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Position of medulla oblangata in the human brain
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Section of the medulla oblongata at about the middle of the olive
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The is the lower portion of the
Brainstem . By
Anatomical Terms Of Location , it is rostral to the
Spinal Cord and caudal to the
Pons , which is in turn ventral to the
Cerebellum . For a human or other
Biped al species, this means it is above the spinal cord, below the pons, and anterior to the cerebellum. It controls
Autonomic functions and relays nerve signals between the
Brain and
Spinal Cord .
The medulla is often thought of as being in two parts, an open part (close to the pons), and a closed part (further down towards the
Spinal Cord ). The 'opening' referred to is on the dorsal side of the medulla, and forms part of the fourth
Ventricle of the brain.
Running down the ventral aspect of the medulla are the ''pyramids'' which contain corticospinal fibres. On the open medulla, there is a slight bulge just behind the pyramids called the ''olive'' or
Olivary Nuclei .
Cranial Nerve XII (the
Hypoglossal Nerve ) emerges between these two structures. Cranial nerves IX and X (
Glossopharyngeal and
Vagus Nerve s) also emerge from the medulla.
The base of the medulla is defined by the commissural fibres, crossing over from the ipsilateral side in the spinal cord to the contralateral side in the brain stem - below this is the spinal cord.
# To control autonomic functions (such as breathing and heartbeat)
# To relay nerve messages from the brain to the spinal cord
# Processing of inter-aural time differences for
Sound Localization (olivary nuclei)
# Function control of sneeze-, cough-, swallow-, suck-reflex and of vomiting.
Blood to the medulla is supplied by a number of arteries.
The anterior spinal artery supplies the whole medial part of the medulla oblongata. A blockage (such as in a
Stroke ) will injure the
Pyramidal Tract ,
Medial Lemniscus and the
Hypoglossal Nucleus . This causes a syndrome called ''
Medial Medullary Syndrome ''.
The posterior inferior cerebellar artery, a major branch of the vertebral artery, supplies the posterolateral part of the medulla, where the main sensory tracts run and
Synapse . (As the name implies, it also supplies some of the
Cerebellum .)
The vertebral artery supplies an area between the other two main arteries, including the
Nucleus Solitarius and other sensory nuclei and fibres.
Lateral Medullary Syndrome can be caused by occlusion of either the PICA or the vertebral arteries.
