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    Related Topics

    From Lymphatic System

    Thoracic Duct
    Main lymphatic duct draining most of the body.
    Deep Cervical Lymph Nodes
    Located along internal jugular vein; receive lymph from head and neck.
    Iliac Lymph Nodes
    Include external, internal, and common iliac nodes.
    Pretracheal Nodes
    Located anterior to the trachea.
    Peyer’s Patches
    Lymphoid nodules in the small intestine.
    Superficial Cervical Lymph Nodes
    Drain superficial structures of the head and neck.
    Pectoral Axillary Nodes
    Located along the anterior chest wall.
    Preaortic Nodes
    Located in front of the aorta.
    BALT
    Bronchus-associated lymphoid tissue.
    Para-aortic Lymph Nodes
    Drain abdominal viscera and lower limbs.
    Tubal Tonsils
    Near openings of the auditory tubes.
    Red Bone Marrow
    Produces lymphocytes; site of B-cell maturation.
    Retroaortic Nodes
    Located behind the aorta.
    Submental Lymph Nodes
    Drain the floor of the mouth and central lower lip.
    Inguinal Lymph Nodes
    Drain the lower limbs and external genitalia.
    Mastoid Lymph Nodes
    Drain the posterior scalp and ear.
    Cisterna Chyli
    Dilated sac at the start of the thoracic duct.
    Axillary Lymph Nodes
    Drain the upper limbs and chest wall.
    MALT
    Mucosa-associated lymphoid tissue.
    SALT
    Skin-associated lymphoid tissue.
    Central Axillary Nodes
    Located centrally in the armpit.
    Lateral Axillary Nodes
    Located along the humerus in the axilla.
    Palatine Tonsils
    Located on each side of the oropharynx.
    Waldeyer’s Ring
    Ring of lymphoid tissue surrounding the naso- and oropharynx.
    Right Lymphatic Duct
    Drains right upper quadrant of the body.

    Lymph Nodes

    Reviewed by our medical team

    Small structures that filter lymph and store immune cells.

    1. Overview

    Lymph nodes are small, encapsulated, bean-shaped organs of the lymphatic system distributed throughout the body. They act as biological filters, screening lymph (a clear fluid derived from interstitial fluid) for foreign substances, pathogens, and cancer cells. Lymph nodes are vital for initiating immune responses and are essential in maintaining immune surveillance and homeostasis. There are approximately 500–700 lymph nodes in the adult human body, grouped into superficial and deep clusters in areas like the neck, axilla, thorax, abdomen, and groin.

    2. Location

    Lymph nodes are located along the course of lymphatic vessels and are strategically placed to monitor lymph from specific regions. Major groupings include:

    • Cervical lymph nodes: Drain the head and neck

    • Axillary lymph nodes: Drain the upper limbs, chest, and breasts

    • Inguinal lymph nodes: Drain the lower limbs, genitalia, and lower abdominal wall

    • Thoracic lymph nodes: Drain lungs, heart, and mediastinum

    • Abdominal and pelvic lymph nodes: Drain gastrointestinal and urogenital organs

    Each node is positioned to intercept and filter lymph before it is returned to the bloodstream via the subclavian veins.

    3. Structure

    Lymph nodes are encapsulated organs composed of lymphoid tissue with a distinct internal architecture, allowing efficient filtration and immune processing:

    • Capsule: Dense connective tissue that surrounds the node and sends trabeculae inward.

    • Cortex: Outer layer containing lymphoid follicles with germinal centers rich in B cells.

    • Paracortex: Located between cortex and medulla; contains T cells and dendritic cells.

    • Medulla: Contains medullary cords (with plasma cells and macrophages) and sinuses for filtered lymph to exit.

    • Afferent lymphatic vessels: Enter the convex surface and carry lymph into the node.

    • Efferent lymphatic vessels: Exit at the hilum and drain filtered lymph away from the node.

    4. Function

    Lymph nodes perform multiple critical functions in the immune and lymphatic systems:

    • Lymph filtration: Remove pathogens, foreign particles, and cancer cells from lymph before it reaches the bloodstream.

    • Immune activation: Act as sites where antigens are presented to lymphocytes, initiating adaptive immune responses.

    • Antibody production: Plasma cells within the node secrete antibodies into lymph and blood.

    • Immune cell trafficking: Coordinate migration of lymphocytes and antigen-presenting cells (e.g., dendritic cells) within the node.

    5. Physiological Role(s)

    Lymph nodes play essential roles in systemic physiology and immunity:

    • Defense against infection: Act as sentinels that detect and respond to infectious agents.

    • Homeostasis of tissue fluids: By filtering lymph and returning it to the venous system, they prevent tissue edema.

    • Surveillance for neoplasia: Lymph nodes are capable of recognizing and responding to early tumor spread.

    • Central hubs for immune memory: Facilitate generation and retention of memory B and T cells after exposure to antigens.

    6. Clinical Significance

    Lymphadenopathy

    Lymphadenopathy refers to enlargement of lymph nodes, which may be due to:

    • Infections: Viral (e.g., EBV), bacterial (e.g., tuberculosis), fungal, or parasitic infections.

    • Inflammatory/autoimmune conditions: Sarcoidosis, rheumatoid arthritis, systemic lupus erythematosus.

    • Malignancy: Either primary (e.g., lymphoma) or secondary (metastasis from carcinoma).

    Enlarged lymph nodes may be tender, mobile, and soft (typically in infection), or firm, fixed, and non-tender (suggestive of malignancy).

    Sentinel Lymph Nodes

    A sentinel lymph node is the first node to receive lymphatic drainage from a tumor. Its biopsy helps determine if cancer has spread and is widely used in the staging of:

    • Breast cancer

    • Melanoma

    • Gynecologic and gastrointestinal cancers

    Lymphadenectomy

    Surgical removal of lymph nodes is performed to:

    • Stage and treat cancer (e.g., axillary dissection in breast cancer)

    • Remove infected or necrotic nodes (e.g., in TB or necrotizing lymphadenitis)

    Diagnostic Techniques

    • Palpation: First-line clinical exam for assessing lymphadenopathy

    • Ultrasound and CT/MRI: Imaging for size, location, and internal structure

    • Fine needle aspiration (FNA): Used to obtain cytology samples

    • Excisional biopsy: Performed when malignancy or lymphoma is suspected

    Immunological Disorders

    In immunodeficiency states or HIV/AIDS, lymph nodes may initially enlarge due to hyperactivation, followed by atrophy and architectural collapse over time, indicating systemic immune compromise.

    Did you know? The lymphatic system helps the body prevent the spread of cancer by filtering out cancer cells from the bloodstream.