are the first lines of defense when the body is invaded by disease-causing organisms. UNIVERSAL ACCESS Inclusion/Special Needs Help students grasp the material on blood by helping them organize the details in a compare/contrast table. Use headings for type of blood cell, number, size, shape, functions, presence/absence of nucleus, source, and life span. Then, call on volunteers to fill in the table with a row for red blood and a row for white blood. Have students save their tables to use as study guides. Advanced Learners Challenge students to find out how hemophilia is inherited and why it occurs primarily in males. Have them focus on hemophilia in the family of Queen Victoria of England. They should find a family tree showing which of Victoria s descendants had the disease or carried the defective gene. Ask volunteers to explain to the class how hemophilia is inherited, using the family tree to illustrate their explanation. 952 Chapter 37

Like an army with units in reserve, the body is able to increase the number of white blood dramatically when a battle is underway. A sudden increase in the white blood cell count is one of the ways in which physicians can tell that the body is fighting a serious infection. Platelets and Blood Clotting Blood is essential to life. An injury can cause the body to lose this essential fluid. Fortunately, blood has an internal mechanism to slow bleeding and begin healing. A minor cut or scrape may bleed for a few seconds or minutes, but then it stops. Clean it up with soap and water, cover it with a bandage, and it begins to heal. Have you ever wondered why the bleeding stops? The answer is that blood has the ability to form a clot. Figure 37 9 summarizes the process. Blood clotting is made possible by plasma proteins and cell fragments called platelets. There are certain large in bone marrow that can break into thousands of small pieces. Each fragment of cytoplasm is enclosed in a piece of cell membrane and released into the bloodstream as a platelet. When platelets come into contact with the edges of a broken blood vessel, their surfaces become very sticky, and a cluster of platelets develops around the wound. These platelets then release proteins called clotting factors. The clotting factors start a series of chemical reactions that are quite complicated. In one reaction, a clotting factor called thromboplastin (thrahm-boh-plas-tin) converts prothrombin, which is found in blood plasma, into thrombin. Thrombin is an enzyme that helps convert the soluble plasma protein fibrinogen into a sticky mesh of fibrin filaments. These filaments stop the bleeding by producing a clot. Figure 37 10 shows the tangle of microscopic fibers in an actual blood clot. What are platelets? Break in Capillary Wall Clumping of Platelets Clot Forms Figure 37 9 Blood clotting is made possible by a number of plasma proteins and cell fragments called platelets. Calcium and vitamin K aid in converting prothrombin into thrombin. Demonstration Use a microprojector to display prepared slides of red blood, white blood, and platelets. Have students make a sketch of each structure. Then, call on students to describe the size, shape, and general appearance of each structure. Use Visuals Figure 37 9 Check students comprehension of the figure by having them identify each of the following in the drawings: red blood (red), platelets (pink), and fibrin filaments (blue). Then, ask: What is the main role of platelets in blood clotting? (The production of clotting factors such as thromboplastin) What role do calcium and vitamin K play in blood clotting? (They help convert prothrombin to thrombin.) Figure 37 10 Strands of fibrin trap blood, forming a net that prevents blood from leaving a damaged blood vessel. Using Analogies How is a blood clot similar to a screened-in porch? (magnification: 3000 ) FACTS AND FIGURES Red blood cell shapes Normal red blood are disk-shaped, but some people have red blood with abnormal shapes, such as spherical, oval, or sickle shapes. People with spherical red blood have an inherited disorder called spherocytosis. Because of their shape, the red become trapped and destroyed by the spleen, leading to anemia. Treatment may include removal of the spleen, which corrects the anemia but not the abnormal shape of the red. People with oval red blood have the inherited disorder elliptocytosis. This sometimes causes mild anemia but usually requires no treatment. People with sickle-shaped red blood have sickle cell disease, another inherited disorder and the most serious of the three disorders. Sickle cell disease can cause severe anemia, organ damage, deformities, and even death. Answers to... Platelets are cell fragments that form a cluster around a wound and release clotting factors. Figure 37 10 It is similar in forming a mesh barrier that prevents blood from leaving a damaged vessel (or that keeps insects out). Circulatory and Respiratory Systems 953

37 2 (continued) Tell students that the first successful blood transfusions were performed in the early 1800s by a British physician named James Blundell. At least half of Blundell s patients benefited from the transfusions, but many others had severe reactions to the transfused blood, and most of these died. In 1900, an Austrian physician, Karl Landsteiner, discovered the ABO blood group. Knowledge of ABO blood types explained Blundell s results and, in general, why some transfusions are successful and others are not. Answers 1. Type O is sometimes referred to as the universal donor. Type AB is sometimes referred to as the universal recipient. 2. Yes, because people with type A blood can safely receive type O blood, but people with type O blood cannot safely receive type A blood. 3. Student answers should reflect an understanding of blood groups and genetics. Suggested answer: People who have type O blood do not produce blood antigens and therefore can donate blood to any of the other blood groups safely. Because the alleles for type A and B are codominant, people with type AB blood can receive blood from all groups. The Lymphatic System Build Science Skills Applying Concepts Tell students that both malaria and sickle cell anemia are diseases that damage red blood. Ask: Why do people with malaria or sickle cell anemia often have enlarged spleens? (Damaged red blood are removed by the spleen. It becomes enlarged when there are many damaged.) Blood Transfusions Although the first successful transfusions of human blood were carried out in the 1820s, many recipients had severe reactions to the transfused blood, and several died. Today we know why. We inherit one of four blood types A, B, AB, or O which are determined by antigens on our blood. Antigens are substances that trigger an immune response. People with blood type A have A antigens on their, those with type B have B antigens, those with AB blood have both A and B, and those with type O have neither A nor B antigens. When blood types match, the transfusion is successful. However, transfusions are successful in some cases even when the blood types of the donor and the recipient do not match. Use the table to answer the questions that follow. FACTS AND FIGURES Lymphatic System Facts The thymus is the primary lymphoid organ and the site where lymphocytes acquire their antigen receptors. It attains its full size by age two, then decreases in size until puberty, after which it almost disappears. Secondary lymphoid organs include the spleen and tonsils. Most antibodies are made in the spleen. It consists of white pulp, where T are stimulated by antigen, and red pulp, where old red Blood Type of Donor 1. Drawing Conclusions Which blood type is sometimes referred to as the universal donor? Which is known as the universal recipient? 2. Drawing Conclusions In a transfusion involving the A and O blood types, does it make a difference which blood type belongs to the recipient and which to the donor? 3. Applying Concepts Write a brief explanation for the results in the chart using information about phenotypes and genotypes in blood group genes. (Hint: Review Section 14 1 if needed.) Blood Clotting Problems If the wound is small, within a few minutes the mesh of platelets and fibrin seals the wound, and bleeding stops. Most of the time, this clotting reaction works so well that we take it for granted. However, if one of the clotting factors is missing or defective, the clotting process does not work well. Hemophilia is a genetic disorder that results from a defective protein in the clotting pathway. People with hemophilia cannot produce blood clots that are firm enough to stop even minor bleeding. They must take great care to avoid injury. Fortunately, hemophilia can be treated by injecting extracts containing the missing clotting factor. The Lymphatic System A B AB O Blood Transfusions A B AB As blood circulates, some fluid leaks from the blood into the surrounding tissues. This isn t an altogether bad thing. A steady flow of fluid helps to maintain an efficient movement of nutrients and salts from the blood into the tissues. However, more than 3 liters of fluid leak from the circulatory system into surrounding tissues every day! If this leakage continued unchecked, the body would begin to swell with fluid not a very pleasant prospect. Fortunately, the interrelationship between two body systems does not allow this to happen. A network of vessels, nodes, and organs called the lymphatic system collects the fluid that is lost by the blood and returns it back to the circulatory system. The fluid is known as lymph (LIMF). Blood Type of Recipient = Unsuccessful transfusion = Successful transfusion blood are removed. The red pulp also manufactures new red blood when too many are lost during illness. Tonsils are small pieces of lymphatic tissue in the throat. Their primary role is to trap and destroy bacteria that enter the respiratory tract. One set of tonsils protrudes from each side of the pharynx behind the mouth. Another set, commonly called adenoids, is located higher up in the pharynx behind the nose. O 954 Chapter 37

Lymph collects in lymphatic capillaries and slowly flows into larger and larger lymph vessels. Like large veins, lymph vessels contain valves that prevent lymph from flowing backward. Ducts collect the lymph and return it to the circulatory system through two openings in the superior vena cava. The openings are under the left and right clavicle bones just below the shoulders. Figure 37 11 shows the lymphatic system. Along the length of the lymph vessels are small beanshaped enlargements called lymph nodes. Lymph nodes act as filters, trapping bacteria and other microorganisms that cause disease. When large numbers of microorganisms are trapped in the lymph nodes, the nodes become enlarged. If you have ever had swollen glands, you actually had swollen lymph nodes. Lymph vessels do not merely return excess fluid to the circulation. They also play a very important role in nutrient absorption. Lymph vessels lie near the that line the intestines, where they absorb fats and fat-soluble vitamins from the digestive tract and carry them to the blood. Lymph moves through the lymphatic system under osmotic pressure from the blood and is pushed along by the contractions of nearby skeletal muscles. It is important that there is a steady flow of lymph. Edema, a swelling of the tissues due to the accumulation of excess fluid, can occur when lymphatic vessels are blocked due to injury or disease. In addition to the lymph vessels and lymph nodes, the thymus and spleen also have important roles in the lymphatic system. The thymus is located beneath the sternum. Certain lymphocytes called T mature in the thymus before they can function in the immune system. T are the that recognize foreign invaders in the body. The spleen helps to cleanse the blood and removes damaged blood from the circulatory system. The spleen also harbors phagocytes that engulf and destroy bacteria and other microorganisms. 37 2 Section Assessment 1. Key Concept List the main function of red blood, white blood, and platelets. 2. Key Concept Describe the role of the lymphatic system. 3. What types of materials are dissolved in plasma? 4. Explain how blood clots. 5. Critical Thinking Inferring Sometimes lymph nodes must be surgically removed. Although more lymph vessels eventually grow, what result would you expect to see immediately after surgery? Superior vena cava Thymus Heart Thoracic duct Spleen Lymph nodes Lymph vessels Figure 37 11 The lymphatic system collects and returns fluid that leaks from blood vessels. The spleen is an organ whose main function is to destroy damaged red blood and platelets. Certain white blood called T lymphocytes, or T, mature in the thymus gland, which produces hormones that promote their development. Constructing a Concept Map Construct a concept map that shows the components of blood. Include information about the functions of the different components. (Be sure to include the different types of white blood.) Use Visuals Figure 37 11 Have students compare the distribution of lymphatic vessels with the distribution of blood vessels, shown in Figure 37 3. Then, ask: How are the lymphatic and circulatory systems related? (The lymphatic system collects fluid that seeps into the tissues from blood and returns it to the circulatory system.) Point out that the vein where this fluid is returned to the blood is called the superior vena cava. Have students find the superior vena cava in the figure. Also have them locate the clusters of lymph nodes. Ask: If you have a sore throat because of an infection, which lymph nodes might become swollen? (The lymph nodes in the neck) 3 ASSESS Evaluate Understanding Call on students at random to name each component of the blood. Call on other students to describe the function of each component. Reteach Using the chalkboard or a transparency, work with students to create a concept map of the functions of blood based on information in the opening paragraph of the section. Then, have students identify the parts of the blood involved in each function. Students concept maps should show that blood consists of plasma, platelets, red blood, and white blood, of which there are five main types: neutrophils, eosinophils, basophils, monocytes, and lymphoctyes. 37 2 Section Assessment 1. Red blood carry oxygen; white blood fight infection; platelets help blood to clot. 2. Its role is to collect fluid lost by blood and return it to the circulatory system. 3. Gases, salts, nutrients, enzymes, hormones, waste products, and plasma proteins 4. When platelets come in contact with the broken edges of a blood vessel, their surfaces become sticky. A cluster of platelets develops around the wound. The platelets release clotting factors, which start reactions that produce a blood clot. 5. Areas without lymph nodes and vessels would retain excess fluid and become swollen immediately after surgery. If your class subscribes to the itext, use it to review the Key Concepts in. Circulatory and Respiratory Systems 955