Side by side
| Compared | Pons | Medulla oblongata |
|---|---|---|
| Where it is | Below the midbrain, above the medulla oblongata and in front of the cerebellum; its back surface forms the upper part of the floor of the fourth ventricle. [1][5] | The lower part of the brainstem, in front of and partly below the cerebellum; at its lower end it continues as the spinal cord at the foramen magnum. [2][3] |
| What it does | Relays signals from the forebrain to the cerebellum; its pontine respiratory group regulates the switch from breathing in to breathing out. [1][6] | Holds the cardiovascular, respiratory, vomiting and vasomotor centres; its dorsal and ventral respiratory groups set the basic rhythm of breathing. [2][6] |
| Connects with | Pontine nuclei pass signals from the cortex to the opposite side of the cerebellum through the middle cerebellar peduncles; nuclei of cranial nerves V to VIII lie in it. [1][7] | Most voluntary-movement (corticospinal) fibres cross sides here, at the decussation of the pyramids; the inferior cerebellar peduncles link it to the cerebellum; nuclei of cranial nerves IX to XII lie in it. [2][8][9] |
| Size measured from the model | 34 mm front to back, 29 mm top to bottom, 42 mm side to side [4] | 33 mm front to back, 41 mm top to bottom, 27 mm side to side [4] |
Size is the box each part fits in on this one model (pons; medulla oblongata), not its volume. Real brains vary.
How far apart are they?
Measured from the model [4], from the pons to the medulla oblongata:
- Centre to centre: 24 mm in a straight line.
- The centre of the medulla oblongata is 9 mm further back, 22 mm lower and the same distance from the midline than the centre of the pons.
- Nearest points of the two shapes: under 1 mm apart.
A “centre” here is the average position of the points on the part’s 3D surface, so for a curved part such as a C shape it can sit outside the part itself. The nearest-points figure is measured between the corners of the simplified meshes, so a gap of 2 or 3 mm or less is within the model’s coarseness: read it as “touching or nearly so”.