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Thursday, October 09, 2008

Facial Nucleus / Facial Colliculus seen in Pons

Question 13
Facial Nucleus / Facial Colliculus seen in
a.       Midbrain
b.      Pons
c.       Medulla
d.      Interpeduncular fossa
Answer
b) Pons
Reference:
Gray 38th Edition 1243
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Discussion
The nucleus from which most facial motor fibres are derived lies deep in the reticular formation of the caudal part of the pons, posterior to the dorsal trapezoid nucleus and ventromedial to the spinal tract nucleus of the trigeminal nerve. It represents the branchial efferent column but lies deeper in the pons than might be expected and its efferent fibres have a most unusual course. Both these features have been explained by invoking neurobiotaxis.
Explanation
Self Explanatory
Comments
The nucleus receives fibres from both corticonuclear tracts in the lower pons and is reputedly supplied by aberrant pyramidal fibres which descend in the medial lemniscus. The facial motor nucleus is a complex consisting of lateral, intermediate and medial subnuclei The lateral subnucleus is said to innervate the buccal musculature, the intermediate sends axons into the temporal, orbital and zygomatic facial branches and the medial group into the posterior auricular and cervical rami and probably the stapedial nerve. Nuclear lesions have produced a roughly similar but more detailed schema
Tips
Sensory Nucleus is the rostral end of the nucleus solitarius in the medulla oblongata. It receives gustatory and possibly other afferents from the sensory root and sends fibres to the contralateral ventral lateral thalamic nuclei. As they ascend in the midbrain and subthalamic regions, these fibres pass near the midline.
The sensory root also contains efferent preganglionic parasympathetic fibres for the submandibular and sublingual salivary glands, lacrimal gland, and pharyngeal, nasal and palatine glands.

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