sinuscarotidis

Sinus caroticidis, commonly referred to in English as the carotid sinus, is the dilated proximal portion of the internal carotid artery just above its origin from the common carotid artery. It is distinct from the carotid body, a separate chemoreceptor located near the same region. The carotid sinus serves as a baroreceptor area that helps regulate blood pressure by detecting stretch of the arterial wall.

Structure and innervation

The carotid sinus contains mechanosensitive nerve endings that respond to changes in arterial wall tension. Sensory information from the sinus is conveyed predominantly by the glossopharyngeal nerve (the Hering’s nerve) to the nucleus tractus solitarius in the brainstem. Efferent autonomic pathways then adjust heart rate, contractility, and vascular tone to stabilize blood pressure.

Physiological role

Through the carotid sinus reflex, increases in blood pressure cause a reflex decrease in heart rate and peripheral vasodilation, while decreases in pressure trigger the opposite response. This reflex contributes to short-term regulation of blood pressure during postural changes and other physiological maneuvers.

Clinical relevance

Carotid sinus massage, which stimulates the sinus to induce a parasympathetic response, can be used diagnostically or therapeutically for certain supraventricular tachycardias. It is contraindicated in patients with known carotid artery disease, significant carotid stenosis, or recent cerebrovascular events such as stroke or transient ischemic attack, and should be performed with caution under medical supervision.

Variations and imaging

The size and prominence of the carotid sinus vary among individuals. The region can be evaluated noninvasively with ultrasound or other vascular imaging modalities when clinical assessment is inconclusive or when vascular pathology is suspected.