The lowest part of the brainstem, continuous with the spinal cord at the foramen magnum
Medulla oblongata — 'oblong marrow' in Latin.
Anatomy · Brain & nerves
Medulla oblongata
Lowest part of the brainstem
Brain · brainstem (lowest part)
The lowest part of the brainstem, about 3 cm long, running from the pons down to where it meets the spinal cord at the foramen magnum. It contains the vital centres for breathing, heart rate and blood pressure, and reflexes such as coughing, vomiting, sneezing and swallowing. On its front surface the pyramids carry the motor pathways, most of which cross to the opposite side here.
How to spot them
- ▸A short, slightly conical piece of brainstem below the bulge of the pons, blending into the spinal cord
- ▸Two ridges called pyramids run down the front, with an oval swelling (the olive) on each side
- ▸The lower part contains a central canal; the upper part opens into the floor of the fourth ventricle
- ▸The point where lower cranial nerves IX–XII emerge, in a row beside the olive
What to know
Contains the centres that control breathing, heart rate and blood pressure, so damage here is rapidly fatal
Medulla oblongata — the cardiovascular and respiratory centres.
About nine-tenths of the descending motor fibres cross to the opposite side here, at the decussation of the pyramids
Medulla oblongata — why the left brain moves the right hand.
Bears a pair of ridges on its front called pyramids and an oval bump on each side called the olive
Medulla oblongata — the olive contains the inferior olivary nucleus.
Coordinates the reflexes of vomiting, coughing, sneezing and swallowing
Medulla oblongata — several reflex centres are located here.
The origin of cranial nerves IX, X and XII, and the cranial part of XI
Medulla oblongata — the glossopharyngeal, vagus, accessory and hypoglossal nerves.
A stroke in the posterior inferior cerebellar artery territory here causes a syndrome of dizziness, hoarseness and crossed loss of pain and temperature
Medulla oblongata — lateral medullary (Wallenberg) syndrome.
Key ideas
- The crossing of the pyramidal fibres explains why each side of the brain controls the opposite side of the body.
- Its cardiovascular and respiratory centres are why herniation of the cerebellar tonsils through the foramen magnum can cause sudden death.
Quick-fire facts
- •About 3 cm long, the smallest and lowest of the three brainstem parts
- •Name is Latin for 'oblong marrow', a reference to its shape
- •Cranial nerves IX, X, XII arise from it, and the cranial root of XI
- •Around 90 per cent of pyramidal fibres cross at the decussation of the pyramids, giving each hemisphere control of the opposite side
- •Houses the cardiovascular centre and the dorsal respiratory group, which set the basic rhythm of breathing
- •Its lower part contains a central canal, continuous with that of the spinal cord; its upper part forms the lower floor of the fourth ventricle
- •Wallenberg's lateral medullary syndrome follows blockage of the vertebral or posterior inferior cerebellar artery
- •The gracile and cuneate nuclei here relay touch and proprioception from the body
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Sources
- TeachMeAnatomy — Medulla oblongata
- OpenStax — 13.2 The Central Nervous System — Anatomy and Physiology 2e