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,
Trabecular arteries Trabecular arteries The trabecular arteries are the name of the branches of the splenic artery after it passes into the trabeculae of the spleen, where it branches. When these arteries then reach the white pulp, and become covered with periarteriolar lymphoid sheaths, the name changes again to "central arteries" (or "central arterioles"). Branches of the central arteries are given to the red pulp, and these are called "penicillar arteries"). The lienal artery is remarkable for its large size in proportion to the size of the organ, and also for its tortuous course. It divides into six or more branches, which