Anatomy of the Medulla Oblongata

Medulla Oblongata Structure

• The medulla oblongata is divided into right and left symmetrical halves by the anterior median fissure and posterior median sulcus.
• The anterior median fissure is continuous with the spinal cord below and ends in a small triangular depression called the foramen caecum above, located at the lower border of the pons.

Decussation of Pyramids

• The anterior median fissure is interrupted in its lower part by the decussation of pyramids, which are bundles of fibers that cross obliquely from one side to the other.

Posterior Median Sulcus

• The posterior median sulcus is present only in the lower half of the medulla oblongata and continues below with the corresponding sulcus of the cord.

Floor of the Fourth Ventricle

• The lips of the posterior median sulcus diverge to form the boundaries of a triangular area, which is the lower part of the floor of the fourth ventricle.

Lateral Sulci

• Each half of the medulla oblongata is marked by two sulci: anterolateral and posterolateral, which are direct upward continuations of the corresponding sulci of the spinal cord.
• The anterolateral sulcus extends along the lateral border of the pyramid and emerges with the rootlets of the hypoglossal (XII cranial) nerve.
• The posterolateral sulcus lies between the olive and the inferior cerebellar peduncle and is where the rootlets of the glossopharyngeal (IX), vagus (X), and accessory (XI) cranial nerves emerge.