Anatomy of Lymph Nodes
Introduction
The lymphatic system includes:
- Lymphatic vessels
- Lymphoid organs: thymus, tonsils, lymph nodes, spleen
- Functions in immunity, fluid filtration/drainage, and cell recycling
- Lymphatic drainage: via right lymphatic duct and thoracic duct into subclavian arteries
Structure and Function
- Kidney-shaped lymph nodes filter lymph via afferent and efferent vessels
- Associated with artery and vein, terminating in high endothelial venule (HEV)
Lymph Node Structure
Capsule
- Dense connective tissue with collagen fibers and trabeculae
Subscapular Sinus
- Space between capsule and cortex; facilitates lymph transport
Cortex
- Outer cortex (B-cell layer) with germinal centers
- Paracortex (T-cell layer) enriched with CCR7 chemokines
Medulla
- Contains medullary cords with plasma cells, B-cells, macrophages
Function
- Filters interstitial fluid, exposing T/B-cells to antigens
- Involves antigen-presenting cells and dendritic cells in immune response
Embryology
- Begins as mesenchymal condensation
- T-cell region develops by 13th gestational week
- B-cell regions develop by 14th gestational week
Blood Supply and Lymphatics
Head and Neck
- Superficial Nodes: Occipital, Mastoid, Pre-auricular, Parotid, etc.
- Deep Nodes: Deep parotid and deep cervical
Anatomical Levels of the Neck
- Levels I-VI defining positions and drainage areas
Upper Limb
- Axillary Nodes: Anterior, Posterior, Lateral, Central, and Apical
- Supratrochlear and cubital nodes at the elbow
Lower Limb
- Inguinal Nodes: Superficial and deep sub-inguinal nodes
- Iliac Nodes: External and common iliac nodes
Clinical Significance
- Lymph node enlargement may indicate infection, inflammation, or malignancy
- Diagnosis with endoscopic ultrasound (EUS) and fine-needle aspiration
- Imaging techniques like PET scans used for staging malignancy
This summary provides an overview of lymph node anatomy, structure, function, embryology, and clinical significance, essential for understanding their role in the lymphatic and immune systems.