Lymphatic System: Study Notes

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Lymphatic System

• Network of lymph vessels that collect lymph and return it to the circulatory system.
• Includes lymph nodes, thymus, and spleen, key to immune functions.

Interstitial Fluid Formation

• Surrounds body tissues, formed when blood passes through capillaries.
• Capillary walls allow passage of water and solutes, but not RBCs or large proteins.

Interstitial Fluid vs. Lymph

• 85% of interstitial fluid returns to blood; 15% enters lymphatic capillaries as lymph.
• Lymph contains WBCs, lymphocytes, proteins, fats, and cellular debris.

Lymphatic Vessels

• Thin-walled vessels with openings for fluid and large particles.
• Lymph flow aided by muscle contractions and regulated by one-way valves.

Role in Villi

• Lymph capillaries (lacteals) in the small intestine absorb digested fats.
• Fat globules, too large for blood capillaries, enter lymphatic capillaries.

Lymph Nodes and Spleen

• Lymph nodes filter lymph; macrophages and lymphocytes destroy pathogens.
• Spleen filters blood, removing old RBCs and exposing it to immune cells.

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