Lymph Nodes

A lymph node or lymph gland belongs to the lymphatic system and is an oval shaped or kidney-shaped organ, and it also belongs to the adaptive immune system, which are widely present all over the body.

Lymphatic vessels connect them as a part of the circulatory system. In the lymphatic system the lymph node is a secondary lymphoid organ. A lymph node is surrounded by a fibrous capsule and is made up of an outer cortex and an inner medulla.

Acting as sieves for foreign particles and cancer cells, lymph nodes are crucial for the proper working of the immune system. B and T lymphocytes and other white blood cells are mainly found at lymph nodes. Lymph nodes do not detoxify, it is mainly done by the liver and kidneys.

B and T lymphocytes

The major cellular components of the adaptive immune response are T cells or thymus cells and B cells a.k.a. bone marrow or bursa derived cells. T cells are related to cell-mediated immunity, while humoral immunity relating to antibodies is B cells dominion. At the time of a process known as antigen presentation, the T cells and B cells recognize particular antigens.

The cells generate specific responses that are designed to eliminate specific pathogens or pathogen-infected cells excellently on the detection of an intruder.

• B cells act in response towards pathogens by creating huge quantities of antibodies which then counteract foreign substances like bacteria and viruses.
• Against pathogens:
  • Some T cells known as T helper cells create cytokines which direct the immune response.
  • While other T cells known cytotoxic T cells create toxic granules that have powerful enzymes which kill pathogen-infected cells.

Structure

Lymph nodes interrupt the path of lymphatic vessels and are made up of components of the body’s defense system, like clusters of lymphocytes and macrophages.

• They act as complex screening organs which snare and phagocytize particulate matter in the lymph which permeates through them.
• Also, they identify and protect against foreign antigens that are also transported via the lymph.
• Cells that drift away from primary tumors and enter lymphatic vessels often inhabit and grow as secondary tumors in lymph nodes, as lymph nodes are capable filters and flow of lymph through them is slow.

Capsule

The lymph node capsule is made up of:

• Dense irregular connective tissue.
• Plain collagenous fibers.

From its internal surface various membranous processes or trabeculae are created. They go inward, circulating toward the center of the node, for around one-third or one-fourth of the space in the middle of the circumference and the center of the node.

Subcapsular sinus

The space in the middle of the capsule and the cortex which enables the free movement of lymphatic fluid is called the subcapsular sinus a.k.a. lymph path, lymph sinus or marginal sinus and it also consist of few lymphocytes.

• It is constant with the similar lymph sinuses which surround the trabeculae.
• The lymph node is made up of a network of fibers called reticulum which has white blood cells trapped in it.
• Lymph sinuses are zones having few cells inside the network; they are surrounded by reticular cells, fibroblasts along with fixed macrophages.

Function

The subcapsular sinus channels towards the trabecular sinuses and afterwards the lymph runs into the medullary sinuses.

Clinical Significance

The subcapsular sinus is the most probable site in a lymph node where the initial appearances of a metastatic carcinoma would develop. So, it is clinically valuable.

Cortex

The exterior part of the node, inferior to the capsule and the subcapsular sinus is called the cortex of the lymph node.

• Paracortex is the external superficial part and a deeper part of cortex.
• The outer cortex is made up of the B cells set as follicles, which may create a germinal center when confronted by an antigen.
• The deeper paracortex is primarily made up of the T cells. Here the T-cells mainly connect with dendritic cells; also the reticular network is condensed.

Medulla

• The medulla is made up of large blood vessels, sinuses and medullary cords which are made up of antibody-secreting plasma cells.
• The medullary cords are cords of lymphatic tissue, and are made up of plasma cells, macrophages, as well as B cells.
• The medullary cords are divided by the medullary sinuses or sinusoids which are vessel-like spaces.
• From cortical sinuses lymph flows into the medullary sinuses, and into the efferent lymphatic vessel. Generally there is only one efferent vessel, yet there may be two sometimes.
• Medullary sinuses consist of immobile macrophages known as histiocytes and reticular cells.

Functions

• Lymph nodes are capable screening organs and have an internal structure like a honeycomb of reticular connective tissue filled with lymphocytes.
• These lymphocytes counter bacteria, viruses, and other biological/pathogenic cells in order to destroy them.
• Lymph nodes drain definite areas.
• Lymph nodes are activated when infection arises inside a drainage area.

Palpation

Lymph nodes are abundant and can be palpated in the axilla, the groin, femoral area and the neck.

Unpalpable deep sites include sites related to:

• The trachea and bronchi in the thorax.
• The aorta and its branches in the abdomen.

Clinical Significance

Diagnosis – General

Lymph nodes that drain areas that are infected or have other types of disease can show physical changes. Such changes can help in order to detect pathologic changes or in order to track range of disease.

A number of zones are related to groups or a particular profusion of lymph nodes in the body. Nodes in many of these regions drain lymph from the body’s surface, the digestive system, or the respiratory system which have high-risk for the entrance of Foreign pathogens/Antigens.

Swelling/Swollen Lymph Nodes

Lymph nodes may get swollen due to:

• Ear infection
• Cold or flu
• Sinus infection
• HIV infection
• Infected tooth
• Mononucleosis
• Dermatological infection
• Hodgkin’s disease
• Leukemia
• Metastasized cancer
• Non-Hodgkin’s lymphoma
• Measles
• Tonsillitis
• Toxoplasmosis
• Tuberculosis
• Cat scratch fever
• Ear infections
• Gingivitis

Swollen lymph nodes or the condition causing them are known as lymphadenopathy.

• Swollen lymph nodes may be observed as a result of lymphoma, like enlarged tonsils or such as total enlargement of nodes.
• Swollen lymph nodes may cause pain or cause other symptoms like trouble in swallowing or in breathing.
• When very large they may compress on a blood vessel.
• Swelling can arise in a single node, a local area, or can be extensive.

Cancer

Both primary cancers of lymph tissue and secondary cancers affecting other part of the body can affect lymph nodes.

• Generally due to tumours cells that have metastasized into the node in many parts of the body local cancer can make lymph nodes to enlarge.
• Primary lymph tissue cancers are known as lymphomas and involve Hodgkin lymphoma as well as non-Hodgkin lymphoma.
• A wide range of symptoms can be created through cancer of lymph nodes, from painless long-term gradually developing inflammation to sudden, swift expansion in days or weeks.
• A crucial portion in the diagnosis and treatment of cancer is often the involvement of lymph nodes.

Lymph nodes may be imaged or even surgically removed as part of the treatment or diagnosis for cancer.

Auto immune diseases

Common markers in auto immune diseases are Lymph Nodes. The most affected sites of auto immune diseases are lymph nodes. Stimulated nodes exhibit can symptoms like swelling, expansion as well as pain.

An autoimmune disease is a condition arising from an abnormal immune response to a normal body part. Since, there are no less than 80 types of autoimmune diseases; nearly any body portion can be affected. Symptoms often vary; common symptoms consist of low grade fever and feeling tired constantly.

Some autoimmune diseases run are hereditary like lupus. Infections or other environmental factors may cause certain instances.

Diseases that are normally regarded as autoimmune consist of:

• Celiac disease
• Diabetes mellitus type 1
• Graves’ disease
• Inflammatory bowel disease
• Multiple sclerosis
• Psoriasis
• Rheumatoid arthritis
• Systemic lupus erythematosus

Treatment is according to the type and seriousness of the disorder:

• Non-steroidal anti-inflammatory drugs (NSAIDs) and immunosuppressants.
• Intravenous Immunoglobulin.
• While treatments do not typically cure the disease, they generally decrease symptoms.