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The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. [1] In the human brain the brainstem is composed of the midbrain , the pons , and the medulla oblongata . [ 1 ]
The pontine tegmentum, or dorsal pons, is the dorsal part of the pons located within the brainstem. The ventral part or ventral pons is known as the basilar part of the pons, or basilar pons. Along with the dorsal surface of the medulla oblongata, it forms part of the rhomboid fossa – the floor of the fourth ventricle.
The pons is also called the pons Varolii ("bridge of Varolius"), after the Italian anatomist and surgeon Costanzo Varolio (1543–75). [1] This region of the brainstem includes neural pathways and tracts that conduct signals from the brain down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus. [2]
The tegmentum (from Latin for "covering") is a general area within the brainstem. The tegmentum is the ventral part of the midbrain and the tectum is the dorsal part of the midbrain. [1] It is located between the ventricular system and distinctive basal or ventral structures at each level.
Brainstem (dorsal view) A:Thalamus B:Midbrain C:Pons D:Medulla oblongata 7 and 8 are the four colliculi. The midbrain is the shortest segment of the brainstem, measuring less than 2cm in length. It is situated mostly in the posterior cranial fossa, with its superior part extending above the tentorial notch. [2]
Fibers of the posterior column, which transmit sensory and proprioceptive information, are located behind the pyramids on the medulla oblongata. The medullary pyramids contain motor fibers that are known as the corticobulbar and corticospinal tracts. The corticospinal tracts are on the anterior surface of the pyramids.
Each olivary body is located on the anterior surface of the medulla lateral to the pyramid, from which it is separated by the antero-lateral sulcus and the fibers of the hypoglossal nerve. Behind ( dorsally ), it is separated from the postero-lateral sulcus by the ventral spinocerebellar fasciculus .
The brainstem includes the midbrain, the pons, and the medulla oblongata. Behind the brainstem is the cerebellum (Latin: little brain). [7] The cerebrum, brainstem, cerebellum, and spinal cord are covered by three membranes called meninges. The membranes are the tough dura mater; the middle arachnoid mater and the more delicate inner pia mater.