Where is the carotid body located?

The Carotid Body: Location and Function

The carotid body is located in the adventitia of the common carotid artery bifurcation and functions as a chemoreceptor, not a pressure receptor or osmoreceptor. 1, 2

Anatomical Location

• The carotid body is bilaterally located between the external and internal carotid arteries at the carotid bifurcation 2
• It is specifically found in the adventitia (outer layer) of the common carotid artery at its bifurcation 1
• The carotid body is not located in the media or subintimal layers of the artery 1
• It is typically found at the level of the thyroid cartilage (Adam's apple) in the groove between the trachea and sternocleidomastoid muscle 3

Structure of the Carotid Body

• The carotid body is composed of highly perfused cell clusters, or glomeruli, that are innervated by sensory fibers 4
• Glomus cells (also called chief cells) are the most abundant cells in each glomerulus and serve as the primary sensory elements 4, 5
• The carotid body has a complex neural structure with connections to both respiratory and cardiovascular control pathways 5
• The sensory nerve endings of the carotid sinus nerve penetrate the cell clusters to form synapses with the chemoreceptor cells 6

Function of the Carotid Body

• The carotid body functions primarily as a chemoreceptor that detects changes in the chemical composition of blood 2, 4
• It is specifically designed to detect and respond to changes in:
  • Oxygen tension (hypoxia) 4
  • Carbon dioxide levels and pH (hypercapnia and acidosis) 4
  • Other parameters including glucose and lactate levels 4
• When stimulated (e.g., during hypoxia), the carotid body activates afferent nerve fibers that signal the brainstem to initiate compensatory responses such as hyperventilation and sympathetic activation 4
• This makes it essential for cardiorespiratory homeostasis, particularly in the reflex adjustment of respiration according to arterial blood gas values 5

Clinical Significance

• Carotid body tumors (chemodectomas) can develop as rare neoplasms arising from this structure 1
• These tumors typically present as gradually enlarging, non-tender anterolateral neck masses 1
• When examining the carotid artery, the American Heart Association recommends positioning the patient in a supine position with the neck slightly extended 3
• The head should be turned approximately 45° toward the side opposite to the one being examined to facilitate proper assessment 3

Historical Context

• The carotid body was first reported by Von Haller and Taube in the mid-18th century, but detailed study began in the early 20th century 2
• Fernando De Castro first described the carotid body as a sensory receptor (chemoreceptor) between 1926 and 1929, marking the first description of arterial chemoreceptors 2
• Corneille Heymans later provided physiological demonstration of De Castro's hypothesis regarding chemoreceptors, work for which he was awarded the Nobel Prize in Physiology or Medicine in 1938 2