Most of us have felt the glands in our necks enlarge and grow tender when we have the flu, or those under the arm or near the elbow swell when a finger becomes infected. These glands are actually lymph nodes.
Usually one or more of these nodes lie in the pathway of the lymphatic vessels and filter the lymph on its way to the bloodstream. In each node, a labyrinth of channels weaves through a dense webbing of tissue divided into compartments. Each compartment houses a distinct population of while blood cells. As the incoming lymph trickles through the channels of he node, some particles get caught in the webbing or fall prey to white blood cells.
In this way, the nodes filter out foreign chemicals, particles and micro-organisms before they enter the bloodstream. This function was discovered during an autopsy performed on a heavily tattooed sailor. His lymph nodes showed traces of ink.
When an un-welcomed organism arrives at a node from a site of infection, the innate intelligence of the body commands the brain to send chemo-electrical-mental impulses down the spinal cord, in through the nerves to stimulate the node which swells as the white blood cells within divide and multiply in response to the invader.
Amazing isn’t it?