Lymph node

Your body has tiny helpers.

They are shaped like beans. They are found all over your body. Many are near your neck and arm.

These helpers act like filters. They catch bad things in your body. This helps you stay well. They use special cells to fight.

Sometimes these helpers get big. They can feel sore or firm. This can happen when you are sick. It is your body working hard.

Your body has many tiny helpers called lymph nodes.

Most are shaped like beans or ovals. They are usually small, about 15 mm long. You can find them all over your body. Many are in your neck, under your arms, or near your groin.

Lymph nodes act like filters. They clean a liquid called lymph. This liquid flows through tubes called lymphatic vessels. The lymph enters the node through many small tubes. It moves through spaces inside the node. These spaces are called sinuses.

The lymph then leaves through one main tube. This exit is called the hilum.

Inside the node, special white blood cells wait. These are called lymphocytes. They include B cells and T cells.

B cells make antibodies to fight germs. T cells help catch bad things. The nodes catch tiny pieces called antigens. These antigens come from bacteria or other germs. When nodes fight germs, they may swell. This is called lymphadenopathy. Swollen nodes can feel firm or tender.

Your body has many tiny helpers called lymph nodes.

These small organs are part of your immune system. They act like important filters for your body. They catch foreign particles like cancer cells. This helps keep you healthy and strong. Most lymph nodes are shaped like a kidney.

They usually measure about 15 mm on their long side. They can range from 2 mm to 25 mm in size.

Lymph nodes work by filtering a liquid called lymph.

This liquid flows through many small tubes called afferent vessels. The lymph enters the node on its rounded side. It first moves into a space called the subcapsular sinus. Then, it flows through the cortex into medullary sinuses. Finally, the lymph leaves through an efferent vessel. This exit happens at a spot called the hilum. This slow flow gives your body time to react.

Inside the node, many special cells wait to help. These cells are called lymphocytes.

There are two main types of these white blood cells. B cells live mostly in the outer cortex. They can grow into germinal centers to make antibodies. T cells live in a deeper part called the paracortex. These cells work with dendritic cells to find germs. The middle part is called the medulla. It contains plasma cells and macrophages to help fight.

An adult human has about 450 lymph nodes.

They are found all throughout your body. You can often feel some of them if they swell. For example, you can feel nodes in your neck. You can also feel them under your arms. Other nodes are located near your groin crease. Some are deep inside, like the paraaortic lymph nodes. There are no lymph nodes in your central nervous system.

Sometimes, lymph nodes can become swollen or enlarged.

Doctors call this condition lymphadenopathy. The nodes might feel firm or even tender to touch. This swelling can happen during a mild throat infection. It can also happen during more serious diseases like cancer. Doctors look at the nodes to help stage cancer. This helps them decide the best way to treat it. Knowing the state of your nodes helps predict your prognosis.

A lymph node is a small, kidney-shaped organ within the lymphatic system. It serves as a critical component of the adaptive immune system. These organs act as biological filters for the body. They catch foreign particles, such as bacteria or cancer cells, to prevent them from spreading. While they filter many things, they do not have a detoxification function.

Each lymph node is enclosed in a fibrous capsule made of collagenous connective tissue. This capsule extends into the interior of the node to form structures called trabeculae. These trabeculae divide the node into different sections. The internal substance is organized into two main regions: the outer cortex and the inner medulla.

The cortex is the outer layer located just beneath the capsule. The medulla is the central part of the node. On the concave side of the node, there is an indent called the hilum. This is where blood vessels enter and leave, and where lymphatic vessels exit.

The movement of fluid through the node follows a specific path. Lymph enters the convex side through multiple afferent lymphatic vessels. Once inside, the fluid first moves into a space called the subcapsular sinus. From there, it flows into cortical sinuses within the cortex. After traversing the cortex, the lymph collects in the medullary sinuses. Finally, the fluid drains into efferent lymphatic vessels. These vessels carry the lymph away from the node through the hilum. There is usually only one efferent vessel, which is fewer than the many afferent channels. This design slows the flow of lymph, providing more time for immune cells to react to potential threats.

Inside the node, specialized white blood cells called lymphocytes perform immune tasks. The cortex is divided into an outer part and a deeper part called the paracortex. The outer cortex contains follicles made of B cells. When these B cells are activated, they may develop into a germinal center. The paracortex is the deeper region that mainly consists of T cells. In this area, T cells interact with dendritic cells. The medulla contains fewer cells than the cortex. It holds large blood vessels, sinuses, and medullary cords. These cords contain plasma cells, which secrete antibodies, as well as macrophages and B cells.

The immune response relies on how these cells interact with antigens. Antigens are molecules found on bacterial cell walls or other foreign substances. Dendritic cells act as antigen-presenting cells. They take up antigens and carry them into the lymph node to show them to T cells. If a T cell has the right receptor, it becomes activated. B cells acquire antigens directly from the lymph. When a B cell binds to its specific antigen, it is activated. It can then multiply to become a plasma cell that produces antibodies. These antibodies target specific antigens to stimulate a full immune response. If a B cell is not stimulated, it undergoes apoptosis, or programmed cell death.

An adult human has approximately 450 lymph nodes distributed throughout the body. They are most concentrated within the trunk. Some groups are easy to find, such as the cervical nodes in the neck, the axillary nodes under the arms, and the inguinal nodes near the groin. Other nodes, like the paraaortic or tracheobronchial nodes, lie deep near major structures. Interestingly, there are no lymph nodes in the central nervous system. However, the central nervous system is connected to the nodes via sympathetic nerves. These nerves help regulate how immune cells move and how antibodies are secreted.

The size of a lymph node varies by location and individual. On average, a node is about 15 mm long, but they can range from 2 mm to 25 mm. Specific locations have different typical sizes. For example, inguinal nodes are often 10 to 20 mm, while nodes in the upper abdominal region, like the portacaval space, are usually around 10 mm. When lymph nodes become swollen or enlarged, the condition is called lymphadenopathy. Enlarged nodes can feel firm or tender. This swelling can result from mild infections or serious diseases like cancer. Because of this, doctors use the condition of lymph nodes to help with cancer staging. This helps determine a patient's prognosis and the best treatment to use.