Medulla Oblongata Anatomy Quiz

Brain Stem

• Located at the base of the brain, between the deep structures of the cerebral hemispheres and the cervical spinal cord
• Approximately 3 inches in length in an adult person
• Divided into three regions: midbrain, pons, and medulla oblongata

Midbrain

• Superior (rostral) region of the brainstem
• Divided into anterior (anterolateral) and posterior parts by the cerebral aqueduct
• Posterior part: tectum
• Anterior part: two cerebral peduncles, comprising the tegmentum and crura cerebri
• Substantia nigra lies between the cerebral peduncles, plays a role in motor planning and eye movement coordination
• Nuclei of cranial nerves III and IV located here

Pons

• Middle and largest part of the brainstem
• Lies between the midbrain and medulla oblongata, ventral to the cerebellum
• Connected to the cerebellum via the middle cerebellar peduncle
• Nuclei of cranial nerves V-VIII located here
• Ventral part characterized by the bulge of transverse pontocerebellar fibres, with the basilar artery located in the midline

Medulla Oblongata

• Lowest and smallest part of the brainstem
• Continues down as the spinal cord
• Point of junction with the spinal cord (cervico-medullary junction) marked by the foramen magnum of the skull externally and the obex of the floor of the fourth ventricle internally
• External surfaces: anterior, posterior, and lateral
• Anterior surface: anterior median fissure, ventrolateral sulcus, posterolateral sulcus, and pyramids
• Posterior surface: forms the lower part of the floor of the fourth ventricle, with the posterior median fissure, gracile fasciculus, and cuneate fasciculus

Clinical Significance

• Even small lesions of the brainstem may have profound effects
• Brainstem disorders can result in speech disorders, vestibular disturbance, abnormal consciousness, dysphagia, and respiratory disturbance
• Complete loss of brainstem function is regarded by some experts as equivalent to brain death