phylum. 1  Biology. the primary subdivision of a taxonomic kingdom, grouping together all classes of organisms that have the same body plan. 2  Linguistics. a category consisting of language stocks that, because of cognates in vocabulary, are considered likely to be related by common origin. Compare stock (def 13).
There are between 500 and 600 lymph nodes in the average adult human body.
Lymph nodes are small bean-shaped structures that are usually less than 2.5 cm in length. They are widely distributed throughout the body along the lymphatic pathways where they filter the lymph before it is returned to the blood. Lymph nodes are not present in the central nervous system. There are three superficial regions on each side of the body where lymph nodes tend to cluster. These areas are the inguinal nodes in the groin, the axillary nodes in the armpit, and the cervical nodes in the neck. The typical lymph node is surrounded by a connective tissue capsule and divided into compartments called lymph nodules.