The Lymphatic and Immune System Chapter 21 Quiz

Lymphatic and Immune Systems

• The immune system consists of cells and organs that destroy pathogens, while the lymphatic system consists of vessels, cells, and organs that bring excess fluid to the bloodstream and filter pathogens from the blood.
• Lymph is the interstitial fluid in the lymphatic system, and it is responsible for absorbing dietary lipids and fat-soluble vitamins, which are then transported to the liver through lymphatic vessels.

Anatomy of the Lymphatic System

• The lymphatic system has open-ended capillaries that feed into larger vessels, eventually leading to the subclavian vein.
• Capillaries are composed of simple squamous endothelial cells.
• There are approximately 500-600 lymph nodes located along the lymphatic vessels.
• Lymph movement is not pumped but rather relies on breathing, muscle contraction, and body movements.
• One-way valves ensure that lymph moves towards the heart.
• Areas without lymph vessels include bone marrow, CNS, teeth, and cornea.

Organization of Immune Function

• The immune system has three layers of defense: barrier defenses, innate immune response, and adaptive immune response.
• Barrier defenses prevent invasion, including skin and mucous membranes.
• Innate immune response is rapid but non-specific, consisting of cells such as phagocytic cells and natural killer cells.
• Adaptive immune response is slower but highly specific, involving lymphocytes that coordinate immune responses.

Lymphocytes

• B cells produce plasma cells that bind to specific antigens, leading to antibody production.
• T cells can secrete chemokines to bring other immune cells to the area or destroy cells infected with intracellular pathogens.
• Plasma cells secrete soluble antibodies that bind to specific antigens.
• Natural killer cells have cell-killing granules and are part of the innate immune response.

Lymphoid Organs and Development

• Bone marrow is responsible for B cell development, while the thymus is responsible for T cell maturation.
• Secondary lymphoid organs, including lymph nodes, spleen, and lymphoid nodules, are important for immune response.
• Bronchus-associated lymphoid tissue (BALT) is a type of lymphoid follicle located on the bronchii that is effective against inhaled pathogens.

Barrier Defenses and the Innate Immune Response

• Barrier defenses include skin, sweat, mouth, stomach, mucosal surfaces, and normal flora.
• Innate immune response is rapid but non-specific, involving cells such as macrophages, neutrophils, and natural killer cells.

Innate Immune Cells

• Macrophages are phagocytic cells that cooperate with lymphocytes.
• Neutrophils are phagocytic cells that are attracted to sites of infection through chemotaxis.
• Monocytes differentiate into macrophages or dendritic cells.
• Natural killer cells induce apoptosis in infected cells by releasing perforins and granzymes.

Adaptive Immune Response

• The adaptive immune response is highly specific and involves lymphocytes that coordinate immune responses.
• T cells recognize and attack a wide variety of pathogens, with 100 trillion different receptors.
• Primary adaptive response involves the initial infection, while secondary adaptive response involves immunological memory.

T Cell-Mediated Immune Responses

• T cells recognize antigens on the surface of antigen-presenting cells.
• Antigen presentation involves the cleavage of antigens into small pieces, which are then presented on the membrane attached to a major histocompatibility complex (MHC) molecule.

T Cells

• T cells recognize antigens on the surface of antigen-presenting cells, which can be either professional or non-professional antigen-presenting cells.
• Many human cells can express class I MHC molecules, while only professional antigen-presenting cells can express class II MHC molecules.

Secondary Lymphoid Organs

• Lymph nodes filter lymph and remove debris and pathogens, with dendritic cells and macrophages killing many pathogens.
• Spleen is known as the "filter of the blood" and holds many dendrites and macrophages.
• Lymphoid nodules are dense clusters of lymphocytes found in respiratory and digestive tracts (tonsils).

Development and Differentiation

• T cell tolerance involves the elimination of T cells that might attack one's own body.
• Only 2% of T cells successfully mature from a thymocyte, involving two steps: positive selection and negative selection.
• Positive selection involves the presentation of an MHC molecule, while negative selection involves the presentation of a self-antigen.

Mechanism of T Cell Response

• Clonal expansion involves the rapid division of mature T cells in response to antigen recognition, leading to a strong response against a pathogen.
• Clonal selection involves the process of antigen binding only to the T cell with that specific receptor.

T Cell Types

• Helper T cells secrete cytokines to enhance other immune responses and can be divided into two types: Th1 cells and Th2 cells.
• Th1 cells regulate activity of macrophages and other T cells, while Th2 cells regulate activity of B cell differentiation into plasma cells that make antibody.
• Cytotoxic T cells kill target cells by inducing apoptosis, similar to natural killer cells.
• Regulatory T cells suppress other T cell immune responses.