See also: Carotid Body Paragangliomas; Carotid Body Tumor Case Example; Carotid Body Tumor Resection

Carotid Body

1. The carotid body is a chemoreceptor located in the adventitia of the bifurcation of the common carotid artery

2. Chemoreceptor function (Iturriaga et al. 2021)

   1. Carotid body monitors the blood’s pH, pCO2, and pO2 and thereby modulates cardiovascular and respiratory function primarily through sympathetic tone

   2. When the carotid body senses acidemia, hypercapnea, or hypoxia, autonomic firing leads to increased blood pressure, heart rate, and respiratory rate

   3. The function of the carotid body is complemented by other chemoreceptors, most notably the aortic body located in the aortic arch

3. Anatomy (Day et al. 2021)

   1. Located in the bifurcation of the common carotid artery

   2. Average size of carotid body is 3-5 mm in diameter and average weight is 12 mg

   3. Blood supply: from external carotid through Mayer’s ligament (provides attachment to carotids)

   4. Innervation: Hering’s nerve (aka carotid sinus nerve), a branch of the glossopharyngeal (CN IX), originating 1.5 cm distal to jugular foramen

4. Composed of two receptor cell types (Iturriaga et al. 2021):

   1. Chief cells (Type I): derived from neural crest, release ACh, ATP, dopamine in response to activation

   2. Sustentacular cells (Type II): supporting cells

Carotid Sinus

1. The carotid sinus is a baroreceptor that senses changes in systemic blood pressure and is located in the adventitia of the carotid bulb of the internal carotid artery

2. Due to its location, the carotid sinus is an intimately related but distinct organ from the carotid body

3. Innervation: same as carotid body (Hering’s nerve, aka carotid sinus nerve, a branch of CN IX)

4. The function of the carotid sinus can be affected by carotid body tumor resection

5. Carotid sinus syndrome (syncopal episodes due to inadvertant triggering of the carotid sinus) is a pathology of the carotid sinus; in addition, carotid massage triggers the carotid sinus pathway (increased pressure on carotid sinus due to massage → sends signal to decrease systemic BP) (Amin and Pavri 2015).

References

Iturriaga R, Alcayaga J, Chapleau MW, Somers VK. Carotid body chemoreceptors: physiology, pathology, and implications for health and disease. Physiol Rev. 2021 Jul 1;101(3):1177-1235. doi: 10.1152/physrev.00039.2019. Epub 2021 Feb 11. PMID: 33570461; PMCID: PMC8526340.

Day, Terry A. and Albergotti, W Greer: Neoplasms of the Neck Ch 115, 1755-1772.e3 in Cummings Otolaryngology: Head and Neck Surgery 7th Edition 2021 Elsevier, Inc.

Amin V, Pavri BB. Carotid sinus syndrome. Cardiol Rev. 2015 May-Jun;23(3):130-4. doi: 10.1097/CRD.0000000000000041. PMID: 25211534.

Netterville, James L., et al. "Carotid body tumors: a review of 30 patients with 46 tumors." The Laryngoscope 105.2 (1995): 115-126

Gray513.png: Henry Grayderivative work: Skoch3, Public domain, via Wikimedia Commons