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    Related Topics

    From Lymphatic System

    Inguinal Lymph Nodes
    Drain the lower limbs and external genitalia.
    Lingual Tonsils
    Located at the base of the tongue.
    Lymph Nodes
    Small structures that filter lymph and store immune cells.
    Pretracheal Nodes
    Located anterior to the trachea.
    Occipital Lymph Nodes
    Drain the back of the scalp.
    MALT
    Mucosa-associated lymphoid tissue.
    Tracheobronchial Nodes
    Drain lungs and bronchi.
    Peyer’s Patches
    Lymphoid nodules in the small intestine.
    Thoracic Duct
    Main lymphatic duct draining most of the body.
    Intestinal Trunk
    Drains lymph from the intestines.
    GALT
    Gut-associated lymphoid tissue.
    Deep Cervical Lymph Nodes
    Located along internal jugular vein; receive lymph from head and neck.
    Mesenteric Lymph Nodes
    Drain the intestines and abdominal structures.
    Parotid Lymph Nodes
    Drain the lateral face and scalp.
    Lymphatic Collecting Vessels
    Carry lymph through lymph nodes.
    Submandibular Lymph Nodes
    Drain the face, mouth, and pharynx.
    Central Axillary Nodes
    Located centrally in the armpit.
    Subscapular Axillary Nodes
    Located along the posterior chest wall.
    Jugular Trunk
    Drains lymph from the head and neck.
    Pectoral Axillary Nodes
    Located along the anterior chest wall.
    Retroaortic Nodes
    Located behind the aorta.
    Popliteal Lymph Nodes
    Drain the foot and leg.
    Palatine Tonsils
    Located on each side of the oropharynx.
    Submental Lymph Nodes
    Drain the floor of the mouth and central lower lip.
    Tubal Tonsils
    Near openings of the auditory tubes.

    Appendix

    Reviewed by our medical team

    Lymphoid-rich structure of the large intestine.

    1. Overview

    The appendix, or vermiform appendix, is a narrow, finger-like pouch extending from the cecum in the lower right abdomen. Traditionally considered a vestigial organ, recent research has revealed that the appendix plays an active role in the immune system, especially during early life. It is rich in lymphoid tissue and is now recognized as a component of the gut-associated lymphoid tissue (GALT), contributing to mucosal immunity within the gastrointestinal tract.

    2. Location

    The appendix is located in the right lower quadrant of the abdomen, attached to the posteromedial wall of the cecum, about 2–3 cm below the ileocecal valve. Its position can vary, with common orientations including:

    • Retrocecal (most common): Behind the cecum

    • Pelvic: Hanging into the pelvis

    • Subcecal, pre-ileal, or post-ileal: Less common variations

    The blood supply is primarily from the appendicular artery, a branch of the ileocolic artery, which is a branch of the superior mesenteric artery.

    3. Structure

    Histologically, the appendix resembles the rest of the intestinal tract but with key lymphatic adaptations. Its layers include:

    • Mucosa: Lined by simple columnar epithelium with goblet cells; contains crypts but fewer than in the colon

    • Submucosa: Rich in lymphoid follicles, often forming germinal centers—this is the hallmark of its lymphatic role

    • Muscularis externa: Contains inner circular and outer longitudinal muscle layers

    • Serosa: Outermost peritoneal covering

    Unlike most of the colon, the appendix has a particularly dense accumulation of lymphoid tissue, especially in younger individuals.

    4. Function

    The appendix is a lymphoid organ within the gastrointestinal tract that supports both local and systemic immune functions. Its major functions include:

    • Lymphoid defense: Acts as a secondary lymphoid organ, hosting B and T lymphocytes that respond to gut antigens

    • Production of IgA: Promotes mucosal immunity through IgA-producing plasma cells

    • Microbial reservoir: Maintains a reserve of beneficial gut bacteria, which may help recolonize the intestine after infections or antibiotic therapy

    5. Physiological Role(s)

    The appendix has several physiological roles, particularly related to immunological and microbial homeostasis:

    • Early immune development: In children and adolescents, the appendix helps “educate” the immune system through antigen exposure and lymphocyte activation

    • Part of GALT: Acts in coordination with Peyer's patches, mesenteric lymph nodes, and other intestinal lymphoid tissues to regulate immune tolerance and responses to intestinal microbes

    • Maintaining gut flora: The appendix may serve as a safe house for commensal bacteria, aiding in microbial recolonization following diarrhea or illness

    Although its function diminishes with age, its immunological importance is most prominent in early life.

    6. Clinical Significance

    Appendicitis

    Acute appendicitis is the most well-known condition associated with the appendix. It involves inflammation due to obstruction (by fecaliths, lymphoid hyperplasia, or foreign bodies), which can lead to infection, ischemia, and perforation. Clinical features include:

    • Right lower quadrant abdominal pain (McBurney's point)

    • Fever, nausea, and anorexia

    • Elevated white blood cell count

    Untreated appendicitis can lead to peritonitis or abscess formation. Treatment typically involves surgical removal (appendectomy), either laparoscopic or open.

    Lymphoid Hyperplasia

    In children and adolescents, lymphoid hyperplasia in the appendix is a common cause of appendiceal obstruction. It may be triggered by viral infections or systemic immune activation. This is one reason why appendicitis is more frequent in younger populations.

    Appendiceal Tumors

    Although rare, tumors of the appendix include:

    • Carcinoid tumors (neuroendocrine): Most common, usually benign

    • Appendiceal adenocarcinoma

    • Mucinous cystadenoma or cystadenocarcinoma

    These may be discovered incidentally during appendectomy or imaging.

    Role in Surgery and Immunity

    Historically considered expendable, the appendix is now thought to contribute to immune regulation and gut microbial balance. However, removal does not appear to significantly impair systemic immunity. In some cases, the appendix is preserved during surgery unless diseased.

    Diagnostic Imaging

    Imaging studies used in the diagnosis of appendiceal disease include:

    • Ultrasound: Especially useful in children and pregnant women

    • CT scan: Most accurate for detecting appendicitis and complications

    • MRI: Used when radiation exposure is contraindicated

    Did you know? Lymphatic fluid can carry cancer cells from one part of the body to another, which is why cancer often spreads through the lymphatic system.