Page 107 - Alaska A & P Primer

Production of erythrocytes in the marrow occurs at the staggering rate of more than 2 mil- lion cells per second. For this production to occur, a number of raw materials must be pre- sent in adequate amounts. These include the same nutrients that are essential to the pro- duction and maintenance of any cell, such as glucose, lipids, and amino acids.
Erythrocytes are produced in the bone marrow and sent into the circulation. At the end of their lifecycle, they are destroyed by macrophages, and their components are recycled.
18.4 Leukocytes and Platelets
The leukocyte, commonly known as a white blood cell (or WBC), is a major component of the body’s defenses against disease. Leukocytes protect the body against invading microor- ganisms and body cells with mutated DNA, and they clean up debris. Platelets are essential for the repair of blood vessels when damage to them has occurred; they also provide growth factors for healing and repair. Although leukocytes and erythrocytes both origi- nate from hematopoietic stem cells in the bone marrow, they are very different from each other in many significant ways.
The three major groups of lymphocytes include natural killer cells, B cells, and T cells. Natural killer (NK) cells are capable of recognizing cells that do not express “self” proteins on their plasma membrane or that contain foreign or abnormal markers. These “nonself” cells include cancer cells, cells infected with a virus, and other cells with atypical surface proteins. Thus, they provide generalized, nonspecific immunity. The larger lymphocytes are typically NK cells.
Most leukocytes have a relatively short lifespan, typically measured in hours or days. Pro- duction of all leukocytes begin in the bone marrow under the influence of CSFs and inter- leukins. Secondary production and maturation of lymphocytes occurs in specific regions of lymphatic tissue known as germinal centers. Lymphocytes are fully capable of mitosis and may produce clones of cells with identical properties. This capacity enables an individual to maintain immunity throughout life to many threats that have been encountered in the past.
18.5 Hemostasis
Hemostasis is the physiological process by which bleeding ceases. Hemostasis involves three basic steps: vascular spasm, the formation of a platelet plug, and coagulation, in which clotting factors promote the formation of a fibrin clot. Fibrinolysis is the process in which a clot is degraded in a healing vessel. Anticoagulants are substances that oppose
18.4 OBJECTIVES
1. Describe the general characteristics of leukocytes
18.5 OBJECTIVES
1. Describe the three mechanisms involved in hemostasis
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State of Alaska EMS Education Primer - 2016
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