The internal jugular vein is a major vein located in the neck that is responsible for draining deoxygenated blood from the brain, face, and neck. It runs parallel to the internal carotid artery and later the common carotid artery. It begins at the base of the skull in the jugular foramen and descends vertically within the carotid sheath, a fibrous structure that encloses it along with the carotid artery and vagus nerve. The internal jugular vein merges with the subclavian vein to form the brachiocephalic vein, which eventually drains into the superior vena cava, returning blood to the heart.
Location
The internal jugular vein is located deep within the neck, running vertically along the lateral side of the neck. It lies within the carotid sheath, a fibrous connective tissue that also contains the internal carotid artery (or common carotid artery) and the vagus nerve. The internal jugular vein extends from the base of the skull, starting in the jugular foramen, down to the level of the clavicle, where it joins the subclavian vein to form the brachiocephalic vein.
Anatomy
Origin
The internal jugular vein begins at the jugular foramen at the base of the skull. It arises as the continuation of the sigmoid sinus, a venous sinus that drains blood from the brain. As it emerges from the jugular foramen, the internal jugular vein descends in the neck, lying deep to the sternocleidomastoid muscle and lateral to the carotid artery.
Course
The internal jugular vein runs vertically down the neck, closely associated with the carotid artery. Initially, it lies lateral to the internal carotid artery, and as it descends, it becomes lateral to the common carotid artery. It remains enclosed within the carotid sheath for much of its course. The vein eventually passes behind the clavicle, where it joins with the subclavian vein to form the brachiocephalic vein.
Throughout its course, the internal jugular vein receives multiple tributaries from the face, neck, and brain.
Tributaries
The internal jugular vein receives several significant tributaries along its course:
- Facial Vein: Drains blood from the face and joins the internal jugular vein below the angle of the mandible.
- Lingual Vein: Drains the tongue and oral cavity.
- Pharyngeal Veins: Drain blood from the pharynx.
- Superior and Middle Thyroid Veins: Drain blood from the thyroid gland.
- Occipital Vein: May occasionally drain into the internal jugular vein, although it typically drains into the external jugular vein.
At the base of the neck, the internal jugular vein receives its largest tributary, the subclavian vein, which drains the upper limb.
Relations to Neighboring Structures
- Carotid Artery: The internal jugular vein runs lateral to the internal carotid artery in the upper neck and lateral to the common carotid artery in the lower neck. The close anatomical relationship between these vessels is important during surgical interventions.
- Vagus Nerve (CN X): The vagus nerve runs within the carotid sheath, positioned between the internal jugular vein and the carotid artery.
- Sternocleidomastoid Muscle: This muscle lies superficially to the internal jugular vein, providing protection from external forces. The vein runs deep to the sternocleidomastoid for most of its course.
- Jugular Bulb: At the upper portion of the internal jugular vein, near the jugular foramen, there is a dilation called the jugular bulb, which is involved in collecting venous blood from the brain via the sigmoid sinus.
Variations
The anatomy of the internal jugular vein can vary between individuals. In some cases, the size or course of the vein may differ, with occasional variations in the drainage patterns of its tributaries. The internal jugular vein is typically larger on the right side of the neck compared to the left, though this can vary. Some people may have accessory veins or duplications of the internal jugular vein.
Termination
The internal jugular vein terminates by merging with the subclavian vein at the root of the neck. This junction forms the brachiocephalic vein, which continues toward the thoracic cavity. The left and right brachiocephalic veins then join to form the superior vena cava, which delivers deoxygenated blood to the heart.
Function
Venous Drainage of the Brain
The primary function of the internal jugular vein is to drain deoxygenated blood from the brain. It begins as a continuation of the sigmoid sinus, one of the venous sinuses that collects blood from the cerebral veins. After collecting blood from the brain, the internal jugular vein transports it toward the heart for oxygenation. This role is critical for maintaining proper cerebral circulation and removing metabolic waste from the brain.
Drainage of the Neck and Face
In addition to the brain, the internal jugular vein is responsible for draining blood from various structures in the neck and face. Several tributaries, including the facial vein, lingual vein, and pharyngeal veins, converge into the internal jugular vein, collecting blood from the tongue, pharynx, and face. This ensures proper venous return from important areas such as the oral cavity, muscles, and tissues of the neck.
Drainage of the Thyroid Gland
The internal jugular vein also plays a significant role in draining blood from the thyroid gland. The superior and middle thyroid veins empty directly into the internal jugular vein. This ensures that deoxygenated blood from the thyroid gland, which is highly vascularized due to its role in hormone production, is efficiently transported back to the heart.
Maintenance of Cerebral Circulation
The internal jugular vein helps maintain appropriate cerebral circulation by ensuring that venous pressure within the brain remains within a healthy range. Proper venous drainage prevents the accumulation of excess blood or fluid within the brain, reducing the risk of increased intracranial pressure, which can lead to neurological issues. The internal jugular vein’s role in draining the brain is essential for maintaining normal brain function and preventing complications such as venous sinus thrombosis.
Transport of Deoxygenated Blood to the Heart
Ultimately, the internal jugular vein serves as a critical component of the systemic venous return pathway, transporting deoxygenated blood back to the heart. After receiving blood from the brain, face, neck, and thyroid, the internal jugular vein merges with the subclavian vein to form the brachiocephalic vein. The brachiocephalic veins from both sides of the body join to form the superior vena cava, which delivers blood to the right atrium of the heart, where it can be oxygenated by the lungs.
Support in Lymphatic Drainage
While its primary function is venous, the internal jugular vein indirectly assists in lymphatic drainage. It runs parallel to the deep cervical lymph nodes, which drain lymph from the head and neck. The internal jugular vein’s close association with the lymphatic system ensures proper fluid balance by facilitating the return of both blood and lymphatic fluid to the central circulatory system. The thoracic duct on the left side and the right lymphatic duct on the right side empty into the venous system near the junction of the internal jugular and subclavian veins.
Temperature Regulation
The internal jugular vein aids in regulating head and neck temperature by transporting heat-laden deoxygenated blood away from the brain and surrounding tissues. This function helps maintain a stable environment for the brain and other vital structures. Since the brain is highly sensitive to temperature changes, the efficient removal of heat through venous drainage is an important aspect of physiological homeostasis.
Clinical Significance
The internal jugular vein (IJV) plays a critical role in clinical practice due to its accessibility and function in venous drainage. It is frequently used for central venous catheterization, allowing direct access to the central venous system for medication administration, fluid management, or monitoring central venous pressure (CVP). The IJV’s relatively large size and straight course make it an ideal site for catheter insertion during emergency or intensive care situations.
The vein’s proximity to critical structures such as the carotid artery and vagus nerve makes procedures involving the IJV susceptible to complications, including arterial puncture, nerve damage, or hematoma formation. The IJV is also involved in conditions such as internal jugular vein thrombosis, which can lead to symptoms of venous congestion in the brain and face.
