Saturn Medic
Embryology (Head and Neck)
MCQ
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A newborn presents with midfacial and mandibular hypoplasia, defects of the first pharyngeal arch consistent with the diagnosis of Treacher Collins syndrome. What structure would most likely be involved with the syndrome?
The malleus is the only structure on this list derived from the neural crest of the first pharyngeal arch.
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Taste sensation from the oral part (anterior two-thirds) of the tongue is predominantly carried by
Taste sensation from the mucosa for the oral part of the tongue is carried by the chorda tympani branch of the facial nerve (CN VII). This part of the tongue forms from pharyngeal arch 1, so the trigeminal nerve (CN V) will carry sensory innervation from the mucosa
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During surgery for the removal of a thyroid tumor, a number of small masses of glandular tissue are noted just lateral to the thyroid gland. Metastasis from the thyroid tumor is suspected, but histological analysis of a biopsy reveals parathyroid tissue and remnants of thymus. How can this finding be explained?
The parathyroid and thymus migrate in a caudal and medial direction during development; therefore, ectopic glandular tissue may be found anywhere along the migratory path.
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Which pharyngeal arch is associated with Treacher Collins syndrome?
First arch syndrome results from abnormal development of pharyngeal arch 1 due to a lack of migration of neural crest cells. Treacher Collins syndrome is associated with underdevelopment of the zygomatic bone, down-slanting palpebral fissures, and deformed lower eyelids and external ears.
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The intermaxillary segment forms via the fusion of the
The intermaxillary segment, which plays a critical role in the formation of the definitive adult palate, forms when the two medial nasal prominences fuse in the midline.
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The most common site of a thyroglossal cyst is
The thyroid gland forms from a diverticulum in the midline of the floor of the pharynx. The thyroid migrates caudally and passes ventral to the hyoid bone. During this migration, the thyroid remains connected to the tongue by the thyroglossal duct. If a part of the thyroglossal duct persists, a cyst will develop, usually near the hyoid bone.
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The most common site of a pharyngeal fistula is the
A pharyngeal fistula forms when pharyngeal pouch 2 and pharyngeal groove 2 persist. Therefore, these fistulas are found on the lateral aspect of the neck, usually along the anterior border of the sternocleidomastoid muscle.
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What is the most common congenital malformation of the head and neck region?
Unilateral cleft lip is the most common congenital malformation of the head and neck. Cleft lip occurs when the maxillary prominences fail to fuse with the medial nasal prominences and when the underlying somitomeric mesoderm and neural crest fail to proliferate, resulting in a persistent labial groove. Cleft lip occurs in 1 of 900 births and may be unilateral or bilateral.
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