A 64-year-old man loses consciousness near the entrance to an emergency room. A physician rushes to the patient and palpates a strong pulse along the inner side of the left sternocleidomastoid muscle. The vessel palpated by the doctor is a derivative of which of the following aortic arches?

Question

A 64-year-old man loses consciousness near the entrance to an emergency room.  A physician rushes to the patient and palpates a strong pulse along the inner side of the left sternocleidomastoid muscle.  The vessel palpated by the doctor is a derivative of which of the following aortic arches?

Quizplus · Accepted Answer

11ec160b_3735_b2ce_9249_978b2010d6c3_MD0001_00 During embryonic development, the head, neck, and upper thorax region develop from a set of arches known as pharyngeal arches. Each arch is associated with a cranial nerve and an aortic arch derivative. The vessel palpated in this patient is the common carotid artery, which (along with the proximal portion of the internal carotid artery) is derived from the third aortic arch (ie, third pharyngeal arch). The third pharyngeal arch also gives rise to the glossopharyngeal nerve (CN IX), parts of the hyoid bone, and the stylopharyngeus muscle. (Choice A) The first pharyngeal arch is associated with the trigeminal nerve (CN V). This pharyngeal arch gives rise to the tensor tympani, muscles of mastication, maxilla, and inner ear bones (eg, incus, malleus). The associated first aortic arch regresses almost completely, although it does give rise to a portion of the maxillary artery. (Choice B) The second pharyngeal arch is associated with the facial nerve (CN VII). This pharyngeal arch gives rise to the muscles of facial expression as well as some ear and hyoid structures. The stapedial artery is a derivative of the associated second aortic arch, but this vessel typically regresses. (Choice D) The fourth pharyngeal arch is associated with the superior laryngeal branch of the vagus nerve (CN X). This pharyngeal arch gives rise to many of the muscles of the pharynx and soft palate as well as a few of the laryngeal muscles. The associated fourth aortic arch gives rise to part of the true aortic arch and subclavian arteries. (Choice E) The sixth pharyngeal arch is associated with the recurrent laryngeal branches of CN X. This pharyngeal arch gives rise to most of the muscles of the larynx, and the associated aortic arch gives rise to the pulmonary arteries and the ductus arteriosus. Educational objective: The common carotid artery and the proximal portion of the internal carotid artery are derived from the third aortic arch. The third aortic arch is associated with the third pharyngeal arch, which gives rise to the glossopharyngeal nerve (CN IX), parts of the hyoid bone, and the stylopharyngeus muscle.

A 64-Year-Old Man Loses Consciousness near the Entrance to an Emergency