Carotid sheath sternum. The four major structures contained in the carotid sheath are: The carotid artery lies medial to the internal jugular vein, and the vagus nerve is situated posteriorly between the two vessels. In the upper part, the carotid sheath also contains the glossopharyngeal nerve (IX), the accessory nerve (XI), and the hypoglossal nerve (XII), which pierce the fascia of the carotid sheath. The ansa cervicalis is embedded in the anterior wall of sheath. It is formed by "descendens hypoglossi" (C1) and "descendens cervicalis" (C2-C3). The three major fascial layers in the neck contribute to the carotid sheath: the investing fascia,
Carotid triangle still more inferiorly, the external branch of the same nerve. The upper portion of the larynx and lower portion of the pharynx are also found in the front part of this space. Carotid triangle The carotid triangle (or superior carotid triangle) is a portion of the anterior triangle of the neck. It is bounded: It is (covered) by the integument, superficial fascia, Platysma and deep fascia; Its floor is formed by parts of the -1 Thyrohyoid membrane, -2Hyoglossus, and the -3Constrictores pharyngis medius and inferior. The external and internal carotids lie side by side, the external being the more anterior