Anatomy & Physiology

Anatomy & Physiology Study Guide

21.10 Immune Disorders Due to the complexity of the immune system response, their is a lot of room for error. A variety of clinical conditions result from disorders of the immune function. Autoimmune disorders develop when the immune response inappropriately targets normal body cells and tissues. In an immunodeficiency disease , either the immune system fails to develop normally, or the immune response is blocked in some way. For example, allergies are a common immune disorder which luckily is far less dangerous. 21.11 Aging The immune response diminishes with advancing age. As you will see, with advancing age, the immune system becomes less effective at combating diseases. T cells become less responsive to antigens; hence, fewer cytotoxic T cells respond to an infection. This effect may, at least in part, be associated with the gradual involution of the thymus and a reduction in circulating levels of thymic hormones. Due to the reduction in the number of helper T cells, B cells are less responsive; hence, antibody levels do not rise as quickly after antigen exposure. The net result is an increased susceptibility to viral and bacterial infections. 21.12 Chapter Twenty-One Review Anatomical barriers and defense mechanisms constitute a nonspecific defense, and lymphocytes provide specific defenses: • The entire lymphatic system (cells, tissues, and organs) plays a central role in defending the body against various pathogens or other disease-causing organisms. • The primary cells of the lymphatic system, lymphocytes, are crucial to the immune response against specific threats to the body. The ability to resist infection and disease through the activation of specific defenses is known as immunity. Lymphatic vessels, lymphocytes, lymphoid tissues, and lymphoid organs function in body defenses: • A network of lymphatic vessels (i.e., lymphatics) make up the lymphatic system that carries lymph (a plasma-like fluid with lower concentrations of proteins) An array of lymphoid tissues and lymphoid organs is connected to the lymphatic vessels. • The lymphatic system produces, maintains, and distributes lymphocytes (which attack invading organisms, abnormal cells, and foreign proteins); it also helps maintain blood volume and eliminate local variations in the composition of interstitial fluid.

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