VAN 121: Veterinary Gross Anatomy-II (2+2)

Medulla oblangata

MEDULLA OBLONGATA

• It is the cranial continuation of the spinal cord and extends from the foramen magnum to the posterior margin of the pons. This is a quadrilateral structure wider in front than behind and compressed dorsoventrally.
• Its inferior surface is convex transversely and presents median fissure, which ends in front in a small depression called the foramen caecum and posteriorly it terminates in the central part of a transverse band called the corpus trapezoideum. On either side of medium fissure is a rounded prominence known as inferior pyramids, which pass under the pons in front and disappear gradually behind.
• The corpus trapezoideum is transverse band that lies behind the pons.
• The dorsal surface of medulla oblongata is largely concealed by the cerebellum and forms the greater part of floor of the fourth ventricle. The dorsal median fissure of spinal cord extends to about the middle of the medulla. Here the restiform bodies which constitute the lips of the fissure and diverge to form the lateral boundaries of the posterior part of the fourth ventricle.
• The dorsolateral groove of the spinal cord winds outward and forward to the lateral aspect where it presents the roots of the ninth, tenth and eleventh cranial nerves. The central canal of the spinal cord continues in the posterior part of the medulla and opens into the posterior angle of the fourth ventricle.
• The chorioid plexuses of the fourth ventricle occupy the recess between the medulla oblongata and the cerebellum.
• The medulla oblongata contains ascending and descending fibres and also motor and sensory nuclei of the fifth to the twelfth cranial nerves.