Bacteria are removed from lymph and blood in the:

Question

Quizplus · Accepted Answer

11ecba2d_1024_1f06_a3bf_331f6ff44eb4_MD0008_00 The lymphatic system is a network of vessels that collect and transport lymph, ultimately draining this fluid into the bloodstream. The lymphatic system is particularly important to the immune response and includes the following lymphoid tissues and organs, which facilitate immune cell proliferation and function: The bone marrow, a spongy tissue lining the inside of bones, is responsible for the production of red blood cells and white blood cells (eg, lymphocytes) from hematopoietic stem cells. The thymus receives immature T lymphocytes migrating from the bone marrow and facilitates their maturation. During this process, any T lymphocytes that recognize self-antigens die, preventing the release of lymphocytes able to mount attacks against the body's own tissues. However, T lymphocytes that do not bind self-antigens mature and enter the blood and lymph, where they bind foreign antigens and mount immune responses. Lymph nodes, organs clustered along lymph vessels, filter lymph as it flows through the lymphatic system. Macrophages housed within lymph nodes identify a variety of pathogens in lymph and destroy them via phagocytosis. In addition, B lymphocytes and T lymphocytes bind specific foreign antigens in lymph, inducing immune responses against invading pathogens. The spleen has extensive capillary networks through which blood is filtered. White blood cells housed within the spleen recognize and bind foreign antigens in the blood, mounting immune responses against these circulating pathogens. In addition, spleen macrophages remove and destroy old and damaged red blood cells. Platelets and other white blood cells are also stored in the spleen and released into the blood as needed. Because lymph nodes filter lymph and the spleen filters blood, bacteria circulating through lymph are removed in the lymph nodes and bacteria circulating through blood are removed in the spleen. (Choices A and C) Although white blood cells are produced in bone marrow, bone marrow cells do not remove bacteria from blood or lymph. (Choice D) Immune cells circulate throughout the body via lymph vessels; however, pathogens are mainly removed from lymph at lymph nodes (not lymph vessels). The thymus is the site of T-cell maturation, but it does not filter blood or lymph. Educational objective: In the lymph nodes, white blood cells remove and mount immune responses against pathogens from the lymph, whereas in the spleen, white blood cells remove pathogens and damaged or old red blood cells from the blood.

Bacteria Are Removed from Lymph and Blood in The