Lymph Nodes: Functions, Diagnosis and Treatment

Overview 

Lymph nodes, small bean-shaped structures found throughout the body, play a vital role in your overall health. Acting as filters, they help trap harmful substances and fight off infections, making them essential components of the immune system.

The lymphatic system plays a crucial role in supporting immunity and maintaining fluid balance. It serves as a key component of the immune system, defending the body against infections. Additionally, it collects excess fluid and waste products, returning them to the bloodstream. 

Anatomy of Lymph Nodes

Lymph nodes vary in size ( 1-2 cm) depending on their location and are enclosed by connective tissue capsules. Specialised blood vessels bring lymphocytes into the lymph node, where B and T lymphocytes bind to receptors and become activated.

Lymph nodes are deemed pathological (infected) if:

• They lose their oval shape
• There is a thickening of their cortex (inner layer) 
• They are persistently enlarged

Structure of Lymph Nodes

Each lymph node is divided into the following regions:

• Capsule: The outermost layer made of dense connective tissue and collagen fibres, with minute rods or trabeculae extending towards the centre.
• Subcapsular Sinus: The space through which lymph is transported.
• Cortex: Located below the subcapsular sinus, it consists of an outer B-cell layer and an inner layer called the paracortex, which is the T-cell layer.
• Medulla: The innermost layer containing blood vessels, sinuses and medullary cords. The cords contain plasma cells, B-cells and macrophages. The sinuses receive lymph from the trabeculae and drain it into the outgoing lymphatic vessels.

Location of Lymph Nodes in the Body

Lymph nodes are located where major blood vessels meet and are distributed throughout the body along the lymphatic pathways. Adults typically have around 800 nodes, predominantly found in the following areas:

• Neck (cervical lymph nodes)
• In the armpits (axillary nodes)
• Above the collar bone (supraclavicular nodes)
• Chest (mediastinal nodes)
• Groin (inguinal nodes)
• Behind the abdomen (retroperitoneal lymph nodes)
• Lower abdominal region (pelvic nodes)
• Knees (popliteal nodes)

Lymphatic Vessels

Afferent (incoming) lymphatic vessels drain into each lymph node, and efferent (outgoing) lymphatic vessels carry filtered lymph back into the lymphatic circulation.

The lymph returns to the bloodstream via the superficial and deep lymphatic vessels. These vessels drain into the right lymphatic duct and the thoracic duct. The right lymphatic duct drains the upper right quadrant of the body, returning lymph via the right subclavian vein. The thoracic duct collects lymph from the rest of the body into the left subclavian vein. Lymph moves along the vessels due to muscle contractions, and valves are present to prevent the backflow of lymph.

Function of Lymph Nodes

The primary function of lymph nodes is to filter lymph, the extracellular fluid that has leaked from blood capillaries, and return it to circulation. This filtration process helps maintain fluid balance and prevents fluid imbalance that could be life-threatening. Additionally, lymph nodes play a crucial role in activating immune cells like T-cells and B-cells, enabling them to fight infections.

Role of Lymph Nodes in the Immune System

Lymph nodes serve as important hubs for lymphocytes to interact, detect threats, and mount targeted immune defences. Lymphocytes, including B-cells and T-cells, are major types of white blood cells involved in the immune response. B-cells produce antibodies that attach to antigens and destroy them, while T-cells identify and destroy infected or cancerous cells. These lymphocytes are produced and matured in primary lymphoid organs like the thymus gland and bone marrow. Secondary lymphoid organs, such as lymph nodes and spleen, play a role in further differentiating lymphocytes.

How Lymph Nodes Filter Lymphatic Fluid?

Lymph nodes act as filters for lymphatic fluid, removing impurities and harmful substances. As lymph flows through the nodes, specialized immune cells called lymphocytes detect and destroy foreign particles, microbes, and damaged cells. This filtration process helps purify the lymphatic fluid before it returns to the bloodstream, supporting immune function.

Lymphocyte Activation and Proliferation

In the cortex of the lymph node, resting/inactivated lymphocytes reside until they come into contact with foreign antigens. The outer cortex layer harbours B-cells, dendritic cells and macrophages, while the inner cortex layer houses T-cells. Upon activation, B-cells differentiate into plasma cells within the medulla, producing antibodies. Activated T-cells can become helper T cells or cytotoxic T lymphocytes. These activated lymphocytes then enter the lymphatic circulation through the efferent vessel, ultimately proliferating and exerting their functions throughout the body.

Common Conditions Affecting Lymph Nodes

When the body undergoes attack by foreign cells, microbes or even cancer cells, lymph nodes are also affected, in one of the following ways: 

Lymphadenopathy: Swollen Lymph Nodes

Lymphadenopathy is an enlargement or a change in the usual character of a lymph node. It is not a disease, but a symptom of an infectious or noninfectious condition. Swollen lymph nodes could be mobile or fixed (to an internal structure), painful or painless or localised or generalised.

Lymphadenitis: Inflammation of Lymph Nodes

Lymphadenitis refers to inflamed and sore lymph nodes caused by an infection originating elsewhere in the body. Normally small and firm, infected lymph nodes can enlarge, become tender and are palpable during a physical examination. Lymphadenitis is often accompanied by pain, fever and skin changes, with or without pus. Inflammation of the lymphatic vessels, with or without involvement of the lymph nodes, is known as lymphangitis.

Lymphoma: Cancer of the Lymphatic System

Lymphoma is a cancer that starts in the lymphatic system cells. There are two primary types: Hodgkin Lymphoma, often curable, and Non-Hodgkin Lymphoma, which varies in prognosis depending on the specific subtype.

Other Conditions Affecting Lymph Nodes

Cancer originating from other organs can affect lymph nodes, commonly through solid tumours. Solid tumours are abnormal masses of tissue without cysts or fluid, occurring in bones, soft tissue or skin. Cancer cells typically reach nearby lymph nodes before spreading further. 

Lymphoedema, a condition of chronic swelling or oedema, may occur when cancer surgery involves the removal of affected lymph nodes, leading to lymph buildup in the surrounding tissues.

Diagnosis and Treatment of Lymph Node Disorders

Normal lymph nodes are usually small and inconspicuous but can become noticeable due to infection, inflammation or cancer. If located near the body's surface, they may be felt or seen.

Diagnostic Tests for Lymph Node Disorders

Enlarged lymph nodes deep in the body due to infection or cancer are not palpable or visible. Diagnosis requires blood tests and imaging techniques such as X-ray, Computed Tomography (CT) or Positron Emission Tomography (PET). Lymph nodes near the primary site of cancer may be biopsied to confirm malignancy.

Treatment Options for Lymph Node Disorders

The treatment for lymph node disorders depends on the general health and the symptoms present. Usually, one or many of the following may be needed:

• NSAIDs for pain
• Antibiotics 
• Medications to treat the condition that caused swollen lymph nodes
• Cancer treatment involving chemotherapy, radiation or immunotherapy
• Surgery 

Medications Used to Treat Lymph Node Disorders

When swollen lymph nodes are limited to a specific region, the cause is usually a viral infection, and no treatment may be needed. Such nodes will gradually shrink back to normal size. 

Generalised lymphadenitis usually means a more serious infection like:

• Autoimmune disorders like lupus, which requires corticosteroids and hydroxychloroquine 
• Bacterial infections like dental abscess, Lyme disease and typhoid fever, which are treated with antibiotics like doxycycline, amoxicillin and ciprofloxacin
• Sexually transmitted infections like syphilis, which are treated with penicillin 

How to Keep Your Lymph Nodes Healthy?

A few simple things that can be done to take care of lymph nodes are:

• Maintain a balanced diet
• Engage in regular physical activity
• Practice good hygiene
• Avoid exposure to toxins and pollutants
• Manage stress levels through relaxation techniques like meditation or yoga.
• Seek prompt medical attention if you notice any abnormal swelling or changes in your lymph nodes

Lifestyle Changes to Promote Lymphatic System Health

Lymph node enlargement cannot be prevented, as it is a response to infections or other conditions. To prevent common infections like the flu, practice good hygiene by 

• Washing hands regularly, 
• Avoiding contact with sick individuals and 
• Wearing a mask in crowded places.

Diet and Nutrition for a Healthy Lymphatic System

A few general guidelines can help in maintaining overall health and immune function:

• Drinking enough water promotes detoxification
• Eating plenty of fruits, vegetables, whole grains and healthy fats 
• Including foods rich in omega-3 fatty acids, such as fatty fish
• Limiting processed foods and sugary snacks

Exercise and Lymphatic System Health

• Regular physical activity stimulates lymph flow and boosts circulation.
• Brisk walking, jogging and swimming can be combined with strength training
• The lymphatic system can be stimulated by stretching, bouncing on a trampoline and specialised massages 
• Sitting or standing in one position for prolonged periods should be avoided.

Conclusion

A healthy lymphatic system plays an important role in maintaining good overall health. The goal is to reach an ideal body weight through a balanced diet and regular exercise as excess weight can put additional strain on the lymphatic system.

An early diagnosis and prompt treatment are of prime importance in preventing complications. 

FAQs

What Causes Lymph Nodes to Swell?

Infections, such as viral or bacterial infections, are the most common cause of lymph node swelling. Other causes can include immune system disorders and cancer.

Can Lymph Nodes be Removed?

Yes. Lymph nodes can be surgically removed through a procedure called lymphadenectomy. It may be done as part of the treatment for cancer to prevent the spread of cancer cells. It can also be performed to diagnose and treat lymphatic system disorders.

What are The Signs of Lymph Node Cancer?

Some signs of lymph node cancer are:

• Nodes larger than 1cm in diameter
• Nodes that are painful, hard and grow rapidly
• Swollen lymph nodes in the neck

Can Stress Affect Lymph Nodes?

Chronic stress can affect lymphatic function. It can be managed with stress-reducing activities like yoga, meditation, deep breathing exercises or by pursuing hobbies.

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