Which of the following statements accurately defines lymph node?
A. A group of cells that plays various roles in the immune system
B. Small cellular fragments involved in blood clotting
C. Encapsulated lymphoid organs found along the lymphatic vessels that filter lymph and remove pathogens, toxins, and cells
D. Granulocyte whose granules interact strongly with the red dye eosin; less numerous than neutrophils
The correct answer and explanation is:
The correct answer is C: Encapsulated lymphoid organs found along the lymphatic vessels that filter lymph and remove pathogens, toxins, and cells.
Lymph nodes are small, bean-shaped organs located throughout the body along the lymphatic system. They play a crucial role in immune defense by filtering lymph, which is a fluid that circulates through the lymphatic system. Lymph nodes are encapsulated, meaning they are surrounded by a protective layer of connective tissue. Within these nodes, there are specialized areas where immune cells, such as lymphocytes (B-cells and T-cells), are located.
The primary function of lymph nodes is to filter lymph and trap harmful substances like pathogens (e.g., bacteria, viruses), toxins, and foreign particles. They do so through a combination of physical filtration and immune response. The lymph fluid enters the lymph node through afferent lymphatic vessels, passes through the node, and exits via the efferent lymphatic vessels. During this process, immune cells identify and mount an immune response against any pathogens or abnormal cells present.
In addition to their filtering role, lymph nodes also play an important part in the activation of adaptive immunity. When a pathogen is detected, immune cells in the lymph node, particularly dendritic cells, activate T-cells. These activated T-cells then circulate to other parts of the body, targeting and destroying infected cells. B-cells in the lymph nodes also produce antibodies to neutralize pathogens.
Lymph nodes are distributed throughout the body in areas like the neck, armpits, groin, and abdomen, and their size can increase when an infection is present. This is commonly observed as swollen lymph nodes, a sign of immune system activation.