**Histological Structure**

Lymph nodes are encapsulated by a dense connective tissue capsule, which extends inward to form trabeculae,

 dividing the node into compartments⊃1;. The internal structure of a lymph node is divided into three main regions:

1. **Cortex**: The outermost layer, containing lymphoid follicles with germinal centers

 where B lymphocytes proliferate and differentiate. The cortex is further divided into the outer cortex and the paracortex. 

The outer cortex contains B cells, while the paracortex is rich in T cells and dendritic cells⊃2;.

2. **Medulla**: The innermost part of the lymph node, consisting of medullary cords and sinuses. 

The medullary cords contain plasma cells, macrophages, and B cells, while the medullary

 sinuses are channels that allow lymph to flow through the node⊃2;.

3. **Sinuses**: These are spaces within the lymph node that facilitate the movement of lymph.

 They include the subcapsular sinus, cortical sinuses, and medullary sinuses⊃1;.

**Function**

Lymph nodes have several critical functions:

1. **Filtration of Lymph**: Lymph nodes filter lymph fluid, trapping bacteria, viruses, 

and other foreign particles. Macrophages within the nodes phagocytose these particles, preventing them from entering the bloodstream⊃3;.

2. **Immune Response Activation**: Lymph nodes are sites where immune responses are initiated. Antigens are presented to lymphocytes within the nodes,

 leading to the activation and proliferation of B and T cells. This process is crucial for the body's adaptive immune response⁴.

3. **Production of Immune Cells**: Lymph nodes produce and release lymphocytes into the lymphatic system,

 contributing to the body's overall immune surveillance⁴.