Pons - Neuroanatomy Lab Spring 2025

false -- they are horizontal cross sections because the pons is not a bent structure

True or False: Cross sections of the pons are angled just like the mesencephalon?

basilar artery

What artery runs along the base of the pons?

basilar sulcus

What sulcus does the basilar artery run in?

posterior cerebral

What artery does the basilar artery decussate into at the base of the circle of willis?

pons

The middle cerebellar peduncle hugs what structure?

pons to cerebellum

Middle cerebellar peduncles go from ______ to _____

the trigeminal nerve

Where ______ exits the pons separates the base of the pons from the middle cerebellar peduncle (brachium pontis) of the pons?

lateral side

What aspect of the pons does the trigeminal nerve exit the pons?

tegmentum of the mesencephalon

Tegmentum of the pons is continuous with what structure of the mesencephalon?

no -- d/t the cerebellum

Does the pons have a tectum like the mesencephalon does? why?

4th ventricle

What is the fluid filled space that the aqueduct of sylvius (in the mesencephalon) flows into?

-superior medullary vellum

-cerebellum

-inferior medullary vellum

What are the 3 components that the roof of the 4th ventricle is made out of?

the pons

What makes up a large portion of the floor of the 4th ventricle?

-ascending sensory pathways (same as tegmentum of mesencephalon)

-cranial nerve nuclei for V, VI, VII, VIII

What is the tegmentum of the pons the location of?

-descending motor fibers from the crus cerebri of mesencephalon

-pontine nuclei (pontocerebellar tract)

What is the base of the pons the location of?

decussating auditory fibers

What is present is the trapezoid body of the pons?

-pons

-cerebellum

-medulla oblongata

The 4th ventricle is the major ventricular system for what structures of the brain?

spinal canal

The 4th ventricle will become the what of the spinal cord?

First it will start to get larger, starts to get smaller at the pontomedullaary junction

How does the 4th ventricle change as we move cranial to caudal in cross sections?

larger

As we move down the brainstem through the pons, the middle cerebellar peduncles will start to get (smaller/larger)

abducens (VI) and facial (VII) nucleus

What GSE nerve nucleus are present on the midline of the pons right next to the 4th ventricle?

1) Size of the middle cerebellar peduncle

2) Size of the fourth ventricle

What are the 2 important keys to knowing the level of the sections through the pons?

CN IV

What nerve runs in the superior medullary vellum of the pons?

pontomedullary junction

What is the most caudal portion of the pons?

1) Base of the pons -- do not see transverse fibers

2) Massive 4th ventricle

3) Longitudinal fibers are clustered

4) VI, VII, VIII CNs come off the pons in this region

How do we know we are in the pontomedullary junction of the brain (most caudal portion of the pons) on an MRI section?

CN 6,7,8

What nerves come off the pons laterally in the section of the pontomedullary junction?

medially

Where does CN 6 come off the pons?

more laterally, they come off together because they both enter the internal acoustic meatus

Where do CN 7 and CN 8 come off the pons?

pontomedullary junction

Where is the only spot of the brain where 3 CNs will be coming off the brainstem in the same plane?

within the floor of the 4th ventricle

Where is the facial colliculus in the pons?

-GSE of abducens

-fascicles of facial nerve

What is present in the facial colliculus?

-hemifacial flaccid paralysis of the face

-6th nerve palsy (abducens)

What happens if you push on the facial colliculus?

no -- only SVE motor fibers are present in this turn

If you push on the facial colliculus of the pons, would parasympathetic fibers of CN 7 be affected?

BA 4 -- Layer 5

Where are the initiating cell bodies of the longitudinal fibers present in the pons?

posterior limb of the internal capsule

What limb of the internal capsule do descending motor fibers from the primary motor cortex pass through?

Crus cerebri of the mesencephalon and longitudinal fibers in the base of the pons

After the posterior limb of the anterior capsule, where do the descending motor fibers pass through the mesencephalon and pons?

through the pyramids

Where do the descending motor fibers pass through the medulla oblongata?

LATERAL CORTICOSPINAL: decusatation of the fibers and then descend contralaterally

ANTERIOR CORTICOSPINAL: straight through the pyramids and then decussate in the spinal cord level of the muscle

What happens after descending motor fibers descend through the medullary pyramids?

base of the pons

Where do the transverse fibers of the pons decussate?

transverse fibers

Pontine nuclei create what types of fibers?

left

Right pontine nuclei decussate to the _____ middle cerebellar peduncle (cerebellum)

intention tremor

What kind of tremor is associated with spinocerebellar circuit damage?