MeSH is the acronym for Medical Subject Headings. MEDLINE uses a controlled vocabulary, meaning that there is a specific set of terms used to describe each article. Each MeSH term represents a single concept used in the biomedical literature. Familiarity with this vocabulary will make you a better PubMed searcher, as the best way to search PubMed is to use MeSH terms. MeSH imposes uniformity and consistency to the indexing of biomedical literature. MeSH terms are arranged in a hierarchical categorized manner called MeSH Tree Structures.
You will see that the MeSH "trees" are represented by a picture of trees on the homepage of the database. The MeSH Tree is composed of many different biomedical concepts, as well as many non-clinical topics.
The MeSH vocabulary is organized by 16 main branches, including those listed below:
The branches of the MeSH Tree represent many different types of relationships. Each branch represents a set of complex hierarchical terms which become increasingly specific (or narrow) as the hierarchy develops relationships between terms. Headings are positioned in the tree according to their relationship to other headings.
The MeSH controlled vocabulary consists of four different types of terms:
When you search in Google you generally do not make use of the fairly sophisticated search syntax that is available to you. Most often you will use a simple keyword (or several keywords), in other words you search using "natural" language as you would use in everyday speech. So if for example you want to find information on high blood pressure, you can simply type this "string" of words into the Google search bar, and you will get a great deal of information on the topic.
However, much of this information may not be relevant, especially when you are searching for clinical information on how to deal with this condition. For example, a search for high blood pressure in Google resulted in over 100 million hits. Most of these hits were articles designed for the lay public, and not for health professionals.
So although the information you find using Google might be useful, it will not help you to focus your search for the clinical information that you will use in your health science studies, or for your clinical practice.
As the volume and complexity of medical knowledge grows, so too does the language used to describe this knowledge. Finding the right term or keyword to describe a medical condition or problem can be daunting. The Medical Subject Headings database (or MeSH for short) is designed to help you focus your search, and to avoid ambiguous terms or synonyms, ie. where one words can mean many different things, or where different words are used for the same topic.
Using MeSH therefore makes your search
You can find the MeSH database at http://www.ncbi.nlm.nih.gov/mesh
Each MeSH term represents a single concept used in the biomedical literature. MeSH headings may be broad in scope, eg. Anatomy, or narrow in scope, eg. Eyelashes.
The most general terms are at the top of the tree (hierarchy), eg. Medical Informatics, and the three main sub-branches of this topic; Public Health Informatics, Medical Informatics Computing, and Medical Informatics Applications. The most specific (narrowest) terms are found at the bottom of the tree (hierarchy).