Editing Brain tumor (section)

===Brain matter===
The three largest divisions of the brain are the [[Cerebrum|cerebral cortex]], [[cerebellum]] and the [[brainstem]].<ref name=":7" /> These areas are composed of two broad classes of cells: [[neurons]] and [[glia]]. These two cell types are equally numerous in the brain as a whole, although [[glial cells]] outnumber [[neurons]] roughly 4 to 1 in the [[cerebral cortex]]. Glia come in several types, which perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development.<ref>{{Cite web|url=https://training.seer.cancer.gov/brain/tumors/anatomy/neurons.html|title=Neurons & Glial Cells SEER Training|website=training.seer.cancer.gov|access-date=29 July 2019}}</ref> Primary tumors of the glial cells are called [[glioma]]s and often are malignant by the time they are diagnosed.<ref>{{cite journal | vauthors = Ostrom QT, Gittleman H, Farah P, Ondracek A, Chen Y, Wolinsky Y, Stroup NE, Kruchko C, Barnholtz-Sloan JS | title = CBTRUS statistical report: Primary brain and central nervous system tumors diagnosed in the United States in 2006-2010 | journal = Neuro-Oncology | volume = 15 | issue = Suppl 2 | pages = ii1-56 | date = November 2013 | pmid = 24137015 | pmc = 3798196 | doi = 10.1093/neuonc/not151 }}</ref>

The [[thalamus]] and [[hypothalamus]] are major divisions of the [[diencephalon]], with the [[pituitary gland]] and [[pineal gland]] attached at the bottom; tumors of the [[pituitary]]<ref>{{Cite web |title=Pituitary tumours |url=https://www.cancerresearchuk.org/about-cancer/brain-tumours/types/pituitary-tumours |archive-url=https://web.archive.org/web/20240301203755/https://www.cancerresearchuk.org/about-cancer/brain-tumours/types/pituitary-tumours |archive-date=1 March 2024 |access-date=18 April 2024 |website=www.cancerresearchuk.org |language=en}}</ref> and [[pineal gland]]<ref>{{Cite web |last=Kashani |first=Shayan |title=What to Know About Pineal Tumors |url=https://www.webmd.com/brain/what-to-know-about-pineal-tumors |access-date=2024-07-04 |website=WebMD |language=en}}</ref> are often benign.

The [[brainstem]] lies between the large cerebral cortex and the spinal cord. It is divided into the midbrain, pons, and medulla oblongata.<ref name=":7" />