Structure Of Lymph Nodes and Lymphatics

This section based on Gray's Anatomy (40th edition) and Moore's Clinical Anatomy (7th edition)

Lymphatics

Lymph Nodes

Macroscopic Features

A lymph node is classically described as an encapsulated kidney-shaped structure, with numerous afferent vessels piercing its surface. The hilum of the lymph node contains the efferent lymphatic vessel as well as arterial and venous supply. Valves prevent retrograde passage of lymph from the efferent vessel into the node and from the node along the afferent vessels. Lymph nodes are typically 0.1 - 2.5 cm in size.
On the cut surface, the lymph node consists of the external capsule, which sends fibrous trabeculae centrally towards the hilum. Just beneath the capsule is the subcapsular sinus, which contains lymph from the afferent vessels. The remaining substance of the node is layered into the cortex, paracortex, and medulla from outside in. Lymph passes through these three layers to reach the medullary sinus, which then continues outside the node as the efferent vessel.
The primary lymphoid follicles are located in the cortex of the lymph node.

Microscopic Features

The fibrous trabeculae give rise to a fine reticular network of collagen fibres which provide the microscopic support of the node. Small lymphatic sinuses pass through the cortex and medulla to reach the medullary sinus. The cells