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 body may involve mitochondrial oxygen sensors and the haem-containing cytochromes that undergo reversible one-electron reduction during oxidative-phosphorylation. Haem reversibly binds O with an affinity similar to that of the carotid body, suggesting that haem containing proteins may have a role in O, potentially this could be one of the complexes involved in oxidative-phosphorylation. This leads to increases in reactive oxygen species and rises in intracellular Ca. However, whether hypoxia leads to an increase or decrease in reactive oxygen species is unknown. The role of reactive oxygen species in hypoxia sensing is also under question. The oxygen dependent enzyme haem-oxidase has also