Lymph nodes: Lymph nodes are small encapsulated organs located along the pathway of lymphatic vessels. They vary from about 1 mm to 1 to 2 cm in diameter and are widely distributed throughout the body, with large concentrations occurring in the areas of convergence of lymph vessels. They serve as filters through which lymph percolates on its way to the blood. Antigen-activated lymphocytes differentiate and proliferate by cloning in the lymph nodes. They are packed tightly with the white blood cells called lymphocytes and macrophages.
The lymph nodes filter and monitor the lymph, an interstitial fluid, for foreign particles. These foreign particles commonly known as pathogens, or germs, can set up infections anywhere in the body. The lymph fluid inside of the lymph nodes contains lymphocytes, a type of white blood cell, which are continuously recirculated through the lymph nodes and the bloodstream. A germ, such as bacteria, will produce a chemical substance called an antigen which circulates through the bloodstream, the lymph system, and into lymph nodes. In response to the antigens, the lymphocytes in the lymph node make an antibody which will go out of the lymph node into circulation, seek, and destroy the infection producing the antigen. Other immune system cells will be made to fight the infection and "sent" to the lymph nodes. The increased numbers of immune system cells fighting the infection will make the node expand and become "swollen."
Germinal Center- source of lymphocytes
Efferent lymph veins
Medullary region – source of macrophages
1. Cervical Lymph Nodes
Cervical lymph nodes are lymph...