Medulla Oblongata Structure and Function

Medulla Oblongata (Bulbus/Medulla)

• The medulla oblongata is the most inferior part of the brainstem.
• It resembles the widening of the spinal cord upward.

Surfaces of Medulla Oblongata

• Anterior surface: The anterior surface shows features like the anterior perforated substance, cranial nerves (e.g., oculomotor, trochlear, etc.), and the pyramidal decussation.
• Posterolateral surface: This region shows the inferior cerebellar peduncles and various cranial nerve nuclei (e.g., glossopharyngeal, vagus).

Anterior Surface: External Features

• Features from midline laterally: Structures like the anterior median fissure, pyramids, pyramidal decussation, and the anterolateral sulcus are visible, with exits for specific cranial nerves (e.g., hypoglossal, glossopharyngeal, vagus, accessory).
• Cranial nerves exiting: specific nerves, such as the glossopharyngeal, vagus, and accessory, emerge from this surface.

Posterior Surface of Medulla Oblongata

• Key structures of posterolateral surface: The posterior surface displays structures like the inferior cerebellar peduncles, the cuneate and gracilis nuclei, and cranial nerve nuclei.

Inferior Cerebellar Peduncle

• Connects the medulla to the cerebellum.
• Contains tracts like the posterior spinocerebellar tract, fibers from the anterior and cuneocerebellar tracts.
• Other pathways involving olivocerebellar and vestibulocerebellar tracts.
• Includes cerebellar fibers from the vestibular and reticular nuclei.

4th Ventricle and Rhomboid Fossa

• The 4th ventricle is a space between the medulla, pons, and cerebellum.
• The rhomboid fossa is the floor of the 4th ventricle.
• It's quadrangular in shape, with a lower triangle relating to the medulla oblongata and an upper triangle to the pons.

Cranial Nerves Emerging from the Medulla Oblongata

• Glossopharyngeal nerve (CN9)
• Vagus nerve (CN10)
• Accessory nerve (CN11)
• Hypoglossal nerve (CN12)

Nuclei in Brainstem (9-12)

• Specific nuclei are located within the medulla, responsible for functions like the motor functions of specific cranial nerves.

Nucleus Ambiguus

• The motor nucleus for cranial nerves 9, 10, and 11.
• It's a combination of the nuclei for the glossopharyngeal, vagus, and accessory nerves.

Nucleus of Trigeminal Nerve (CNV)

• Relates to pain and temperature sensation from the head and neck.
• Located in the pons, medulla, and upper spinal cord segments.
• At the medulla level, it's positioned posterolaterally.

Trigeminal Nerve Branches

• The trigeminal nerve innervates the face via three branches: ophthalmic, maxillary, and mandibular.

Pathway Nucleus

• This nucleus is associated with taste sensation, connecting to the facial (7th cranial nerve) and glossopharyngeal (9th cranial nerve) nerves.

Dorsal Nucleus of Vagus Nerve

• This nucleus is part of the parasympathetic nervous system, with nuclei in the vagus nerve.

Inferior Salivatory Nucleus

• This nucleus is located in the medulla oblongata and part of the parasympathetic system, associated with salivation from the glossopharyngeal nerve.

Brain Stem Cranial Nerves

• The brain stem houses several cranial nerve nuclei.
• Medulla oblongata, pons, and midbrain contain important centers for cranial nerve functions.

Vestibular Nuclei

• There are four vestibular nuclei (superior, inferior, medial, lateral).
• Medial and inferior vestibular nuclei are found within the medulla oblongata.

Nuclei at Medulla Level

• Varying nuclei (e.g., reticular, gigantocellular, parvocellular, paramedian) are found in various locations of the medulla.

Pyramidal Decussation

• The point where the pyramidal tracts cross from one side of the medulla to the other.

Levels of Pyramidal Decussation Through Inferior Olive

• Specific nuclei, like the cuneate, gracilis, spinal tract of the trigeminal nerve are present at varying levels through the medulla.