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.
There are more than 500 of them throughout the body, but theyâre most noticeable in the head and neck and under the arms, where theyâre closer to the surface of the skin. A healthy lymph node is about one centimeter wide, but exposure to germs or infection can cause it to swell to as much as an inch in diameter.