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M01.03.040 Lymphatics
The lymphatic system plays a crucial role in maintaining fluid balance by draining tissue fluid, plasma proteins, and other cellular debris back into the bloodstream. It also functions as an essential part of immune defense. This article explores the anatomy of lymphatic drainage in the upper limb, including lymphatic vessels, lymph nodes, and clinical correlations.
Key Functions of the Lymphatic System
- Drains tissue fluid and proteins back into the bloodstream.
- Filters cellular debris from the extracellular space.
- Contributes to immune defense by transporting immune cells to sites of infection.
Anatomy of Lymphatic Drainage in the Upper Limb
1. Lymphatic Vessels
The lymphatic vessels are classified into superficial and deep vessels, each with distinct pathways and functions.
Superficial Lymphatic Vessels
- Origin: Begin in the skin of the hand as lymphatic plexuses (networks of capillaries).
- Pathway: Travel along the major superficial veins of the arm.
| Superficial Lymphatic Vessels | Pathway |
|---|---|
| Basilic Vein | Enters cubital lymph nodes, then lateral axillary nodes |
| Cephalic Vein | Crosses the arm to enter apical axillary nodes or deltopectoral lymph nodes |
Deep Lymphatic Vessels
- Origin: Follow the major deep veins of the arm (radial, ulnar, and brachial veins).
- Function: Drain lymph from joint capsules, periosteum, tendons, and muscles.
| Deep Lymphatic Vessels | Pathway |
|---|---|
| Radial/Ulnar/Brachial Veins | Drain into humeral axillary lymph nodes |
2. Lymph Nodes
The upper extremity lymph nodes are predominantly located in the axilla and are divided into five groups.
Axillary Lymph Node Groups
| Group | Location | Lymph Drainage |
|---|---|---|
| Pectoral | Medial wall of the axilla | Anterior thoracic wall, including the breast |
| Subscapular | Posterior axillary fold and subscapular blood vessels | Posterior thoracic wall, scapular region |
| Humeral | Lateral wall of the axilla, posterior to the axillary vein | Upper limb |
| Central | Near the base of the axilla, deep to pectoralis minor | Pectoral, subscapular, and humeral groups |
| Apical | The apex of the axilla, near axillary vein and artery | All axillary groups, plus lymph from the cephalic vein |
Lymphatic Flow
- Efferent vessels from the apical axillary nodes converge to form the subclavian lymphatic trunk.
- Right subclavian trunk: Forms the right lymphatic duct, draining into the right venous angle.
- Left subclavian trunk: Drains into the thoracic duct.
Clinical Relevance
1. Axillary Lymphadenopathy
- Definition: Enlargement of axillary lymph nodes.
- Causes:
- Infection: Lymphangitis, with tender, enlarged lymph nodes.
- Breast Cancer Metastasis: Lymph nodes may be enlarged due to metastatic spread.
- Affected Group: The humeral group is usually the first to be affected.
2. Axillary Lymph Node Dissection
- Purpose: Removal of lymph nodes for breast cancer staging.
- Risks:
- Lymphedema: Accumulation of lymph causing painful swelling.
- Nerve Injury: Damage to the long thoracic nerve (winged scapula) or thoracodorsal nerve.
Points to Remember
- Superficial vessels follow the major veins and drain into the axillary nodes.
- Deep vessels drain from joints and muscles into the humeral axillary nodes.
- Lymphatic flow from the axillary nodes is vital for maintaining fluid balance and immune function.
- Axillary lymphadenopathy can be a sign of infection or cancer.
- Lymph node dissection is a key part of cancer staging but may result in complications like lymphedema.