Superior colliculusOne of two bumps on the back of the midbrain. They are part of the tectum.
Cerebral aqueductThe narrow channel through the midbrain. Fluid passes along it to the fourth ventricle.
Periaqueductal grayA sleeve of gray matter around the cerebral aqueduct.
Tegmentum of the midbrainThe middle zone of the midbrain. It holds the red nuclei and runs on into the tegmentum of the pons.
Red nucleusA round nucleus in the tegmentum, one on each side. It shows in a cut at the superior colliculus.
Substantia nigraA band of pigmented cells in front of the tegmentum. It lies between the tegmentum and the crus cerebri.
Crus cerebriThe front part of each cerebral peduncle. Fibers from the cortex run down through it, among them the corticospinal tract.
Pons 6
Fourth ventricleThe fluid-filled space behind the pons. Its floor is the back of the pons and of the upper medulla.
Tegmentum of the ponsThe back part of the pons, under the fourth ventricle. It holds part of the reticular formation.
Basilar part of the ponsThe large front part of the pons. The pontine nuclei and the cross fibers lie in it.
Pontine nucleiSmall clusters of nerve cells in the basilar part. Their fibers cross the midline as the middle cerebellar peduncle.
Corticospinal fibersMotor fibers on their way from the cortex to the spinal cord. They run down through the basilar part to the pyramids.
Middle cerebellar peduncleA thick stalk from the pons to the cerebellum. There is one on each side, formed by fibers from the pontine nuclei.
Medulla 5
PyramidA bulge beside the front midline of the medulla. Motor fibers from the cortex run down in it.
Inferior olivary nucleusThe nucleus inside the olive. It makes the bulge on the side of the medulla.
Medial lemniscusA band of sensory fibers beside the midline, behind the pyramid. It carries fine touch and position sense upward.
Inferior cerebellar peduncleA stalk from the medulla to the cerebellum, one on each side. It lies beside the floor of the fourth ventricle.
Floor of the fourth ventricleThe back surface of the open medulla. Here the central canal has widened into the fourth ventricle.
How this list was compiled: Every name checked on 2026-10-01 in at least two of these. (1) Wikipedia, English edition, Midbrain, Pons, Medulla oblongata, Fourth ventricle and Corticospinal tract, https://en.wikipedia.org/wiki/Midbrain. (2) TeachMeAnatomy, The Midbrain, The Pons and The Medulla Oblongata, https://teachmeanatomy.info/neuroanatomy/brainstem/midbrain/. (3) Henry Gray, Anatomy of the Human Body, 20th edition (1918), https://archive.org/details/anatomyofhumanbo1918gray. Detail lines are in our own words. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
From the top of the sheet down: the midbrain, the pons, the medulla. The back of the brain stem is uppermost in each. Five small parts have a line; thirteen names go on the shapes themselves.
Read the full guide
Word bank, slice by slice
Midbrain, seven: superior colliculus, cerebral aqueduct, periaqueductal gray, tegmentum, red nucleus, substantia nigra, crus cerebri. Pons, six: fourth ventricle, tegmentum, basilar part, pontine nuclei, corticospinal fibers, middle cerebellar peduncle. Medulla, five: floor of the fourth ventricle, inferior cerebellar peduncle, inferior olivary nucleus, medial lemniscus, pyramid. Tegmentum is written twice.
Which slice is which
The midbrain has a small slit on the midline and two large circles under it. The pons is the widest, with an arm reaching up on each side and curved lines across its lower part. The medulla has a crinkled band on each side. The little side view in each corner takes no label.
Upside down, the midbrain slice is a bear's face: the two lower lobes are ears, the two circles eyes and the aqueduct a mouth.
Substantia nigra is Latin for black substance. Its cells make a great deal of melanin, which is why the band is drawn flecked.
Questions and answers
What is the difference between the tectum and the tegmentum?
Both are parts of the midbrain, named for where they lie against the cerebral aqueduct. The tectum, Latin for roof, is behind the aqueduct and carries the colliculi. The tegmentum is in front of it and is much the larger.
Is the crus cerebri the same as the cerebral peduncle?
Not quite. The crus cerebri is the front part of the peduncle, a bundle of fibers coming down from the cortex. The cerebral peduncle as a whole also takes in the tegmentum, and the substantia nigra lies between the two.
What is the difference between the open and the closed medulla?
In the open medulla, the upper part, the central canal has widened into the fourth ventricle, so its back surface is the floor of that ventricle. Lower down, in the closed medulla, the canal is still a tube inside. This slice is open.