Inferior laryngeal vein

The inferior laryngeal vein is a vein located in the larynx, specifically around the lower part of the laryngeal structure. It drains venous blood from the inferior portion of the larynx, which includes the vocal cords and surrounding tissues.^[1] The inferior laryngeal vein accompanies the inferior laryngeal artery and courses downward to drain into the inferior thyroid vein. The blood from the inferior thyroid vein then flows into larger veins, such as the brachiocephalic vein, eventually reaching the superior vena cava. This vein is part of the vascular system that serves the larynx and its adjacent structures.

Location

The inferior laryngeal vein is located within the larynx, primarily in the lower portion of the laryngeal structure. It is closely associated with the vocal cords, the surrounding muscles, and the connective tissues of the larynx. The vein runs alongside the inferior laryngeal artery, which supplies the same region, and courses downward into the neck.

Anatomy

Origin

The inferior laryngeal vein originates from the venous plexus within the lower part of the larynx. This venous plexus collects deoxygenated blood from the structures of the lower larynx, including the vocal cords, cricoid cartilage, and intrinsic laryngeal muscles. The venous blood is then collected into the inferior laryngeal vein.

Course

The inferior laryngeal vein follows the course of the inferior laryngeal artery, which is a branch of the inferior thyroid artery.^[7] The vein runs downwards, exiting the larynx and continuing along the side of the thyroid gland. As it descends, it follows a similar path as the inferior laryngeal nerve, which supplies the intrinsic muscles of the larynx. The vein eventually converges with the inferior thyroid vein, which drains blood from the thyroid gland and the surrounding areas. This convergence typically occurs at the lower border of the thyroid gland.

Termination

The inferior laryngeal vein terminates by draining into the inferior thyroid vein. The inferior thyroid vein then empties into the brachiocephalic vein, which carries deoxygenated blood toward the superior vena cava.^[4] The superior vena cava, in turn, returns the blood to the heart for oxygenation.

Relations to Neighboring Structures

• Inferior Laryngeal Artery: The inferior laryngeal vein runs parallel to the inferior laryngeal artery, which is a branch of the inferior thyroid artery. Both the vein and the artery supply and drain the lower laryngeal structures.
• Inferior Laryngeal Nerve: The vein is also closely related to the inferior laryngeal nerve, a branch of the recurrent laryngeal nerve. This nerve runs alongside the vein and innervates the intrinsic muscles of the larynx, which control vocal cord movement.
• Thyroid Gland: The inferior laryngeal vein runs adjacent to the thyroid gland, and it drains into the inferior thyroid vein, which collects blood from the thyroid gland as well.
• Trachea: As the vein descends, it is located near the trachea, which is positioned anterior to the larynx and provides structural support to the airway.

Tributaries

The inferior laryngeal vein receives blood from smaller tributaries within the lower larynx, including:

• Venous Plexuses of the Larynx: These are networks of small veins that drain the vocal cords, intrinsic laryngeal muscles, and connective tissue of the lower larynx.
• Subglottic Region: The region below the vocal cords also contributes to the venous return via smaller veins that join the inferior laryngeal vein.

Variations

The anatomy of the inferior laryngeal vein can show slight variations between individuals.^[5] While it typically drains into the inferior thyroid vein, there may be minor differences in the exact course or size of the vein, as well as its connections to nearby venous structures.^[6] In some cases, additional venous branches may join the inferior laryngeal vein, providing more extensive drainage of the lower larynx and adjacent tissues.

Function

Venous Drainage of the Lower Larynx

The primary function of the inferior laryngeal vein is to drain deoxygenated blood from the lower portion of the larynx, which includes structures such as the vocal cords, cricoid cartilage, and surrounding connective tissues. The larynx plays a key role in voice production and breathing, and the inferior laryngeal vein helps maintain proper circulation in this region by removing blood that has delivered oxygen and nutrients to these tissues.

Drainage of the Vocal Cords

The vocal cords, located in the lower part of the larynx, are highly vascularized due to their constant activity in speech and respiration. The inferior laryngeal vein is responsible for draining venous blood from the vocal cords after oxygen exchange has occurred. Efficient drainage is crucial for preventing venous congestion and ensuring the vocal cords function optimally, especially during periods of intense vocal activity.

Drainage of the Intrinsic Muscles of the Larynx

The inferior laryngeal vein also drains venous blood from the intrinsic muscles of the larynx, which are responsible for controlling the tension and position of the vocal cords. These muscles, including the thyroarytenoid, cricothyroid, and posterior cricoarytenoid muscles, play a critical role in adjusting the pitch and volume of the voice. The vein ensures that deoxygenated blood is efficiently removed from these active muscles, maintaining their function during vocalization and respiration.^[8]

Removal of Metabolic Waste Products

Like other veins, the inferior laryngeal vein is involved in the removal of metabolic waste products from the tissues it drains. The larynx, particularly the vocal cords and muscles, generates metabolic byproducts during regular activity, such as carbon dioxide and lactic acid.^[3] The inferior laryngeal vein transports these waste products away from the laryngeal tissues, allowing for their removal from the bloodstream and preventing a buildup that could impair tissue function.

Drainage of the Subglottic Region

The inferior laryngeal vein helps drain the subglottic region, which lies below the vocal cords and serves as an important part of the airway. This region, rich in connective tissues and small glands, contributes to the overall function of the larynx in respiration and phonation. The inferior laryngeal vein ensures that blood from the subglottic area is returned to the systemic venous circulation, helping to maintain a healthy and functional lower airway.

Connection to the Systemic Venous Circulation

The inferior laryngeal vein is an important part of the systemic venous circulation, as it drains into the inferior thyroid vein, which then connects to the larger venous system. This pathway ensures that deoxygenated blood from the larynx is efficiently returned to the heart. By connecting the venous drainage of the larynx to the brachiocephalic vein and eventually the superior vena cava, the inferior laryngeal vein plays a role in maintaining the overall circulation of the neck and thorax.

Prevention of Venous Congestion in the Larynx

By providing a direct route for venous blood to leave the lower larynx, the inferior laryngeal vein helps prevent venous congestion in the laryngeal tissues.^[2] Congestion in the vocal cords, muscles, or subglottic region could lead to swelling or impaired vocal function. The inferior laryngeal vein prevents this by ensuring that blood is regularly and efficiently drained, maintaining proper tissue health and function.

Support for Voice Production and Respiration

The drainage provided by the inferior laryngeal vein indirectly supports the function of the larynx in voice production and respiration. By removing deoxygenated blood from the vocal cords and laryngeal muscles, the vein helps these tissues maintain the oxygenation and nutrient supply they need to function during speech and breathing. Efficient drainage is especially important during activities that require prolonged vocalization, such as speaking or singing, as it ensures that the vocal cords remain healthy and capable of continuous movement.

Assistance in Regulation of Laryngeal Blood Flow

The inferior laryngeal vein contributes to the regulation of blood flow in the larynx, balancing the incoming oxygenated blood from the inferior laryngeal artery with the outflow of deoxygenated blood. This balance is essential for the proper functioning of the larynx, especially during activities that place higher demands on the vocal cords, such as singing, shouting, or sustained phonation.

Clinical Significance

The inferior laryngeal vein is clinically significant due to its role in draining blood from the vocal cords and lower larynx.^[1] During surgical procedures involving the larynx or thyroid gland, such as thyroidectomy or laryngectomy, the vein may be at risk of injury, leading to bleeding or hematoma formation. Its close association with the inferior laryngeal nerve also raises the risk of nerve injury, potentially causing vocal cord paralysis or hoarseness if damaged. In conditions like laryngeal inflammation or tumors, the inferior laryngeal vein may become engorged or obstructed, affecting venous drainage and contributing to symptoms such as swelling or impaired vocal function. Additionally, disorders that cause venous congestion in the neck can impact the venous return through the inferior laryngeal vein, leading to further complications in the laryngeal region.