What is Lymph Node? Structure, Histology & Functions

A Lymph node is an oval-shaped tissue in our body that plays an important role in fighting infection and cancer. Lymph node histology can enlighten things properly which is described below.

The human body contains an extensive lymphatic system which consists of lymph nodes and vessels. Lymph vessel carries clear fluid which is collected from tissue in the whole body. Lymph contains cell waste like bacteria, virus and cancer cells.

Lymph nodes work as a filter along the lymphatic system of your body. They trap the bacteria, virus, cancer cells and unwanted substances and safely eliminate from the human body.

The Lymph nodes are scattered throughout the human body and find in the groups such as groin, neck, pelvic, armpit and abdomen. In the area like the neck, a lymph node is located superficially. It feels like a pea or small bean. But in the areas like abdomen or chest lymph nodes are located deeper and cannot be felt.

In the areas like the abdomen/chest lymph nodes are located deeper and cannot be felt. An enlarged lymph node is the sign of infection, cancer or a disease that affects the immune system. Shotty lymph nodes are another thing to take care of as it affects the body.

The nodes which are immobile, hard, non-tender and persistently enlarged are suspicious for cancer and must be evaluated by a physician. In the presence of a cancer cell in a lymph node, they may spread from the primary tumor-like breast that spread to lymph nodes in the armpit. When they organize in a lymph node it is called lymphoma.

Lymph Node Structure

Lymph nodes are small bean-shaped glands located along the lymphatic system. Every lymph node is divided into two regions a capsule and cortex. Classically a lymph node is described as an encapsulated kidney-shaped structure with various afferent vessels piercing its surface.

It is a collection of lymphoid tissue which is enclosed in a connective tissue capsule and lying along the lymphatic stream. From the capsule parts of tissue pass into the substance of the node and called as the connective tissue trabeculae.

In the human body lymphatic nodes, the trabeculae are difficult to define. As they have repeated branches and reticular tissue of the node, compose of ill-defined sinuses, the meshes that are filled up with lymphoid cells in different stages of development.

Lymph Node Histology

lymph node histology diagram
Lymph Node Histology Diagram

 The histology is the form of the structure under the microscope. It is also called microscopic anatomy as opposed to gross anatomy. In this, the structure can be observed with a naked eye.

 A Lymph node histology diagram shows the pathways that lymphocytes can take inside and outside of the lymph node. Most of the lymphocytes enter a lymph node through blood vessels and about 10% through lymph. This area of lymph contains lots of T-cells and antigen-presenting dendritic cells.

There are 400 to 450 lymph nodes are found in a human body. They are found along the lymphatic vessels, that carries fluid from the interstitial space into the main circulation.

Histologically the nodes can be divided into an outer part, the cortex and an inner part of the medulla.

  • Cortex

Lymphoid tissues remain scattered in a node but in the cortex, they are found collected. The lymphoid nodules which vary from .35 to 1.00 mm in diameter. These nodules remain arranged parallel to the surface, like two or three layers deep.

Every lymph nodule is pierced by a small blood vessel that shows a less dense area at its center, that takes the lighter strain. Surrounding this lighter area there and a wider area which is packed with lymphocytes.

  • Paracortex

This is deep to the cortical layer. It is a mixture of the superficial cortex and deep medulla. The main distinguishing features are a large number of T lymphocytes and the absence of lymphoid nodules. Paracortex has unique venules called as High Endothelial Venules.

Most of the lymphocytes enter the lymph node through these channels. They are made up of cuboidal endothelium which is fitted apically with integrins and glycoproteins.

  • Medulla

This is the deepest layer of a lymph node which subdivided functionality and histology into two other regions one is medullary cords and another is sinuses. The cords are populated by plasma cells, B-cells and T-cells. These cells are arranged in a cord like projecting extending centrally from the paracortex.

The central or lighter zone is called the germinal center or secondary nodule. The peripheral area is called the cortical/primary nodule.

 

Lymph Node Function

Lymph nodes have two major functions in our body. They filter lymph and assist the immune system of the body. Lymph is a clear fluid which comes from blood plasma exists in the blood vessels at capillary beds.

When a person is found with cancer a lymph node is evaluated in the first place. After that, the journey starts to explore the setup home elsewhere in the body.

A lymph node has a crucial role when it comes to fighting infections. They trap virus and bacteria so that T cell can attack a type of T cell presents the invader to B cell so the B can make antibodies against the invader.  This is the way lymph node place where the immune cell can communicate and work together.

Functions of the lymphatic system:

1. Drain fluid back into the bloodstream

The main function of the lymphatic system is to collect the excess fluid surrounding the body’s tissues and organs and return it to the bloodstream. In case lymphatic system unable to drain excess fluid from the tissue, the lymph fluid would build up in the body and cause swelling.

2. Filters the blood in your body

It filters the blood, removes old red blood cells and replaces them with new blood cells that are made in the bone marrow.

3. Remove toxins and other impurities

A lymphatic system helps to remove toxins and other impurities from the body. The impurities include carbon dioxide, sodium and other byproducts of cellular feeding on oxygen, mineral, and nutrients. It also helps to remove the impurities and dispose of them through perspiration, bowel movements, urine, and breathing.

4. Fights against infections

The lymphatic system helps your body to defend against illness due to germs, bacteria, virus, and fungi. Builds the immunity by making special white blood cells that produce antibodies which are helpful for immune responses and defend the body against various diseases.

It is important to keep your lymphatic system healthy to prevent illness and other important body system functioning. Drink plenty of water, eat healthy food including healthy fats, exercise daily, avoid pollutants and learn to manage stress through yoga or meditation.

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