The internal jugular vein combines with the subclavian vein to form the brachiocephalic vein, which carries blood to the right atrium. Since there aren't any valves in the brachiocephalic vein, the pulsation of the internal jugular vein can help in giving a fairly accurate estimate of the right atrial pressure.
Veins are an integral component of the circulatory system of the human body. With the exception of the pulmonary vein, all the veins perform the function of transporting deoxygenated blood to the heart. The venous system of the head and neck include several veins such as internal and external jugular veins, vertebral veins, facial vein, occipital vein, superficial temporal vein, posterior auricular vein, brachiocephalic vein, subclavian vein, superior vena cava, etc.
The jugular veins play an important role in the venous drainage of the head and the neck. Located besides the common carotid artery in the neck, the internal jugular veins are primarily responsible for carrying deoxygenated blood from the brain, as well as superficial parts of the face and the neck to the heart. The internal jugular veins lie deeper and are larger than the external jugular veins, which lie closer to the surface.
Internal Jugular Vein Anatomy and Function
Inferior petrosal and sigmoid dural venous sinuses, which are venous channels located between the layers of the dura mater (the outermost membrane that envelops the brain and the spinal cord), unite to form the internal jugular veins. The internal jugular vein emerges from the posterior of a large aperture called jugular foramen, which is located at the base of the skull. It is continuous with the transverse sinus, which is a dural venous sinus. It is dilated at two places, which are referred to as the superior bulb and the inferior bulb. The superior bulb is located at its origin, whereas the inferior bulb is located around the place where the vein terminates.
In the neck, this vein runs down, deep to the sternocleidomastoid muscle, which runs from the sternum and the collarbone to the mastoid and occipital bone. It rests beside the thyroid gland. At first, it lies lateral to the internal carotid artery, and then lateral to the common carotid artery. The internal jugular veins are paired veins that are placed laterally to the carotid artery on either side of the neck. While the left internal jugular vein is closer to the carotid artery to the extent that it overlaps, there is some distance between the right internal jugular vein and the common carotid artery. The right vein is slightly larger than the left.
As the vein runs down the neck, it also receives blood from other veins such as the facial vein, lingual veins, occipital vein, pharyngeal veins, superior and the middle thyroid veins. Running posteriorly to the sternal end of the collarbone, it combines with the subclavian vein behind the medial end of the collarbone at the bottom of the neck to form the brachiocephalic vein (also called innominate vein). From here, the blood first flows into the superior vena cava, from where it flows into the right atrium of the heart. The vein dilates just before the site of termination. This place of dilation at the inferior end is referred to as the inferior bulb. Like all veins, the internal jugular vein contains a pair of valves to prevent the blood from flowing back. This valve is located at the inferior bulb, placed around 2 centimeters above the termination of the vein. The following internal jugular vein diagram shows the location of its tributaries and other veins of the head and the neck.
External and Anterior Jugular Veins
While the internal jugular veins carry deoxygenated blood from the brain and the superficial parts of the face, the external jugular vein drains the outer structures of the head (scalp) and the deep sections of the face. Two veins combine at the angle of the mandible to form the external jugular. These are posterior auricular vein and anterior branch of the retromandibular vein. While the former returns deoxygenated blood from the part of the scalp that lies above and behind the outer ear, the latter is formed by the maxillary and superficial temporal veins, which are responsible for the venous drainage of the face.
After formation, the external jugular vein runs down anteriorly to the sternocleidomastoid muscle. At the bottom of the neck, it passes underneath the collarbone, thereby draining into the subclavian vein. The external jugular receives deoxygenated blood from the deep tissues of the face and the exterior of the cranium, which is the part of the skull that encloses the brain. The external jugular drains into the subclavian vein. Its tributaries include:
Posterior external jugular vein
Anterior jugular vein
While the posterior external jugular vein receives blood from the back of the neck, the anterior jugular veins receive blood from the voice box and tissues that lie below the lower jaw. The anterior jugular is a paired tributary of the external jugular vein that originates around the hyoid bone and runs down around the midline of the neck. They drain the anterior aspect of the neck and empty into the subclavian vein.
On a concluding note, the jugular veins are an integral component of the venous system of the head and the neck. Due to its location and large size, the internal jugular vein is often used for the placement of venous lines for the administration of fluids or measurement of the jugular venous pressure. The jugular venous pressure reading can provide valuable insights on the blood circulation in the right side of the heart, which in turn can help in the diagnosis of right-sided heart failure.