MeSH, or Medical Subject Headings, is the most reputable controlled vocabulary in the biomedical community. First introduced in 1963 by the U.S. National Library of Medicine (NLM), it consists today of 26,853 descriptors. Its use enables health information seekers to search and retrieve scientific articles from among the more than 20 million that are indexed in the NLM databases MEDLINE and PubMed [1].
Most descriptors are accompanied by a definition and are organized in a hierarchical tree that permits searching at various levels of specificity [1]. Medical specialties, study designs, diseases, anatomical body parts, and many chemical and pharmaceutical components share the privilege of existing as MeSH descriptors. The most intimate parts of the body—penis, vagina, vulva, foreskin, anal canal, Bartholin's glands, breasts—are well located, organized, enumerated, and defined in the MeSH repository. “Labia minora” and “labia majora,” however, do not yet appear in MeSH. “Clitoris” does exist as a descriptor, though still undefined. Its tree number is A05.360.319.887.436: “All MeSH Categories” > “Anatomy category” > “Urogenital System” > “Genitalia” > “Genitalia, Female” > “Vulva” > “Clitoris”. It can also be linked to 23 other subheadings [1].