1. A 61-year-old female complains of coughing when she swallows. Her physical examination reveals weakness in elevating the floor of the mouth and larynx. Provide a developmental account for the adult anatomy, innervation, and function of the digastric muscle. (6 pts)

Anatomy and Development

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Innervation and Function

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2. A 31-year-old male complains of a dry mouth. His physical examination reveals bruising along the neck of the mandible. The patient reported being hit by a wildly pitched baseball. A disruption of the nervous supply to the parotid gland is highly suspected. Discuss the anatomy of the otic ganglion and its preganglionic and postganglionic nervous pathways. (6 pts)

Anatomy

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Nervous Pathways

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3. A 46-year-old male complains of double vision and sensitivity to light. His physical examination reveals a dilated right pupil. Double vision is present on downward gaze. Entrapment of the inferior division of the oculomotor nerve at the annulus tendineus is highly suspected. Discuss the anatomy of the annulus tendineus and cite the structures that pass through it. (6 pts)

Anatomy

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Contents

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4. A 50-year-old male complains of neck pain and shortness of breath. His tongue is elevated and posteriorly displaced. His neck has firm edema and is warm and tender to the touch. He has multiple deep dental caries. You hear a high pitched noise (stridor) in his neck but not in his lungs. An X-ray of his teeth shows an apical abscess on the lower left second molar. Ludwig's angina is highly suspected. Discuss the boundaries, relationships, and significance of the retropharyngeal space. (6 pts)

Boundaries

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Relationships

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Significance

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5. A 45-year-old female complains of numbness along the left side of her chin and tongue. Her physical examination reveals a unilateral loss of touch sensation to the anterior two-thirds of her tongue. Nevertheless, her ability to taste is unimpaired. A tumor of the left mandibular nerve at the foramen ovale is highly suspected. Provide a developmental account for the adult anatomy, function, and innervation of the tongue. (6 pts)

Development and Innervation

Summary comment. At the end of the 4th week, the tongue develops from the floor of the primordial pharynx in the region of the paired pharyngeal arches. In summary, the pharyngeal arches give rise to the mucosa of the tongue while occipital somites give rise to the tongue musculature (except for the palatoglossus muscle).

• 1st pharyngeal arch:
  1. Gives rise to lateral lingual swellings and median tongue bud
  2. Lateral lingual swellings develop into mucosa of anterior 2/3 of tongue because of its rapid outgrowth
  3. Trigeminal nerve grows into arch 1 and therefore supplies this region for touch, temp, pain
     • Lingual branch of mandibular division of trigeminal (GSA)]
• 2nd Pharyngeal arch:
  1. Gives rise to the copula of the tongue which is overgrown by other regions of the developing tongue
  2. The remnant of this arch is the nerve that supplies into arch 2
     • The chorda tympani (specifically the SVA components) off of the facial nerve which innervates all taste buds except the vallate papillae. The GVE components travel to the submandibular gland, sublingual gland, and mucosa of the tongue.
• 3rd Pharyngeal arch:
  1. Contributes to the majority of the hypoharyngeal eminence which will give rise to the mucosa of the majority of the posterior 1/3 of the tongue
  2. The arch 3 nerve, the glossopharyngeal, will supply all sensory innervation to the most of the posterior 1/3 of the tongue, including taste (GVA)
• 4th Pharyngeal arch:
  1. Contributes to the small dorsal part of the hypopharyngeal eminence and the epiglottis
  2. The arch 4 nerve, the superior laryngeal branch of the vagus will do sensory innervation of the most posterior region of the posterior 1/3 of the tongue and the epiglottis (GVA)
• Intrinsic and extrinsic muscles of the tongue:
  1. Occipital or Post-otic somites give rise to the intrinsic and extrinsic muscles of the tongue by migrating inferiorly and medially. These migrating somites drag with it the hypoglossal nerve (GSE), which, therefore, innervates all the intrinsic and extrinsic muscles of the tongue EXCEPT palatoglossus which is innervated by the pharyngeal plexus of the vagus nerve

Anatomy

• The boundary between the first and third arch contributions to the tongue (or the anterior 2/3 and posterior 1/3 of the tongue) is the terminal sulcus. The evidence of fusion of the two lateral lingual swellings is the marked by the midline groove known as the median sulcus. The point at which these two sulci meet is known as the foramen cecum which is the location of origin of the thyroid gland.

Function

• The tongue's primary functions are in taste and manipulation of food during mastication (to enhance chewing and transmit a food bolus into the pharynx/gut tube). The tongue plays a secondary role in speech.