The brain cut level, as on an axial scan, through the basal ganglia and the thalamus: the face of the cut, computed from the 3D model this site uses, seen from above. Below it, the same slice blank and numbered, with an answer key.
Horizontal (axial) section: the brain cut level through the basal ganglia
Horizontal section through the basal ganglia and the upper half of the thalamus, seen from above; the front of the brain at the top, the brain’s left half on the left of the sheet. 20 parts labelled.
Drawn from BodyParts3D, (c) The Database Center for Life Science, CC BY-SA 2.1 JP. Diagram: brainlocation.com/diagram/, shared under CC BY-SA 2.1 JP (credits). For learning, not medical advice.
Horizontal section, blank: name the 20 numbered parts
Horizontal section through the basal ganglia and the upper half of the thalamus, seen from above; the front of the brain at the top, the brain’s left half on the left of the sheet.
Drawn from BodyParts3D, (c) The Database Center for Life Science, CC BY-SA 2.1 JP. Diagram: brainlocation.com/diagram/, shared under CC BY-SA 2.1 JP (credits). For learning, not medical advice.
Which cut this is
A horizontal (axial or transverse) plane runs parallel to the ground when you stand and splits the brain into an upper and a lower part; this sheet shows the face of the lower part, looked at from above. The other standard views are on the labelled diagram (side, midline, underside) and the coronal section.
This is the classic level for the internal capsule: on each side it is a white wedge bent like a chevron, with the caudate nucleus in front of the bend, the thalamus behind it and the putamen and globus pallidus on its outer side.
The front horns of the lateral ventricles lie side by side at the front, separated by the septum, with the corpus callosum curving round in front of them; the corpus callosum shows again at the back, between the occipital ends of the hemispheres.
The third ventricle is the slit between the two thalami; the fornix shows as small patches at its front end and again behind the thalami, beside the back of the lateral ventricles.
Outside the putamen comes the insula, and outside that the superior temporal gyrus; the frontal lobe fills the top of the sheet and the occipital lobe the bottom.
How it is drawn
The shapes are not traced by hand: the BodyParts3D meshes the 3D brain on this site shows are cut on one flat plane, on a grid of 0.25 mm cells. For each part the plane passes through, the half beyond the cut is removed and the rest is depth-buffered from the cut side, as the midline view is; a cell belongs to the part when the first surface of that part the eye meets is the inside of its far wall, which only happens when the cell lies within it. Where a cell is inside two parts (a nucleus within the white matter) the smaller, inner one wins.
So only parts the cut really passes through are drawn, and every label names one of them: test/diagram.test.cjs rebuilds the cut, and for each label checks that its dot lies inside the outline drawn for that part and inside the part's own 3D shape, tested on its own by casting rays from the dot in six directions.
The claustrum and the external capsule have no shape of their own in the model; they are part of the white matter between the putamen and the insula. In the model the middle frontal gyrus lies wholly above this level, so it is not on the sheet.
Parts the atlas has no shape for at all (the substantia nigra and red nucleus inside the midbrain, the thalamic nuclei) are not drawn; their pages light the part that holds them. The tentorium, a fold of the brain’s outer covering, is in the model but left off: it is not brain.
It is one adult brain, with small gaps where the model’s shapes do not quite meet (left white). Real brains differ, and a slide or scan a few millimetres further forward or back shows the parts in other proportions, so learn the order of the parts rather than their exact shapes.
The drawing is derived from BodyParts3D and carries its licence, CC BY-SA 2.1 Japan: copy, hand out and reuse it with the credit line. Standalone SVG files: labelled, blank.
