ca·rot·id / kəˈrätid/ • adj. of, relating to, or denoting the two main arteries that carry blood to the head and neck, and their two main branches.• n. each of these arteries.ORIGIN: early 17th cent.: from French carotide or modern Latin carotides, from Greek karōtides, plural of karōtis ‘drowsiness,’ from karoun ‘stupefy’ (because compression of these arteries was thought to cause stupor).

carotid body One of a pair of tissue masses adjacent to the carotid sinus. Each contains receptors that are sensitive to oxygen and pH levels (acidity) in the blood. High levels of carbon dioxide in the blood lower the pH (i.e. increase the acidity). By responding to fluctuations in pH, the carotid body coordinates reflex changes in respiration rate. See also ventilation centre.

carotid (anat.) name of the two great arteries supplying blood to the head. XVII. — F. carotide or modL. carōtides — Gr. karōtídes, pl. of karōtís, f. karoûn stupefy; so named because compression of these arteries was said to produce stupor.

carotid body n. a small mass of tissue in the carotid sinus containing chemoreceptors that monitor levels of oxygen, carbon dioxide, and hydrogen ions in the blood.