The myelencephalon is a developmental categorization of a portion of the central nervous system. The myelencephalon is composed of the medulla; contains a portion of the fourth ventricle; as well as the glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), hypoglossal nerve (CN XII), and a portion of the vestibulocochlear nerve (CN VIII). Morphogenesis (from the Greek morphê shape and genesis creation) is one of three fundamental aspects of developmental biology along with the control of cell growth and cellular differentiation. ... The vertebrate central nervous system consists of the brain and spinal cord. ... Medulla can refer to: The medulla oblongata, a part of the brainstem Medulla, Florida, a U.S. city The 2004 music album Medúlla by Icelandic singer Björk. ... The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. ... The glossopharyngeal nerve is the ninth of twelve cranial nerves. ... The vagus nerve is tenth of twelve cranial nerves and the only nerve that starts in the brainstem (somewhere in the medulla oblongata) and extends way down past the head, all the way down to the abdomen. ... The accessory nerve is the eleventh of twelve cranial nerves. ... The hypoglossal nerve is the twelfth cranial nerve. ... The vestibulocochlear nerve is the eighth of twelve cranial nerves, and also known as the auditory nerve. ...