Ventral Brainstem


Brain Dissection


Pyramids


Half Brain
Myelencephalon (medulla oblongata)
Components:       [NOTE: * = not paired]
• pyramids (corticospinal fiber tracts)
• trapezoid body * (auditory fibers & nuclei)
• various nuclei, tracts, & reticular formation
• fourth ventricle* (caudal medullary vellum*= roof of the ventricle)
• cranial nerves:
abducent n. (VI)
facial n. (VII)
vestibulocochlear n. (VIII)
glossopharyngeal n. (IX)
vagus n. (X)
accessory n. (XI)
hypoglossal n. (XII)

Surface Features . . .
Ventral surface:
• pyramids
• trapezoid body*
• cranial nerves (VI through XII)

Dorsal surface:
• fourth ventricle* (including: caudal medullary vellum* & choroid plexus)
• obex*
• nucleus gracilis
• medial & lateral cuneate nuclei
• spinal tract of the trigeminal nerve

Lateral surface:
• pyramid (also, pyramidal decussation)
• trapezoid body*
• cranial nerves (VI, VII, & VIII)

Median surface:
• pyramid (also, pyramidal decussation)
• nuclei, tracts, & reticular formations
• fourth ventricle* (including: caudal medullary vellum* & choroid plexus)

Typical-sections Features . . .
Rostral level:
• pyramids
• cochlear nuclei (ventral & dorsal)
• dorsal nucleus of trapezoid body
• cranial nerve nuclei & fibers (VI, VII, & VIII)

Caudal level:
• pyramids
• pyramidal decussation*
• olivary nucleus
• lateral cuneate nucleu
• medial cuneate nucleus
• nucleus gracilis
• cranial nerve nuclei & fibers (X & XII)

Go Top