The jugular veins are a pair of major blood vessels in the neck that return deoxygenated blood from the entire head, including the brain, back toward the heart. These vessels act as the primary drainage route, ensuring that used blood can be cycled back for reoxygenation in the lungs. Without the continuous function of the jugular system, the brain would quickly suffer from a backup of blood.
The Dual Nature of the Jugular System
The jugular system is comprised of two distinct paired veins on each side of the neck: the Internal Jugular Vein (IJV) and the External Jugular Vein (EJV). These two veins differ significantly in their location and surrounding anatomy. The IJV is the larger of the two and follows a deep, protected path down the neck, beginning near the base of the skull.
It travels within a protective sleeve of connective tissue called the carotid sheath, where it runs directly alongside the common carotid artery and the vagus nerve. This deep location means the IJV is generally not visible or easily felt, as it is covered by the large, strap-like sternocleidomastoid muscle. Its course is straight, descending to the base of the neck where it merges with the subclavian vein to form the brachiocephalic vein.
The EJV, in contrast, is smaller and takes a much more superficial route, making it easily visible in some people, particularly when straining. This vein is positioned just beneath the skin, running diagonally across the surface of the sternocleidomastoid muscle before descending toward the clavicle. Due to its shallow location, the EJV is more susceptible to injury.
Essential Role in Circulation
The function of the jugular veins is to provide the main pathway for venous outflow from the head and neck, delivering blood to the superior vena cava for return to the heart. The IJV is responsible for draining the vast majority of blood from the brain itself.
This blood is collected from the brain’s specialized drainage channels, the dural venous sinuses, before exiting the skull and entering the IJV. The large capacity of the IJV is necessary to manage the continuous, high-volume blood flow required by the brain. The EJV, conversely, drains blood from the superficial structures of the head and face, including the scalp and some areas of the face.
Once the blood is collected, both jugular veins eventually converge with the subclavian vein at the base of the neck. This junction forms the brachiocephalic vein, which then unites with its counterpart to create the superior vena cava, the large vessel that empties directly into the heart’s right atrium. This streamlined path ensures that used blood is efficiently transported for reoxygenation.
Clinical Relevance and Vulnerability
The IJV’s deep, stable position and direct path to the heart make it a preferred site for the placement of a Central Venous Catheter (CVC). This procedure, often guided by ultrasound, allows medical professionals to administer medications, fluids, or nutrition directly into the bloodstream or to monitor central venous pressures.
The EJV, due to its superficial location, is often used by doctors to visually assess a patient’s fluid status and heart health by observing the Jugular Venous Pressure (JVP). When pressure in the right side of the heart is elevated, such as in cases of heart failure, the EJV may become distended in the neck. Measuring the height of this pulsation provides a non-invasive estimate of the pressure within the central veins.
The jugular veins are vulnerable to injury, particularly in cases of severe neck trauma. The superficial EJV is at greater risk of laceration due to its proximity to the skin surface. A unique danger associated with trauma or medical procedures involving either jugular vein is the risk of venous air embolism.
Because the pressure inside these large veins is often lower than the surrounding atmospheric pressure, a puncture can cause air to be sucked directly into the bloodstream. This air can travel quickly to the heart and lungs, potentially leading to a life-threatening blockage of blood flow. This complication mandates careful technique during any procedure involving the jugular veins.