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Let’s start our USMLE Review with Anatomy from the Gold Standard USMLE Step 1 Audio Review program.
Play USMLE Audio MP3 26 16 Pons (1_5) Below
Begin 26 16 Pons (1_5) Transcription
Alright, moving on now to number 10, the pons.
The pons are located, in general terms, about where?
- Between the midbrain and the medulla.
Now they contain two what main groups of nuclei?
- The auditory and vestibular nuclei.
And these auditory and vestibular nuclei in the pons are involved in regulation of what reflexes and mechanisms?
- The vestibulo-ocular reflexes and postural mechanisms.
Let’s take a look at the internal anatomy of the pons, the rostral pons first, and please refer to figure 10.1.
Student doctor, what three tracts are located in the basilar part of the pons?
- The corticospinal, the corticopontine, and the pontine nuclei.
Student doctor, where are the principal sensory and motor nuclei of the trigeminal nerve located?
- In the posterolateral tegmentum.
Now the motor nucleus is where?
- Medial to the principal nucleus.
Student doctor, where is the mesencephalic nucleus of the trigeminal nerve located?
- It is dorsal to the motor nucleus and principal sensory nucleus.
Student doctor, what do the cells of the raphe nuclei, which is part of the pontine reticular formation, synthesize?
- They synthesize serotonin.
And what do the cells of the locus coeruleus synthesize?
- They synthesize norepinephrine.
Now four cranial nerves exit from the ventral surface of the pons. Student doctor, list these four cranial nerves which exits from the ventral surface of the pons. In each case, give the name and number, and we’ll take these in order by number.
First, the trigeminal nerve, which is cranial nerve V.
Second, the abducens nerve, which is cranial nerve VI.
Third, the facial nerve, which is cranial nerve VII. And
fourth, the vestibulocochlear nerve, which is cranial nerve VIII.
From where do these four cranial nerves: the trigeminal nerve (CN V), the abducens nerve (CN VI), the facial nerve (CN VII) and the vestibulocochlear nerve (CN VIII), where do they exit from in the pons?
- From the ventral surface of the pons.
Now where do CN VII and VIII attach?
- They attach at the pontocerebellar angle.
And how do CN VII and VIII relate to each other?
- CN VII, the facial nerve, is medial to the CN VIII.
Now where does the trigeminal nerve, CN V, attach?
- It attaches in the middle of the pons on the surface of the middle cerebellar peduncle.
Student doctor, where in the pons is the nucleus of the abducens nerve located?
- The abducens nerve is located near the midline at the junction between the medulla and the pons.
Student doctor, what nucleus of the facial nerve, give rise to the SVE, that’s the special visceral efferent fibers, that innervates the muscles of facial expressions?
- The facial nucleus of CN VII also gives rise to special visceral efferent fibers (SVE) which innervates the muscles of facial expression.
Now the superior salivatory nucleus of CN VII gives rise to GVE fibers, that’s general visceral efferent fibers, that synapse in what two ganglia? In the pterygopalatine and submandibular ganglia.
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