The brainstem lies in the posterior cranial fossa. It faces the clivus of the occipital bone and dorsum sellae of the sphenoid anteriorly, while posteriorly it is connected to the cisterna magna, fourth ventricle, and the cerebellum.

The brainstem is typically 6 - 7.5 centimeters long and 3 - 4 centimeters wide, and it connects the spinal cord, cerebellum and cerebrum to each other.

All parts of the brainstem regulate heart rate, respiration, blood pressure and other essential body functions.

The brainstem contains many cranial nerve nuclei, tracts and neural pathways traveling through. Between those tracts and nuclei, a network of interconnected brainstem nuclei called the reticular formation is located.

The brainstem consists of three parts: