LYMPH NODES

Location: wide distribution throughout the body, concentration in axilla, groin, and mesenteries. They are interposed in the pathway of lymphatic vessels.

Function: filtration of the lymph, phagocytosis of particulate material, presentation of antigens to immunocompetent B cells.

Anatomic features

• Afferent lymphatic vessels convey lymph toward the node and enter at variant points on the convex surface of the capsule.
• Efferent lymphatic vessels convey lymph away from the node and leave at the hilum that also serves for the entry and exit of blood vessels and nerves.

SUPPORTING ELEMENTS

• Capsule - dense connective tissue that surrounds the node
• Trabeculae - dense connective tissue that extend from the capsule into the substance of the node, forming a gross framework
• Reticular tissue - forms a fine meshwork.

CORTEX

Location: the outer portion of the node.

Composition:

• Dense mass of lymphatic tissue in the form of primary and secondary nodules with B lymphocytes, macrophages and plasma cells
• Deep cortex (juxtamedullary cortex, paracortical zone, thymus-dependent cortex) with T lymphocytes
• Supporting elements
• Lymphatic sinuses

MEDULLA

Location: the inner part of the node.

Composition:

• Cordes of lymphatic tissue with B lymphocytes, macrophages, and plasma cells
• Supporting elements
• Lymphatic sinuses

SINUSES

Function: lymph channels, monitoring the lymph as it percolates the sinus.

Location:

• Cortical (subcapsular) sinus - between the capsule and cortical lymphocytes into which the afferent lymphatic vessels drain lymph.
• Trabecular (peritrabecular) sinuses - extend through the cortex with trabeculae
• Medullary sinuses - converge toward the hilum, were they drain into efferent lymphatic vessels

Composition: the discontinious endothelium. The lumen is span with macrophage processes and reticular fibers surrounded by reticular cell processes.