One of
the great challenges of CNS histology is to follow the progression from one
slide to another while knowing at which level the section was made. So, here
are a few pointers.
First, when looking
at the slides, the top of the page is dorsal, the bottom is ventral,
the center is medial and the sides are lateral. Also, if you
imagine you are travelling up the spinal cord, through the brainstem, to reach
the forebrain, you would be travelling in a caudal to rostral or posterior
to anterior direction. Slides 1 to 17 are layed out in a caudal to rostral
direction.
Below are listed landmark structures for each of the three main levels of
the brainstem:
1) Medulla:
- Major landmarks:
- inferior olive
- pyramids of the corticospinal tract
- cranial nerves X and XII.
- Lateral to the dorso-medial nuclei of XII is the dorso-motor nuclei
of X from which project parasympathetic neurons of X (careful: not
the motor nucleus of X). This is the nucleus ambiguus.
- Just above the lateral inferior cerebellar peduncles is the vestibular
nucleus.
|
|
2) Pons:
- Major landmarks:
- middle cerebellar peduncles
- 4th ventricule
- dentate nucleus of cerebellum
- cranial nerves V, VI, and VII
- The corticospinal tract is broken up in pieces within the pons.
- The trigeminal nerve appears as blue streaks; the main sensory
nucleus of V is lateral to the nerve whereas the motor
nucleus is medial to the nerve. More caudally, the abducens
and facial nerves are found, next to each other with the abducens
more medially located. The facial nerve originates laterally and wraps
around the abducens nucleus from below forming the facial colliculus.
|
3) Midbrain:
- Major landmarks:
- red nucleus
- cerebral peduncles
- central aqueduct
- cranial nerves III and IV
|
