CerebrumBy far the largest part of a pig's brain. Two long hemispheres, widest toward the back. Their surface is folded into ridges and grooves, fewer than in a horse or a cow.
Longitudinal fissureThe deep groove down the middle. It separates the two hemispheres of the cerebrum.
CerebellumThe ridged part behind the cerebrum. In a pig it is very wide and short. It makes movements smooth and exact.
VermisThe middle strip of the cerebellum, between its two side lobes. It is large in the pig.
Medulla oblongataThe hindmost part of the brain, relatively broad in the pig. It carries on into the spinal cord and looks after heart rate and digestion.
Olfactory bulbsThe pair of lobes at the front that deal with smell. They are very large in the pig.
Spinal cordThe thick cord of nerve tissue from the brain down the backbone.
The fish 6
Optic lobesThe two lobes of the midbrain, the largest part of this brain. They deal with what the eyes see.
CerebrumA small pair of hemispheres. In a fish they deal largely with smell, and they are far smaller than the optic lobes.
CerebellumA single lobe behind the optic lobes. It keeps the fish balanced and its swimming smooth.
Medulla oblongataThe hindmost part of the brain, which narrows into the spinal cord.
Olfactory lobesThe pair of lobes at the front. They take in the signals of smell from the nostrils.
Spinal cordThe cord of nerve tissue from the brain. It runs through the arches of the backbone.
The shark 6
Olfactory bulbsTwo large round lobes of smell at the front. Each is on a stalk. They are remarkably large in a dogfish.
CerebrumThe pair of cerebral hemispheres. In a fish they deal largely with smell.
Optic lobesThe two rounded lobes of the midbrain. They deal with sight and with other senses.
CerebellumA long single lobe that reaches back over the medulla. It keeps the shark balanced and its movements in step.
Medulla oblongataThe long hindmost part of the brain. It carries on into the spinal cord.
Spinal cordThe cord of nerve tissue that carries on from the medulla.
How this list was compiled: Every name checked on 2026-09-30 in two sources. Pig: S. Sisson, The Anatomy of the Domestic Animals (1914, public domain), https://archive.org/details/anatomyofdomesti00siss, with L. H. Hyman's laboratory manual and Wikipedia, Brain. Fish: R. W. Hegner, College Zoology (1912, public domain), the perch, https://archive.org/details/collegezoology00hegn, and Wikipedia, Fish anatomy. Shark: L. H. Hyman, A Laboratory Manual for Comparative Vertebrate Anatomy (1922, public domain), the dogfish, https://archive.org/details/ost-biology-labmanualcompvert00hymarich, with Hegner (1912) and Wikipedia, Shark. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work
How it works
This pig brain diagram shows the brain from above, front to the left. Two more views give a fish and a shark. The parts come in the same order in all three; what changes is how much room each one takes.
Read the full guide
The pig
From the front: the olfactory bulbs, the two hemispheres of the cerebrum with the longitudinal fissure between them, the cerebellum with the vermis down its middle, the medulla oblongata and the spinal cord. The cerebrum is by far the largest part, and its surface is folded.
Fish and shark
The fish brain diagram has a small smooth cerebrum and optic lobes larger than any other part. The shark brain diagram has two large olfactory bulbs on stalks, and a long cerebellum. Press Quiz me to name each part yourself.
Read each brain from left to right: smell at the front, then the cerebrum, the optic lobes where they show, the cerebellum and the medulla.
Questions and answers
What is the largest part of a pig's brain?
The cerebrum. Its two hemispheres cover most of the brain when it is seen from above, and their surface is folded into ridges and grooves.
How is a fish brain different from a pig brain?
A fish has a small, smooth cerebrum, and its optic lobes, the part that deals with sight, are the largest part of the brain. In a pig the folded cerebrum covers that region completely.
Why are a shark's olfactory bulbs so large?
They deal with smell, which many sharks rely on to find food. The size of the bulbs varies from one kind of shark to another with how much it depends on smell.
Do a pig, a fish and a shark have the same brain parts?
They have the same main parts in the same order: lobes of smell, cerebrum, midbrain, cerebellum and medulla. The sizes differ greatly.