Medulla oblongata


The medulla is the lowest part of the brain stem and the brain itself. It is divided into two main parts


 Medulla which is also called the open medulla.


Lower medulla also called the closed medulla.

 The open medulla is so called because it opens into the fourth ventricle. The 4th ventricle is placed at its back. The closed medulla is so called because it is closed with a central canal within its substance just as you have in the spinal cord.

  The closed medulla is closed because it has the central canal of the medulla buried in its middle. 

The medulla has at its ventral surface, the pyramids on the two sides of the anteriomedian sulcus. Lateral to the pyramids are the olivo-pyramidal interval which form  sulci for the escape of rootlets of the hypoglossal nerve. Lateral to the olive is the  postolivary sulcus and it carries the rootlets of cranial nerves 9, 10 and 11- glossopharyngeal, vagus and accessory nerves.

Posterior aspect of the medulla has the tuberculum gracilis most lateral to the posteromedian fissure and lateral to it is the tuberculum cuneatus. The two tubercula have buried in them the nuclei gracilis and cuneatus respectively. At the back of the upper medulla is the 4th ventricle. It is covered at the back of the medulla by the inferior medullary velum and tela choroidea. The floor of the 4th ventricle is called the rhomboid fossa.

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Dorsal brainstem (rhomboid fossa)

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