What is the Difference Between Central and Peripheral Lymphoid Organs

The key difference between central and peripheral lymphoid organs is that central lymphoid organs act as the sites for the formation and maturation of lymphocytes, while peripheral lymphoid organs maintain mature naïve lymphocytes and initiate adaptive immune responses.

The lymphatic system consists of an organ system that plays a major role in the immune system and complimentary circulatory system of vertebrates. It comprises a network of lymphatic vessels, lymph organs, and lymphoid tissues. These vessels carry a clear fluid called lymph towards the heart for circulation. Lymph mostly carries lymphocytes. Lymphoid organs play a major role in the production and activation of lymphocytes. Such organs include lymph nodes, spleen, tonsils, thymus, and bone marrow. Major functions of the lymphatic system include providing a return route to the blood for a surplus of three liters and immune defense.

CONTENTS

1. Overview and Key Difference
2. What are Central Lymphoid Organs
3. What are Peripheral Lymphoid Organs
4. Similarities – Central and Peripheral Lymphoid Organs
5. Central vs Peripheral Lymphoid Organs in Tabular Form
6. Summary – Central vs Peripheral Lymphoid Organs

What are Central Lymphoid Organs?

Central lymphoid organs generate lymphocytes from immature progenitor cells. They are also known as primary lymphoid organs and constitute the bone marrow and thymus. These organs are involved in the production and clonal selection of lymphocyte tissues.

Figure 01: Lymphoid Organs and Lymphatic System

Bone marrow influences the creation of T cell precursors and the production and maturation of b cells. These are essential cells in the immune system. B cells enter the circulatory system and travel to the peripheral lymphoid organs in search of pathogens. T cells travel from the bone marrow to the thymus, where they mature further. Mature T cells join B cells to destroy pathogens. The remaining T cells go through apoptosis and programmed cell death. Thymus increases in size from birth. This is due to post-natal antigen stimulation. It is active during neonatal and pre-adolescent periods. The thymus usually consists of lobules divided by a septum. The loss or lack of the thymus results in severe immunodeficiency. T cells mature from thymocytes. The proliferation and selection process occurs in the thymic cortex before entering the medulla.

What are Peripheral Lymphoid Organs?

Peripheral lymphoid organs maintain mature naïve lymphocytes and initiate adaptive immune responses. They are also known as secondary lymphoid organs and include lymph nodes and the spleen. The spleen synthesizes antibodies and removes bacteria and blood cells that are antibody-coated through blood and lymph node circulation. This organ is the center of the activity of the mononuclear phagocyte system. Monocytes in the spleen move to injured tissues, turn into dendritic cells and macrophages to promote tissue healing. The absence of the spleen causes pre-deposition to some infections.

The lymph node contains a collection of lymphoid tissues. They are located in the lymphatic system at specific intervals. Usually, afferent lymph vessels bring in lymph and are drained out through the efferent lymph vessel. Lymph nodes are present as clusters in proximal ends of limbs such as armpits, groin, neck region, chest, and abdominal areas such as vessels of intestines, inguinal region, and pelvis. Lymph nodes consist of lymphoid follicles in the cortex. They are a dense collection of lymphocytes. Most immature T cells are located in the cortex. The region called the paracortex surrounds the medulla, and it consists of immature and mature T cells. Lymphocytes usually enter lymph nodes through high endothelial venules in the paracortex. Lymph nodes help in the selection of B cells, and this takes place in the germinal center of lymph nodes.

What are the Similarities Between Central and Peripheral Lymphoid Organs?

• Central and peripheral lymphoid organs belong to the lymphatic system.
• They play a major role in the immune system.
• Both types of organs help in the maturation of lymphocytes.
• Moreover, both play an important role in the functioning of the immune system.

What is the Difference Between Central and Peripheral Lymphoid Organs?

Central lymphoid organs act as the sites for the formation and maturation of lymphocytes, while peripheral lymphoid organs maintain mature naïve lymphocytes and initiate adaptive immune responses. Thus, this is the key difference between central and peripheral lymphoid organs. Also, central lymphoid organs are called primary lymphoid organs, whereas peripheral lymphoid organs are called secondary lymphoid organs. Moreover, bone marrow and thymus are central lymphoid organs, while lymph nodes and spleen are examples of peripheral lymphoid organs.

The following table summarizes the difference between central and peripheral lymphoid organs.

Summary – Central vs Peripheral Lymphoid Organs

The lymphatic system consists of an organ system that plays a major role in the immune system. Central and peripheral lymphoid organs play a major role in this system. The key difference between central and peripheral lymphoid organs is that central lymphoid organs act as the sites for the formation and maturation of lymphocytes, whereas peripheral lymphoid organs maintain mature naïve lymphocytes and initiate adaptive immune responses. Moreover, central lymphoid organs are the sites where blood and immune cells production and T-lymphocyte maturation take place. These organs include bone marrow and thymus. Peripheral lymphoid organs are the site where differentiation and antigen dependent proliferation of lymphocytes takes place. These organs include lymph nodes and spleen. So, this is another difference between central and peripheral lymphoid organs.

Reference:

1. “Central Lymphoid Organs.” Biology Discussion.
2. “Lymphoid Organ.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “2201 Anatomy of the Lymphatic System” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia

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