When using PubMed to search for article citations, you can view the MeSH terms that are tagged to that citation (as long as that citation came from MEDLINE). For MEDLINE-associated citations, the PubMed record has a “MeSH terms” section.
For example, view the record for "The meaning of blood pressure".
You can either scroll down the page or click on the Page Navigation link to jump to "MeSH terms."
Note the different MeSH terms this article is tagged with. There are several heart and health categories, as well as one for "Humans."
Other article citations concerned with blood pressure will be tagged with some or all of these descriptors, such as the article "Minimally invasive monitoring". Several of the same MeSH terms are associated with both articles.