The Immune System - Lymphoid Organs

Humans often get sick especially cold, flu and are more prone to different types of infections caused by pathogens.  There are several ways for the micro-organisms to enter the human body and create havoc. Humans are always exposed to micro-organisms, from the dust and dirt on the road or while working, playing and traveling. All these activities facilitate the entry of pathogens into our body.

Overall, our immune system performs a remarkable job by defending against disease-causing microorganisms. But in certain circumstances, it fails to protect us and thus the pathogens invade successfully and make us sick.

Is it possible to intervene in this process and boost our immune system? Let us explore the immune system and its organ -Lymphoid organs.

The Immune System

The Immune System

The immune system is our body’s best defensive system. It functions against infringing microorganisms and keeps us healthy. Immunology is a branch of biology which deals with complex body functions of the immune system. The ability to tackle antigens or pathogens and being healthy is referred to as immunity.

The immune system is composed of cells, tissues, and organs that work unitedly in protecting our body. This system defends the human body from the trespassing pathogens in a variety of ways.  They work based on memory, some are innate, and some are acquired. Hence, they function in allergies, autoimmunity and organ transplantation.

The most important cells involved in the immune system is white blood cells (or) leukocytes, which are involved in destroying disease-causing organisms or substances. Apart from the leukocytes, lymphoid organs, tissues, and proteinaceous molecules antibodies are also involved in the defensive system.

Lymphoid Organs

Organs immune system

The organs of the immune system which are involved in defending the body against invading pathogens causing infections or spread of tumors is termed as Lymphoid organs. It includes bone marrow, blood vessels, lymph nodes, lymphatic vessels, thymus, spleen, and various other clusters of lymphoid tissue.

Lymphoid organs are the site of origin, maturation, and proliferation of lymphocytes. They exist as primary, secondary or tertiary and these are based on their stage of development and maturation. These organs consist of fluid connective tissues with different types of leukocytes or white blood cells. The highest percentage of Lymphocytes are present in the white blood cells or leukocytes.

Primary lymphoid organs

The primary lymphoid organs produce and allow the maturation of lymphocytes. It also serves by generating lymphocytes from immature progenitor cells. Therefore it is referred as the central lymphoid organs.

Examples of primary lymphoid organs include thymus and the bone marrow.3

Secondary lymphoid organs

The secondary lymphoid organs are referred to as the peripheral lymphoid organs as they are involved in promoting the sites for the interaction of lymphocytes with the antigen to become effector cells. They initiate an adaptive immune response. The secondary lymphoid organs

Examples of secondary lymphoid organs spleen, tonsils, lymph nodes, appendix, etc. are secondary lymphoid organs.

Tertiary lymphoid organs

The tertiary lymphoid organs usually contain very less number of lymphocytes. It plays an important role during the inflammation process.

Stay tuned with BYJU’S to learn more about the immune system and its organs.


Practise This Question

The thoracic and right lymphatic ducts return lymph to the ______.