Immune System Structure and Function

Immune System Structure and Function

• The lymphoreticular system is a complex network of cells, found throughout the body, responsible for immunity
• It includes lymphoid and reticuloendothelial components
• Lymphoid cells, like lymphocytes and plasma cells, confer specific immunity
• Reticuloendothelial cells, including phagocytic cells and antigen-presenting cells, provide nonspecific immunity
• These cells eliminate pathogens and foreign agents from blood and tissues

Specific and Cell-mediated Immunity

• Specific immune response to antigens has two types:
  • Humoral immunity: mediated by antibodies produced by plasma cells
  • Cell-mediated immunity: mediated by sensitized lymphocytes
• The immune system is organized into various tissues/organs
• Lymphoid tissues include tonsils, Peyer's patches, and appendix
• Lymphoid tissues/organs are categorized into central (primary) and peripheral (secondary)

Central (Primary) Lymphoid Organs

• Central/primary organs are critical sites for lymphopoiesis.
• These organs allow for the development of precursor lymphocytes into immunocompetent cells.
• Examples are thymus and bone marrow
• Thymus is vital for T lymphocyte maturation.
• Bone marrow is where B lymphocytes develop

Thymus Structure and Function - Detail

• The thymus is the first lymphoid organ to develop.
• It reaches its maximum size at puberty and then shrinks.
• The thymus is made of two lobes located above the heart.
• The thymus has distinct cortex and medulla regions
• The thymus is responsible for T cell development and maturation, enabling them to recognize antigens.

Peripheral (Secondary) Lymphoid Organs

• Peripheral lymphoid organs (lymph nodes, spleen, MALT) are sites for mature lymphocytes to interact with antigens.
• Lymph nodes are numerous throughout the body.
• Lymph nodes play a role in the initial immune response.
• Lymph nodes filter lymph, a fluid containing lymphocytes and other components.
• Lymph nodes have a cortex and medulla.
• Spleen is the largest lymphoid organ
• The spleen filters blood and plays a key role in mounting immune responses to blood-borne pathogens and antigens.
• Spleen has white and red pulp to eliminate pathogens and old cells.
• Mucosa-associated lymphoid tissues (MALT) are collections of lymphoid tissue located in mucosal membranes. Includes tonsils, Peyer's patches.
• MALT plays an important role in defense, especially in the prevention of pathogens entering the body through mucosal surfaces.

Lymphatic Circulatory System

• Leukocytes utilize the lymphatic and cardiovascular systems.
• The lymphatic system is a network for fluid circulation, collecting and returning lymphatic fluid to the circulatory system.
• Lymph nodes are key components of the lymphatic system, processing lymph and filtering out foreign particles.
• The spleen filters blood, plays role in immune response to blood-borne pathogens.

This quiz explores the intricate structure and functionality of the immune system, highlighting components like the lymphoreticular system. It covers topics such as specific and cell-mediated immunity, as well as the various central and peripheral lymphoid organs involved in immune responses.