LYMPHATIC SYSTEM : A BRIEF OVERVIEW

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LYMPHATIC SYSTEM

 

OVERVIEW: - The lymphatic System of the human body refers to the system by which lymph—a clear fluid containing white blood cells—is collected from tissues and returned to the bloodstream. It plays a critical role in immune defence and fluid balance.

 

Main Components of the Lymphatic System

  1.  Lymph
    • A clear fluid that circulates in lymphatic vessels
    • Contains white blood cells (mainly lymphocytes), proteins, and fats
    • Formed from interstitial fluid that leaks out of capillaries
  2.  Lymphatic Vessels
    • Network of thin tubes that carry lymph
    • Begin as lymphatic capillaries, which merge into larger vessels
    • Have valves to prevent backflow
    • Ultimately drain into the thoracic duct or right lymphatic duct
  3.  Lymph Nodes
    • Small, bean-shaped structures located along lymphatic vessels
    • Filter lymph to remove pathogens and debris
    • Contain lymphocytes and macrophages
    • Found in clusters (e.g., cervical, axillary, inguinal)
  4. Lymphoid Organs
    • Primary lymphoid organs:
      • Bone marrow – site of blood cell production, including lymphocytes
      • Thymus – T lymphocyte maturation
    • Secondary lymphoid organs:
      • Spleen – filters blood, destroys old RBCs, mounts immune response
      • Lymph nodes – monitor lymph
      • Tonsils – protect against pathogens entering through the mouth/nose
      • Peyer’s patches – in small intestine, monitor gut pathogens
  5. Lymphocytes
    • B cells – mature in bone marrow; produce antibodies
    • T cells – mature in thymus; destroy infected or cancerous cells
    • Essential for adaptive immunity
  6. Cisterna Chyli
    • A dilated sac at the lower end of the thoracic duct
    • Receives lymph from abdominal and lower limb regions


    Main Lymphatic Vessels

  1. Thoracic Duct

    • Drains lymph from:

      • Left side of head and neck

      • Left upper limb

      • Left thorax

      • Entire abdomen

      • Both lower limbs

    • Empties into: Left subclavian vein

  2. Right Lymphatic Duct

    • Drains lymph from:

      • Right side of head and neck

      • Right upper limb

      • Right thorax

    • Empties into: Right subclavian vein



    Regional Lymphatic Drainage:


1.Lymph Node Levels of the Head and Neck

🔹 Level I: Submental and Submandibular Nodes

  • Level Ia (Submental):


    • Location: Between the anterior bellies of the digastric muscles and the hyoid bone.


    • Drains: Chin, lower lip, floor of the mouth, and tip of the tongue.

  • Level Ib (Submandibular):

    • Location: Between the anterior and posterior bellies of the digastric muscle and the mandible.

    • Drains: Cheeks, upper lip, anterior nasal cavity, lateral tongue, and submandibular gland.​

🔹 Level II: Upper Jugular Nodes

  • Location: From the skull base to the hyoid bone, anterior to the sternocleidomastoid muscle.

  • Subdivisions:

    • Level IIa: Anterior to the spinal accessory nerve.

    • Level IIb: Posterior to the spinal accessory nerve.

  • Drains: Oral cavity, pharynx, larynx, parotid gland, and upper cervical esophagus.​

🔹 Level III: Middle Jugular Nodes

  • Location: From the hyoid bone to the cricoid cartilage, along the internal jugular vein.

  • Drains: Oral cavity, larynx, hypopharynx, and thyroid gland.​

🔹 Level IV: Lower Jugular Nodes

  • Location: From the cricoid cartilage to the clavicle, along the internal jugular vein.

  • Drains: Hypopharynx, larynx, thyroid gland, and cervical esophagus.​

🔹 Level V: Posterior Triangle Nodes

  • Location: Posterior to the sternocleidomastoid muscle, extending to the trapezius muscle.

  • Subdivisions:

    • Level Va: Above the cricoid cartilage.

    • Level Vb: Below the cricoid cartilage to the clavicle.

  • Drains: Scalp, nasopharynx, and thyroid gland.​

🔹 Level VI: Anterior (Central) Compartment Nodes

  • Location: Between the carotid arteries, from the hyoid bone to the suprasternal notch.

  • Drains: Thyroid gland, glottis, subglottic larynx, trachea, and cervical esophagus.​

🔹 Level VII: Superior Mediastinal Nodes

  • Location: Below the suprasternal notch in the upper mediastinum.

  • Drains: Thyroid gland, trachea, and upper esophagus.





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