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Introduction
Innate immune cells serve as the first line of defense against infections. Antigen-presenting cells notify lymphoid cells of an infection, coordinating the adaptive response, producing memory cells, and avoiding recurrent infections. The immune system’s specialised architecture and microanatomy, known as lymphoid organs, are distributed throughout the body and provide the coordination required for a thorough immunological response.
What are Lymphoid Organs?
The lymphatic system, or lymphoid system, is an organ system in vertebrates that is part of the immune system, and complementary to the circulatory system. It comprises of a large network of lymphatic vessels, lymph nodes, lymphatic or lymphoid organs, and lymphoid tissues.
What are Primary Lymphoid Organs?
Primary Lymphoid Organs create and develop lymphocytes. They provide an environment for stem cells to multiply and grow into B and T cells:
The primary peripheral lymphoid organs examples are the red bone marrow and the thymus gland. The blood section briefly described the formation of white blood cells haemolysis. T-cells and B-cells are both produced in the bone marrow. T lymphocytes, unlike B cells, which develop in the bone marrow, must go to the thymus to mature.
What are Secondary Lymphoid Organs?
Secondary lymphoid tissues, organised as a series of filters, monitor extracellular fluids such as lymph, tissue fluid, and blood. Each of these fluids is filtered by lymphoid tissue with a unique structure. Secondary lymphoid tissues also activate lymphocytes. Lymph nodes, tonsils, spleen, Peyer’s patches, and mucosa-related lymphoid tissue.
Filtering Tissue Fluid
Non-encapsulated or partially encapsulated lymphoid tissue aggregations are also known as Mucosa Associated Lymphoid Tissue MALT filters fluid from the body. This makes up around 85 per cent of the lymphoid tissue in the non-sterile mucosa. They are normally microscopic, measuring around 1mm in diameter, except for the tonsils, peyer’s patches, and appendix.
These lymphoid aggregations are generally found near moist epithelial surfaces, such as the mucous membranes of the digestive, respiratory, and reproductive systems. These tissues’ epithelia have mechanisms to keep bacteria and other external items out of the body, but they are not foolproof. As a result, any bacteria or microbes that make it past the epithelia can elicit a response from the lymphoid cells in these areas. Activated B-cells can transform into plasma cells and produce antibodies in situ in certain environments. Larger permanent organ lymphocytes such as tonsils may patrol the surrounding tissue and respond quickly to antigens.
What are the Three Primary Roles of the Lymphoid Organs?
The Lymphoid Organs serves three functions:
- The removal of excess fluid from body tissues.
- Absorption of fatty acids and subsequent chyle transport to the circulatory system
- Immune cells such as lymphocytes, monocytes, and antibody-producing cells called plasma cells) are produced.
Type of Lymphoid Organs
Lymph nodes-These are little bean-shaped structures that produce and store anti-infective cells. They are part of the Lymphoid Organs. Lymph nodes contain lymph. They become swollen and inflamed when the body fights an infection.
Bone marrow – The inside of some bones, such as the hip and thigh bones, contains yellow tissue that produces white blood cells. The stem cells are present in the spongy tissue that lines the insides of these bones. It is the primary lymphoid organ producing blood cells, including lymphocytes. In the bone marrow, immature lymphocytes develop into antigen-sensitive lymphocytes.
Spleen– It is the largest Lymphoid Organ in the body. It is endowed with anti-infective white blood cells. The spleen is an organ that aids the body in eliminating old, damaged blood cells.
Lymphoid Tissue –Mucosa-associated lymphoid tissue is lymphoid tissue that is located in the lining of key passageways such as the respiratory, digestive, and urogenital tracts.
What Happens in Lymphoid Organs for Immunity?
What happens in lymphoid organs with respect to immunity includes two primary things – the red bone marrow, which generates blood and immune cells, and the thymus, which grows T-lymphocytes. The lymph nodes and spleen are the principal secondary lymphoid organs that filter pathogens and maintain a mature lymphocyte population. When naïve lymphocytes come into contact with antigen in secondary lymphoid tissues, they initiate a basic immunological response that produces both effector and memory cells.
