33.2 Blood and the Lymphatic System Lesson Overview 33.2 Blood and the Lymphatic System

BlOOD Plasma Red Blood Cells White Blood Cells Platelets

The Lymphatic System What is the function of the lymphatic system?

The Lymphatic System What is the function of the lymphatic system? The lymphatic system is a network of vessels, nodes, and organs that collects the lymph that leaves capillaries, “screens” it for microorganisms, and returns it to the circulatory system.

The Lymphatic System As blood passes through capillaries, some blood cells and components of plasma move through capillary walls and into the fluid between cells, carrying nutrients, dissolved oxygen, and salts.

The Lymphatic System Most of this fluid, known as lymph, is reabsorbed into capillaries, but not all of it. The rest goes into the lymphatic system, a network of vessels, nodes, and organs that collects the lymph that leaves capillaries, “screens” it for microorganisms, and returns it to the circulatory system. The lymphatic system is also involved in the absorption of nutrients and in immunity.

Role in Immunity Hundreds of small bean-shaped enlargements—called lymph nodes— are scattered along lymph vessels throughout the body. Lymph nodes act as filters, trapping microorganisms, stray cancer cells, and debris as lymph flows through them. White blood cells inside lymph nodes engulf or otherwise destroy this cellular “trash.”