If you answered fewer than four items correctly dont stop circu lating Never

If you answered fewer than four items correctly dont

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If you answered fewer than four items correctly, don’t stop circu- lating. Never give up. Need inspiration? Think of the stem cell precursor that eventually emerges to become a mighty RBC. 338 HEMATOLOGIC SYSTEM ✰✰✰ ✰✰ Let’s circulate to chapter 10.
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Understanding the immune system The body protects itself from infectious organisms and other harmful invaders through an elaborate network of safeguards called the host defense system. This system has three lines of defense: physical and chemical barriers to infection the inflammatory response the immune response. Physical barriers, such as the skin and mu- cous membranes, prevent most organisms from invading the body. Organisms that penetrate this first bar- rier simultaneously trigger the inflammatory and immune respons- es. Both responses involve stem cells in the bone marrow that form blood cells. Structures of the immune system These five structures in the body make up the immune system: bone marrow lymph nodes • thymus 10 Immune system In this chapter, you’ll learn: the five structures of the immune system cell-mediated immunity, humoral immunity, and the complement system, and how they work the pathophysiology, signs and symptoms, diagnostic tests, and treatments for common immune system disorders. Just the facts Immune system We cells have a lot to do with the immune system.
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• spleen • tonsils. Bone marrow B-cells are produced and develop in the bone marrow then mi- grate to the lymph nodes. Lymph nodes Lymph nodes are distributed along lymphatic vessels throughout the body. They filter lymphatic fluid, which drains from body tis- sues and later returns to the blood as plasma. Double agents? The lymph nodes also remove bacteria and toxins from the circu- latory system. This means that, on occasion, infectious agents can be spread by the lymphatic system. Thymus The thymus, located in the mediastinal area (between the lungs), secretes a group of hormones that enable lymphocytes to develop into mature T cells. “T” stands for “tough” T cells attack foreign or abnormal cells and regulate cell-mediated immunity. Spleen The largest lymphatic organ, the spleen functions as a reservoir for blood. Cells in the splenic tissue, called macrophages, clear cellular debris and process hemoglobin. Tonsils The tonsils consist of lymphoid tissue and also produce lympho- cytes. Guarding against air raids The location of the tonsils allows them to guard the body against airborne and ingested pathogens. Types of immunity Certain cells have the ability to distinguish between foreign matter and what belongs to the body—a skill known as immunocompe- tence. When foreign substances invade the body, two types of 340 IMMUNE SYSTEM Basically, my job is to destroy target cells through the release of lymphokines.
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immune responses are possible: cell-mediated immunity and humoral immunity.
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