Internal carotid artery is known as the carotid sinus or the carotid bulb. The ascending portion of the cervical segment occurs distal to the bulb, when the vessel walls are again parallel. The internal carotid runs vertically upward in the carotid sheath and enters the skull through the carotid canal. During this part of its course, it lies in front of the transverse processes of the upper three cervical vertebrae. It is relatively superficial at its start, where it is contained in the carotid triangle of the neck, and lies behind and medial to the external carotid, overlapped by the sternocleidomastoid muscle, and
Carotid body sustentacular supportive cells. The carotid body contains the most vascularized tissue in the human body . The thyroid gland is very vascular, but not quite as much as the carotid body. The carotid body functions as a sensor: it responds to a stimulus, primarily O partial pressure, which is detected by the type I (glomus) cells, and triggers an action potential through the afferent fibers of the glossopharyngeal nerve, which relays the information to the central nervous system. The carotid body chemoreceptors are primarily sensitive to decreases in the partial pressure of oxygen (P). This is in contrast to the