What is the Difference Between Lymph Node and Spleen

The main difference between lymph node and spleen is that a lymph node is the small mass of tissues located along the lymphatic vessels whereas spleen is an organ found in vertebrates, which is structurally similar to a large lymph node. Furthermore, lymph nodes filter pathogens in the lymph while the spleen filters the pathogens in the blood.

Lymph nodes and spleen are secondary lymphoid organs found in the vertebrate immune system. Their main function is to filter body fluids to capture pathogens, making them in contact with immature lymphocytes.

Key Areas Covered

1. What is a Lymph Node
     – Definition, Structure, Function
2. What is Spleen
     – Definition, Structure, Function
3. What are the Similarities Between Lymph Node and Spleen
     – Outline of Common Features
4. What is the Difference Between Lymph Node and Spleen
     – Comparison of Key Differences

Key Terms

Blood, Lymph, Lymph Node, Lymphocytes, Secondary Lymphoid Organs, Spleen

What is a Lymph Node

The lymph node is a type of secondary lymphoid organ of the lymphatic system. A number of lymph nodes occur along the lymphatic vessels. Generally, a lymph node is a kidney-shaped organ whose size can range from millimeters to 1-2 centimeters. Lymph nodes are more concentrated within the trunk of the body. The main function of a lymph node is to filter lymph to capture pathogenic antigens. Since it is a secondary lymphoid organ, a lymph node hosts lymphocytes allowing them to capture antigens, developing an adaptive immune system.

Figure 1: Lymph Node – Anatomy

The anatomical structure of a lymph node mainly consists of two main regions: outer cortex and inner medulla. The cortex consists of a capsule, which surrounds the medulla, except in the regions of hilum. The branches of the capsule enter into the subcapsular sinus. From the superficial region, afferent lymphatic channels perforate the capsule.

Furthermore, the cortex consists of lymphoid follicles, containing follicular B cells cluster in the superficial cortex. These follicles produce germinal centers, especially when they are in contact with pathogenic antigens. In contrast, the T lymphocytes cluster in the paracortex. Lymph nodules refer to the compartments found inside the lymph node, consisting of cortical regions with B and T cells and the medullary regions in the base. In addition, the medullary region consists of cords and sinus. Medullary sinus is in contact with the efferent lymphatic vessels.

Figure 2: Flow inside the Lymph Node

Moreover, thin reticular fibers belong to the reticular connective tissue along with elastin that forms a supportive network called a reticulin inside the lymph node. It provides structural support and sites for adhesion for lymphocytes and other cells in the immune system including macrophages and dendritic cells.

What is the Spleen

The spleen is the largest organ of the lymphatic system located in the upper left portion of the abdominal cavity, beneath the diaphragm and behind the stomach. Moreover, it resembles a large lymph node, divided into lobules. On the contrary, the main functional difference between lymph node and spleen is the presence of blood in the sinus instead of the lymph. In the fetus, spleen involves the active formation of blood. In adults, it mainly serves as a filtration organ, filtering all the foreign elements from the blood. Also, spleen removes old or defective red blood cells, recycling hemoglobin. In addition, it serves as a blood reservoir, storing blood, especially during exercises. The main splenic disease type is the enlarged spleen, a situation clinically known as splenomegaly.

Figure 3: Spleen

Anatomy wise, the length of the spleen can vary from 7-14 cm in a healthy adult. Its weight can be 150-200 g. Generally, the outer region of the spleen is the capsule made up of fibrous and elastic connective tissue. The two functional zones of the spleen are the red and the white pulp. A marginal sinus separates the red pulp from the white pulp. Here, the red pulp is composed of sinuses filled with blood. It also contains reticular fibers. In general, the red pulp stores over half of the total monocytes of the body. These monocytes are responsible for moving into the injured tissues to promote tissue healing by becoming macrophages and dendritic cells. However, the main function of red pulp is the mechanical filtration of red blood cells.

In contrast, the nodules in the white pulp are Malpighian corpuscles, which are composed of lymphoid follicles with B lymphocytes and periarteriolar lymphoid sheaths rich in t lymphocytes. Therefore, the main function of the white pulp is to be in contact with pathogenic antigens, promoting the maturation of lymphocytes.

Similarities Between Lymph Node and Spleen

• Lymph node and spleen are two types of secondary lymphoid organs found in the immune system of vertebrates.
• They can be divided into compartments called lobules.
• Both host B- and T-lymphocytes ready to capture antigens.
• Also, their main function is to filter pathogens allowing the lymphocytes to be in contact with their antigens.

Difference Between Lymph Node and Spleen

Definition

A lymph node refers to each of a number of small swellings in the lymphatic system where lymph is filtered and lymphocytes are formed while spleen refers to an abdominal organ involved in the production and removal of blood cells in most vertebrates and forming part of the immune system. Thus, this is the fundamental difference between lymph node and spleen.

Significance

A lymph node is a small mass of tissues located along the lymphatic system while spleen is an organ found in vertebrates. Hence, this is the main difference between lymph node and spleen.

Size

Also, the size of a lymph node can range from a few millimeters to 1-2 cm while spleen is the largest organ found in the lymphatic system.

Structure

Moreover, their structure is another important difference between lymph node and spleen. A lymph node is composed of an outer cortex and inner medulla while the spleen is composed of red pulp and white pulp.

Function

Furthermore, the functional difference between lymph node and spleen is that the lymph nodes filter lymph to capture pathogens while spleen filters blood to capture pathogens.

Conclusion

The lymph node is a small mass of tissues found along the lymphatic vessels in vertebrates. The main function of lymph nodes is to filter lymph to capture pathogens. In comparison, the spleen is an organ responsible for filtering pathogens in the blood. Both lymph nodes and the spleen host B- and T-lymphocytes, allowing them to make contact with pathogenic antigens. Therefore, both lymph node and spleen are two types of secondary lymphoid organs. However, the main difference between lymph node and spleen is their structure and function.

References:

1. “Lymph Nodes.” Kenhub, Kenhub, 14 Feb. 2019, Available Here.
2. Hoffman, Matthew. “The Spleen (Human Anatomy): Picture, Location, Function, and Related Conditions.” WebMD, WebMD, Available Here.

Image Courtesy:

1. “Illu lymph node structure” By SEER (archived version)U.S. National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) Program (Public Domain) via Commons Wikimedia  
2. “Diagram of a lymph node CRUK 022” By Cancer Research UK – Original email from CRUK (CC BY-SA 4.0) via Commons Wikimedia    
3. “Illu spleen” (Public Domain) via Commons Wikimedia