USMLE Step 1 Neuroanatomy Review 27 03 The Caudal Medulla

USMLE Step 1 Neuroanatomy Review 27 03 The Caudal Medulla

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Play USMLE Audio MP3 27 03 The Caudal Medulla Below

 

Begin 27 03 The Caudal Medulla Transcription

All right, now we’re going to take a look at the caudal medulla.  Please refer to figure 11.2

The pyramidal tracts are located in what part of the medulla?

  • In the anterolateral part.

Now, 80% of the fibers in the pyramidal tracts decussate and continue in what manner as what tract? 

  • Contralaterally as the lateral corticospinal tract.

Now, the other 15% of the fibers continue as what tract?

  • As the anterior corticospinal tract.

Student doctor, what is the structure that encircles the central canal? 

  • This is called the central gray. 

 Now, what structure of the spinal cord is analogous to the spinal nucleus of cranial nerve five? 

  • Another way of putting this question is, the spinal nucleus of cranial nerve five is the posterior analogue of what spinal structure?  Substantia gelatinosa of the spinal cord.

  Student doctor, where is the spinal tract of cranial nerve five located? 

  • The spinal tract of cranial nerve five lies lateral to the spinal nucleus of cranial nerve five.

  Now, it extends from where to where? 

  • From the upper cervical cord to the midpons.

 Student doctor, what sensations are carried through the spinal tract of cranial nerve five? 

  • The spinal tract of cranial nerve five receives pain and temperature sensation from the face. 

  Student doctor, where is the hypoglossal nucleus located? 

  • The hypoglossal nucleus is located in the posterior tegmentum near the midline.

  Now, where is the dorsal motor nucleus of cranial nerve ten located? 

  • It is located lateral to the nucleus of cranial nerve twelve. 

  The dorsal motor nucleus of cranial nerve ten gives rise to what fibers? 

  • Preganglionic parasympathetic fibers.

  Student doctor, where is the medial longitudinal fasciculus, the MLF, located? 

  • The MLF is located in the posterior tegmentum. 

  From where to where? 

  • From the upper cervical cord to the midbrain.

  Now the MLF connects a number of structures together.  Please pause if you wish and list them.  The MLF connects the ocular nuclei of cranial nerves three, four, and six together and input from the vestibular nuclei, cerebellar and proprioceptive fibers from the neck.  Now, it also helps in coordinate of what movement of what structure? 

  • The MLF helps in the coordination of eye movements.  Now the MLF also contains what kinds of fibers of what other cranial nerves?  The MLF also contains vestibular fibers of cranial nerves eight, three, four, and six.

  Student doctor, where in the medulla is the fasciculus gracilis located? 

  • The fasciculus gracilis is located medially.

  And, where is the fasciculus cuneatus located? 

  • The fasciculus cuneatus is located laterally.

 Now, the axons of the fasciculus gracilis and the fasciculus cuneatus both terminate in what two structures, respectively? 

  • In the nucleus gracilis and the nucleus cuneatus respectively.

 Now, they also send axons that decussate in what structure? 

  • In the caudal medulla.

And these axons then do what? 

  • They ascend in the medial lemniscus.

****END OF TRANSCRIPTION****

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