Lab 8 - Higher Motor Function

Gross Anatomy - Anterior Aspect

On the anterior surface of the brain stem note the blood vessels of the circle of Willis, the cerebral peduncles (crus cerebri) of the midbrain, and the mammillary bodies of the diencephalon.

Notice the large oculomotor nerves emerging from the interpeduncular fossa. More rostrally, notice that the optic nerves course caudally along the orbital surface of the frontal lobes and join at the optic chiasm, rostral to the infundibulum. The olfactory bulbs and tracts can be seen between the orbital gyrus and gyrus rectus of the frontal lobe. The medullary pyramids can be seen near the midline caudal toGross Anatomy - Anterior Aspect the pons.

Note the course of the cerebral peduncles into the core of the cerebrum. Notice the medialgeniculate body of the thalamus located posterior to the cerebral peduncle

Examine the cut edge of the midbrain and look for the black band formed by the substantia nigra. It is located just posterior to the crus cerebri. Locate the two large reddish-gray structures, thered nuclei, situated along the midline just posterior to the substantia nigra. Observe the small channel formed by the cerebral aqueduct, just anterior to the midbrain tectum.