The occipital artery is one of the posterior branches of the external carotid artery and is primarily responsible for supplying blood to the posterior scalp, parts of the neck, and the muscles in the upper cervical region. It is an important artery in the vascular network of the head and neck.
Location
The occipital artery originates from the external carotid artery, usually at the same level as the facial artery, just below the posterior belly of the digastric muscle. From its origin, it courses upward and posteriorly, running beneath the digastric muscle and the sternocleidomastoid muscle. It ascends toward the back of the head, passing through the occipital region and traveling along the base of the skull, where it supplies the scalp and the posterior muscles of the neck. The artery also forms anastomoses with other arteries in the scalp and neck region, such as the superficial temporal and posterior auricular arteries.
Structure and Anatomy
Origin
The occipital artery arises from the external carotid artery, typically at the level of the hyoid bone and opposite the facial artery. Its origin is near the posterior aspect of the neck, just below the posterior belly of the digastric muscle. It is one of the posterior branches of the external carotid artery, along with the posterior auricular artery.
Course
After its origin, the occipital artery travels posteriorly and upward. Initially, it runs deep to the posterior belly of the digastric muscle and the stylohyoid muscle, passing beneath them. The artery then emerges posterior to the mastoid process, where it becomes more superficial. As it ascends, the occipital artery passes over the transverse process of the atlas (the first cervical vertebra) and continues along the posterior aspect of the skull.
The artery crosses the inferior aspect of the sternocleidomastoid muscle, supplying this region and giving off muscular branches. As it ascends further, it continues toward the posterior scalp, running along the back of the head in the occipital region.
Branches
The occipital artery gives off several important branches during its course, which supply different regions of the scalp, neck, and muscles:
- Sternocleidomastoid Branches: These branches supply the sternocleidomastoid muscle and nearby muscles in the neck. The artery often provides two or more branches to this muscle.
- Auricular Branches: These small branches supply the posterior aspect of the external ear, particularly the skin and connective tissues behind the auricle.
- Descending Branch: This is one of the largest branches of the occipital artery. It descends into the neck, supplying muscles such as the trapezius, splenius capitis, and semispinalis capitis. The descending branch also contributes to anastomoses with other cervical arteries, such as the deep cervical artery and the vertebral artery.
- Meningeal Branches: Small branches from the occipital artery supply the dura mater (the outermost layer of the meninges) of the posterior cranial fossa.
- Muscular Branches: In addition to the sternocleidomastoid branches, the occipital artery gives off muscular branches that supply the deep muscles of the back of the neck, such as the trapezius and splenius muscles.
Termination
The occipital artery continues toward the posterior aspect of the scalp, where it divides into several terminal branches. These branches supply the skin, connective tissues, and muscles in the occipital region of the scalp. The terminal branches anastomose with the posterior auricular artery and branches of the superficial temporal artery, forming a rich vascular network in the scalp.
Anastomoses
The occipital artery forms important anastomotic connections with other arteries in the head and neck region. Some of the key anastomoses include:
- Posterior Auricular Artery: The occipital artery anastomoses with the posterior auricular artery, which also supplies the posterior aspect of the ear and the scalp behind the ear.
- Superficial Temporal Artery: Terminal branches of the occipital artery anastomose with branches of the superficial temporal artery, ensuring continuous blood supply to the scalp, even if one of the arteries is compromised.
- Vertebral and Deep Cervical Arteries: The descending branch of the occipital artery forms anastomoses with the vertebral artery and the deep cervical artery, contributing to collateral circulation in the upper cervical region.
Surrounding Structures
As it travels toward the occipital region, the occipital artery is in close relation to several key anatomical structures:
- Sternocleidomastoid Muscle: The artery gives off branches to this muscle as it passes over its inferior portion.
- Mastoid Process: The artery passes posterior to the mastoid process of the temporal bone.
- Auricle (External Ear): Small auricular branches extend toward the posterior aspect of the external ear.
- Cervical Muscles: The artery supplies numerous muscles in the neck, including the trapezius, splenius, and semispinalis capitis.
Path to the Scalp
Upon reaching the posterior scalp, the occipital artery continues to run superficially, distributing blood to the scalp tissue and forming an extensive network with other arteries supplying this region. It lies within the subcutaneous layer of the scalp, just deep to the skin, making it accessible in procedures such as scalp surgeries. The artery’s superficial course allows it to be easily palpated in the occipital region.
Function
Blood Supply to the Posterior Scalp
One of the primary functions of the occipital artery is to provide blood to the posterior scalp. As it ascends toward the back of the head, the artery delivers oxygenated blood to the skin, subcutaneous tissues, and hair follicles in the occipital region. This ensures proper nourishment for the scalp, contributing to the health and maintenance of the skin and hair. The occipital artery’s terminal branches form a rich vascular network, which is essential for scalp tissue regeneration and repair.
Vascularization of the Sternocleidomastoid Muscle
The occipital artery supplies blood to the sternocleidomastoid muscle through its sternocleidomastoid branches. This muscle plays a critical role in head movement, including rotation and flexion of the neck. Adequate blood flow from the occipital artery ensures that the muscle receives the oxygen and nutrients it needs for proper function, especially during head and neck movements.
Blood Supply to the Deep Neck and Upper Cervical Muscles
The occipital artery plays a crucial role in supplying the deep muscles of the upper neck and cervical region. These muscles include the trapezius, splenius capitis, and semispinalis capitis. The artery’s descending branch is particularly important for providing oxygenated blood to these muscles. These muscles are essential for head movement, posture, and stabilization, and their function depends on a constant supply of blood to support their activity.
Nourishment of the Posterior Auricular Region
The occipital artery provides blood to the skin and connective tissues of the posterior aspect of the ear (auricle) through its auricular branches. This ensures that the skin and soft tissues in the area remain healthy and well-nourished, contributing to the structural integrity and function of the external ear.
Contribution to Collateral Circulation
One of the vital functions of the occipital artery is its contribution to collateral circulation in the head and neck region. It forms anastomoses with the posterior auricular, vertebral, deep cervical, and superficial temporal arteries, ensuring a robust vascular network. Collateral circulation is crucial for maintaining blood flow in the event of an arterial blockage or damage to one of the vessels. This network helps prevent ischemia and ensures that tissues continue to receive an adequate blood supply even when primary arteries are compromised.
Supply to the Dura Mater
Through its meningeal branches, the occipital artery provides blood to the dura mater, the outermost protective covering of the brain and spinal cord. These small branches ensure that the dura mater in the posterior cranial fossa receives the necessary blood flow for maintaining its protective and supportive functions.
Nutrient Delivery to the Trapezius Muscle
The occipital artery supplies blood to the trapezius muscle, a large muscle responsible for moving, stabilizing, and rotating the scapula (shoulder blade). By delivering oxygen and nutrients through its muscular branches, the occipital artery ensures that the trapezius muscle can perform its vital functions, particularly in activities that involve raising or lowering the shoulders, or extending the neck.
Support for Healing and Tissue Repair
Like all arteries, the occipital artery provides essential nutrients, including oxygen, to the tissues it supplies. This function is vital for maintaining the health of the scalp, muscles, and other structures in the occipital and cervical regions. The artery plays a key role in tissue repair and regeneration, especially in cases of injury, surgery, or trauma to the scalp, neck, or upper back. A healthy blood supply supports wound healing and reduces the risk of complications.
Role in Thermoregulation of the Scalp
By regulating blood flow to the posterior scalp, the occipital artery also contributes to thermoregulation. Increased blood flow to the scalp allows the body to dissipate excess heat through the skin, while reduced flow helps conserve heat. This process is important in maintaining overall body temperature, especially in environments where the head and scalp are exposed to temperature changes.
Clinical Significance
The occipital artery holds significant clinical relevance due to its role in supplying blood to the scalp, neck muscles, and dura mater. It is frequently involved in various medical and surgical contexts.
Occipital Neuralgia
The occipital artery is closely associated with the greater occipital nerve. Compression or irritation of the artery can contribute to occipital neuralgia, a condition characterized by chronic headaches or sharp, stabbing pain in the back of the head. Treatments may include nerve blocks or, in some cases, surgical decompression of the artery and nerve.
Scalp and Neck Surgery
During scalp surgeries or procedures in the occipital region, such as hair transplants or removal of lesions, the occipital artery’s location and branches are important to avoid excessive bleeding. Surgeons must be cautious to preserve the artery or control bleeding if it is inadvertently damaged.
Vascular Surgery and Grafting
The occipital artery can be used in microvascular surgeries or grafting procedures due to its accessibility. It may also serve as a collateral source of blood supply during surgeries on other arteries in the head and neck, especially in cases where alternative arteries are blocked.
Head and Neck Trauma
Due to its superficial course in the posterior scalp, the occipital artery is susceptible to injury in cases of trauma to the back of the head. Trauma can result in significant bleeding, requiring careful management in emergency situations or surgical settings.
