Chapter 17 Notes

Chapter 17 Blood I. Overview: Composition of Blood (p. 513, Fig. 17.1) A. Blood is the fluid in the vessels of the cardiovascular system; the cardiovascular system is a subdivision of the circulatory system (the blood, the heart, and the blood vessels). B. Blood is a specialized type of connective tissue; it consists of formed elements (blood cells) suspended in plasma. C. Hematocrit (or packed cell volume) is a measure of the ratio of red cells to plasma. Average hematocrit is 45%, but varies among individuals and between males and females.

II. Blood Plasma (pp. 513–514) A. Plasma contains 90% water; other components are nutrients, respiratory gases, salts, hormones, and plasma proteins.

III. Formed Elements (pp. 514–519, Figs. 17.2–17.6, Table 17.1) A. Erythrocytes, or red blood cells (RBCs), are the most numerous of the formed elements; red blood cells are biconcave discs that lack nuclei, and are packed with the oxygen-carrying protein, hemoglobin. (pp. 514–515, Figs. 17.2–17.3) B. Leukocytes, or white blood cells (WBCs), are far less numerous than RBCs; white blood cells are crucial to the body’s defense against diseases caused by bacteria, viruses, and parasites in the body’s loose connective tissues. (pp. 515–518, Figs. 17.2 and 17.4–17.5) 1. There are five types of leukocytes, divided into two groups (granulocytes and agranulocytes) based on the presence or absence of distinct membrane-bound organelles; the five types in order of relative percentages are neutrophils, lymphocytes, monocytes, eosinophils, and basophils. C. Platelets, or thrombocytes, are not cells in the strict sense but fragments of large, multinucleated cells called megakaryocytes; platelets function as clotting agents. (p. 519, Figs. 17.2 and 17.6)

IV. Blood Cell Formation (pp. 519–523, Figs. 17.7–17.8) A. The process of blood cell formation begins in the embryo and continues throughout life; the process is called hematopoiesis or hemopoiesis. (pp. 519–520) B. Bone marrow, collectively the body’s second largest organ, is the site of hematopoiesis; there are two types of bone marrow, red and yellow. (pp. 520–521, Fig. 17.7) 1. Red bone marrow actively generates red blood cells. 2. Yellow bone marrow is basically dormant and its color reflects the high content of fat cells. C. All blood cells continuously arise from blood stem cells; two types of progenitor cells arise directly from blood stem cells: lymphoid stem cells, which give rise to lymphocytes, and myeloid stem cells, which give rise to all other blood cells. (pp. 521–523, Fig. 17.8)

D. The genesis of erythrocytes begins with proerythroblasts and continues through various stages during which hemoglobin accumulates and the nucleus and organelles are extruded. (p. 521) E. Granular leukocytes begin as myeloblasts; monocytes and lymphocytes resemble stem cells with minimal structural changes. (pp. 521–522)

V. Blood Disorders (p. 523, Fig. 17.9) A. Examples of blood disorders are polycythemia, anemia, sickle cell disease, leukemia, and thrombocytopenia.

VI. The Blood Throughout Life (p. 525) A. In the embryo, blood stem cells develop in blood islands of the yolk sac during week 3; embryonic hematopoietic organs are the liver, spleen, and bone marrow. B. The most common blood disorders that appear with aging are chronic leukemias, anemias, and clotting disorders. (p. 525)

Chapter 17: Blood To the Student Blood is the fluid of the circulatory system and plays many vital interactive roles within the body. Blood interacts with the respiratory system in the delivery of oxygen to cells and removal of waste from tissues of the body. Nutritive interactions result in the transport of food molecules from the small intestine to the liver and, ultimately, to the cells of the body. Blood carries metabolic wastes and excess water to the kidneys, resulting in urine production and excretory interaction. Regulatory interaction involves the transport of hormones from the site of production to target tissues. Other functions involve the regulation of body heat and protection against foreign invaders, such as microbes and toxins. Blood keeps you in contact with your external environment. Blood is essential for survival, and any region of the body deprived of blood dies in minutes. Obviously, it is important for you to understand the nature of blood because with every succeeding topic you study in anatomy, blood is featured and is a focal point in some way.

Step 1: Distinguish the circulatory system from the cardiovascular system. - Define circulatory system, including functions of blood. - Define cardiovascular system. - Define lymphatic system.

Step 2: Describe the composition of blood, including functions of its components. - Define and describe plasma. - Distinguish between plasma and serum. - Define hematocrit. - List the formed elements of blood. - Describe the structure, function, and life span of erythrocytes. - Summarize the role of hemoglobin in the blood. - Discuss the function of leukocytes. - Distinguish between granulocytes and agranulocytes, listing examples of each. - Describe similarities and differences between lymphocytes and monocytes.

- Distinguish between antigen and antibody. - Distinguish between T cells and B cells, describing how they attack cells. - Define apoptosis. - Define macrophage and describe phagocytosis. - Define platelet and describe its functions. - Distinguish between thrombus and embolus.

Step 3: Explain blood cell formation. - Define hematopoiesis and describe bone marrow as a site of blood cell formation. - Distinguish between yellow bone marrow and red bone marrow both structurally and functionally. - Define blood stem cell. - Describe the formation of red blood cells. - Describe the formation of white blood cells and platelets.

Step 4: Describe common blood disorders and blood embryologic development. - Name and describe symptoms of blood disorders, such as anemia, polycythemia, sickle-cell disease, and leukemia. - Name four hematopoietic organs in the fetus.