The correct answer is: All of the above.
Here's why:
1. **Filter lymph:** Lymph nodes function as filters for lymph, which is a clear fluid that circulates through the lymphatic system. As lymph flows through the nodes, they help to remove and trap foreign particles, debris, and abnormal cells present in the lymph.
2. **Phagocytize foreign substances:** Within the lymph nodes, specialized immune cells called macrophages are present. These cells have the ability to engulf and digest foreign substances, such as bacteria, viruses, and other pathogens, helping to eliminate potential threats to the body.
3. **Produce lymphocytes:** Lymph nodes are key sites for the production and maturation of lymphocytes, a type of white blood cell crucial for the body's immune response. B cells and T cells, two main types of lymphocytes, are generated and activated in the lymph nodes, where they play essential roles in recognizing and fighting off infections and other invaders.
By performing these functions, lymph nodes contribute significantly to the body's immune defense system, aiding in the recognition, neutralization, and removal of harmful agents to maintain overall health and well-being.
