Carotid Bodies

The carotid bodies are small, paired sensory organs located near the bifurcation of the common carotid arteries in the neck. They are the principal peripheral chemoreceptor organs for monitoring the chemical composition of arterial blood and contribute to the regulation of breathing and cardiovascular function. They respond particularly strongly when the partial pressure of oxygen in arterial blood falls, and they also respond to increased carbon dioxide and increased acidity .^1,2

The main sensory cells within each carotid body are type I cells, also called glomus cells. When these cells respond to relevant changes in blood gases, such as hypoxia, they become electrically activated and release neurotransmitters onto nearby sensory nerve endings. These signals travel to respiratory and autonomic control centers in the brainstem, where they can trigger reflex changes in ventilation and cardiovascular activity .^1,2

The carotid bodies are especially important for the ventilatory response to hypoxemia, meaning abnormally low arterial oxygen. Their activity increases as arterial oxygen falls, helping stimulate greater ventilation. They also participate in responses to hypercapnia and acidosis, allowing them to integrate several chemical signals related to respiratory and metabolic conditions .^1,2

The carotid body should not be confused with the carotid sinus. The carotid body is primarily a chemoreceptor organ that senses blood chemistry, whereas the carotid sinus contains baroreceptors that detect stretching of the arterial wall and contribute to regulation of blood pressure .¹