Question

what are the external and internal features of the medulla?

what is the regional supply of the medulla

which specific trait/ nuclei are likely to be affected when blood supply to the lateral and medial part of the medulla is interrupted

If a patient complains of the following

a) loss of pain sensation over the right half of the face

b) loss of taste on the right half of the tongue

c) difficulty in hearing

Determine the structures involved and locate the lesion

Answer 1

External features of medulla

• The medulla is divided into right and left halves by the anterior and posterior median fissure.
• The anterior region is in the form of a longitudinal elevation called pyramid.The pyramid is made up of corticospinal fibers.
• Some fibers transversely across the upper part of the pyramid.Those are anterior external arcuate fibers.
• The upper part of the lateral region shows an oval elevation.It is produced by an underlying mass of grey matter called the inferior olivary nucleus.
• The rootlets of hypoglossal nerve emerge from anterolateral sulcus.
• The rootlets of cranial nerves IX and X emerge from posterolateral fissure.
• Lower part of medulla there is elevation the tuber cinerium lateral to the fasciculus cuneatus,
• The medulla is divided into two parts ,The lower closed part with a central canal.and upper open part where the central canal open.

Internal structures of medulla

can be explain with transverse sections. :-

Transverse section through the lower part of medulla passing through the pyramidal descussation

Grey matter

• The decussating pyramidal fibers seperate the anterior horn from central grey matter.It forms the spinal nucleus of accessory nerve laterally supraspinal nucleus for motor fibers of cervical nerve medially.
• Nucleus of spinal tract of trigeminal nerve.

​​​​​​​White matter

• The pyramids anteriorily
• Forms corticospinal tract

​​​​​​​transverse section through the middle of medulla

Grey matter

• The central grey matter contains

1. ​​​​​​​Hypoglossal nucleus
2. Dorsal nucleus
3. Nucleus of tractus solitarius

​​​​​​​White matter

• The nucleus gracilus and cuneatus gives rise to the internal accurate fibers.
• Emerging fibers of XII nerve

​​​​​​​Transverse section through the upper part of medulla pass ing through the floor of fourth ventricle.

Grey matter

• Nuclei of several nerves are seen

1. ​​​​​​​Hypoglossal nucleus
2. Dorsal nucleus of vagus
3. Nucleus of tractus solitarius

• ​​​​​​​The nucleus ambigus gives origin to cranial nerves IX,X, and XI.
• The dorsal and ventral nuclei recieve fibres from cochlear nerve.

​​​​​​​White matter

• The olivocerebellar fibers are seen prominently in actual sections,
• Striae medullaris are seen
• Emerging fibers of IX,X, and XI nerves.

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