10. LYMPHATIC SYSTEM

Lymphatic System

Introduction

The lymphatic system is an essential part of the circulatory and immune systems. It helps maintain the body’s fluid balance, absorbs fats from the digestive tract, and protects the body against infections.
It acts as a drainage system, collecting excess fluid from tissues and returning it to the bloodstream while also filtering harmful substances.

Original Notes:

Definition

The lymphatic system is a network of lymphatic vessels, lymph nodes, and lymphoid organs that transport lymph — a clear fluid containing white blood cells — throughout the body.

Main Components of the Lymphatic System

1. Lymph
   • A clear, colorless fluid similar to plasma but with fewer proteins.
   • It contains lymphocytes (mainly T-cells and B-cells), which fight infections.
   • Lymph also carries nutrients, hormones, and waste products.
2. Lymph Capillaries and Vessels
   • Tiny, closed-ended tubes found in most body tissues.
   • They collect tissue fluid and merge to form larger lymph vessels.
   • These vessels have valves that ensure one-way flow of lymph towards the heart.
3. Lymph Nodes
   • Small bean-shaped structures found along lymph vessels.
   • Act as filters, trapping bacteria, dead cells, and foreign particles.
   • Contain lymphocytes and macrophages that destroy pathogens.
   • Commonly located in the neck, armpits, groin, and abdomen.
4. Lymphoid Organs
   The main lymphoid organs are:
   • Thymus: Located in the upper chest; responsible for the maturation of T-lymphocytes.
   • Spleen: Largest lymphatic organ; filters blood, removes old RBCs, and stores lymphocytes.
   • Tonsils: Present in the throat region; act as the first line of defense against infections entering through the mouth or nose.
   • Bone Marrow: Produces lymphocytes and other blood cells.
   • Peyer’s Patches: Found in the small intestine; protect the body from ingested pathogens.
5. Thoracic Duct and Right Lymphatic Duct
   • The thoracic duct drains lymph from most of the body into the left subclavian vein.
   • The right lymphatic duct drains lymph from the right side of the head, chest, and arm into the right subclavian vein.
   • Both return lymph to the bloodstream, maintaining fluid balance.

Functions of the Lymphatic System

• Drainage of Tissue Fluid: Returns excess tissue fluid to the bloodstream, preventing swelling (edema).
• Transport of Fats: Absorbs fats and fat-soluble vitamins (A, D, E, K) from the small intestine through lymphatic capillaries called lacteals.
• Immune Defense: Produces and transports lymphocytes that fight infections and destroy harmful microorganisms.
• Filtration of Lymph: Lymph nodes filter out bacteria and foreign particles before returning lymph to circulation.
• Maintenance of Fluid Balance: Regulates the amount of fluid in tissues and blood volume.

Disorders of the Lymphatic System

1. Lymphedema: Swelling due to blockage in lymph vessels or removal of lymph nodes.
2. Lymphadenitis: Inflammation of lymph nodes caused by infection.
3. Lymphoma: Cancer of the lymphatic system (e.g., Hodgkin’s and Non-Hodgkin’s lymphoma).
4. Elephantiasis: Caused by filarial worms blocking lymph vessels, leading to severe swelling.