Anatomy & Physiology

Lesson 15 of 20

Lymphatic & immune systems

The lymphatic system returns excess interstitial fluid to the circulation, absorbs certain dietary fats, and provides routes for immune surveillance. Lymph nodes filter lymph and contain immune cells. The immune system distinguishes and responds to threats through coordinated innate and adaptive defenses. Lymphatic and immune functions overlap but are not identical.

Key points

• Lymph begins as interstitial fluid collected into lymphatic vessels.
• Lymph nodes filter lymph and provide sites for immune-cell activity.
• The spleen filters blood and supports immune functions; it is not a lymph node.
• Innate defenses respond broadly; adaptive defenses include targeted B-cell and T-cell responses.
• Lymphatic vessels ultimately return lymph to venous circulation.

Key terms

Lymph

Fluid collected from interstitial spaces and transported in lymphatic vessels.

Lymph node

Small immune organ that filters lymph and supports immune-cell responses.

Spleen

Organ that filters blood and contributes to immune function.

Innate immunity

Rapid, broad defense mechanisms present without prior specific exposure.

Adaptive immunity

Specific immune response involving lymphocytes and immunological memory.