Supratrochlear artery

The supratrochlear artery, also known as the frontal artery, is a small branch of the ophthalmic artery that supplies blood to the forehead and scalp. It is one of the terminal branches of the ophthalmic artery, along with the supra-orbital artery.

Location

The supratrochlear artery originates from the ophthalmic artery in the orbit and ascends toward the forehead. It passes superior to the trochlea (a pulley-like structure for the superior oblique muscle of the eye) and exits the orbit through the supraorbital notch or foramen. From here, the artery ascends on the forehead, running near the midline, and continues to supply the skin, subcutaneous tissue, and muscles of the forehead and scalp. It travels alongside the supratrochlear nerve and forms anastomoses with other arteries in the forehead, such as the supra-orbital artery and branches of the superficial temporal artery.

Anatomy

The supratrochlear artery, also known as the frontal artery, is a terminal branch of the ophthalmic artery that plays a key role in supplying blood to the forehead and scalp. Its anatomical course and relationships are essential for understanding its role in vascularizing the upper facial structures. Below is a detailed description of the anatomy of the supratrochlear artery.

Origin

The supratrochlear artery originates from the ophthalmic artery, a branch of the internal carotid artery, within the orbit. It typically arises as one of the terminal branches of the ophthalmic artery along with the supra-orbital artery. Both these arteries are responsible for supplying the upper facial regions, but the supratrochlear artery is smaller and more medial in its course.

Course

• Intraorbital Segment: After originating from the ophthalmic artery within the orbit, the supratrochlear artery runs anteriorly and medially within the orbit, superior to the medial rectus muscle and close to the trochlea (the pulley-like structure for the superior oblique muscle). The artery is named “supratrochlear” because it passes superior to the trochlea as it travels toward the forehead.
• Exit Through the Supraorbital Notch/Foramen: The supratrochlear artery exits the orbit by passing through the supraorbital notch or foramen, a small bony opening located in the superior orbital margin. In most cases, the artery emerges slightly medial to the supraorbital artery, which exits through the same region. After exiting the orbit, the artery travels toward the forehead, running in close proximity to the supratrochlear nerve.
• Forehead Segment: Once the artery exits the orbit, it ascends on the forehead, running just lateral to the midline of the forehead. It passes deep to the frontalis muscle, providing blood to the skin, muscles, and soft tissues of the forehead and scalp. The artery continues upward and runs along the medial aspect of the forehead, supplying its structures as it ascends toward the scalp.

Branches of the Supratrochlear Artery

• Muscular Branches: As it ascends, the supratrochlear artery gives off small branches that supply the frontalis muscle. This muscle is responsible for facial expressions involving the forehead, such as raising the eyebrows and wrinkling the forehead. The artery ensures that the frontalis muscle receives adequate blood flow for its function.
• Cutaneous Branches: The supratrochlear artery provides cutaneous branches that supply the skin of the forehead. These branches play a role in maintaining the skin’s health by delivering oxygenated blood to the upper layers of the skin, contributing to its overall nourishment and healing capacity.
• Anastomotic Branches: The supratrochlear artery forms anastomoses (connections) with other arteries supplying the scalp and forehead. It anastomoses with the supra-orbital artery, which is its counterpart on the lateral side of the forehead. Additionally, it connects with branches of the superficial temporal artery, a terminal branch of the external carotid artery. These anastomoses help create a rich vascular network that ensures collateral circulation in the event of arterial blockages or injuries.
• Dorsal Nasal Branches: The supratrochlear artery often gives rise to small dorsal nasal branches that descend toward the nose. These branches supply blood to the upper part of the nasal bridge, providing vascularization to the soft tissues and skin in this region.

Anatomical Relations

• Trochlea and Superior Oblique Muscle: The supratrochlear artery runs superior to the trochlea, a fibrous loop through which the tendon of the superior oblique muscle passes. The proximity to this structure gives the artery its name, as it runs just above this pulley-like system for the superior oblique muscle.
• Medial Rectus Muscle: The artery lies superior to the medial rectus muscle during its intraorbital course. The medial rectus is one of the extraocular muscles responsible for moving the eye medially (toward the nose), but the artery does not supply this muscle directly.
• Supratrochlear Nerve: The supratrochlear artery runs in close proximity to the supratrochlear nerve, which is a branch of the frontal nerve, itself a division of the ophthalmic branch of the trigeminal nerve. This nerve provides sensory innervation to the forehead and scalp, and the artery often travels alongside it. The proximity of the artery and nerve allows for coordinated vascular and sensory supply to the same region.
• Supra-orbital Artery: The supratrochlear artery runs medial to the supra-orbital artery, which is another terminal branch of the ophthalmic artery. While both arteries supply the forehead and scalp, the supratrochlear artery typically supplies the more medial portion of the forehead, while the supra-orbital artery supplies the lateral portion.

Anastomoses

• Anastomosis with Supra-orbital Artery: The supratrochlear artery anastomoses with the supra-orbital artery, creating a vascular network that supplies the forehead and scalp. This connection ensures that blood flow to the forehead remains constant, even if one artery becomes obstructed.
• Anastomosis with Superficial Temporal Artery: As the artery ascends to the scalp, it forms anastomoses with branches of the superficial temporal artery, which is a terminal branch of the external carotid artery. This connection creates an additional source of blood flow to the forehead and scalp, ensuring sufficient vascular supply to the upper facial and cranial structures.
• Anastomosis with Dorsal Nasal Artery: The supratrochlear artery may also form anastomoses with the dorsal nasal artery, another branch of the ophthalmic artery that supplies the nasal bridge and surrounding areas. This connection helps maintain vascular supply to the nose and upper facial region.

Termination

The supratrochlear artery terminates as it ascends toward the scalp, providing branches to the skin, subcutaneous tissues, and muscles of the forehead and scalp. Its anastomoses with the supra-orbital and superficial temporal arteries ensure that blood flow to the upper face and scalp remains adequate, even in cases of local arterial compromise.

Function

The supratrochlear artery plays a crucial role in supplying blood to the forehead, scalp, and surrounding facial structures. Below is a detailed explanation of the various functions of the supratrochlear artery, highlighting the specific areas it serves and how it supports their physiological needs.

Blood Supply to the Forehead

Nourishment of the Skin

One of the primary functions of the supratrochlear artery is to supply blood to the skin of the forehead. This ensures the skin remains healthy, receives enough oxygen, and maintains its structural integrity. The artery’s blood supply also supports the skin’s ability to heal from minor injuries and to maintain its elasticity and vitality.

Perfusion of Subcutaneous Tissues

Beneath the skin, the supratrochlear artery supplies the subcutaneous tissues of the forehead. These tissues include fat and connective tissue layers, which require a steady blood flow to remain functional. The artery ensures that these tissues are well-oxygenated and nourished, supporting their role in providing structure and protection to the forehead.

Blood Supply to the Frontalis Muscle

Vascularization of the Frontalis Muscle

• The frontalis muscle is a key muscle in the forehead, responsible for facial expressions like raising the eyebrows and wrinkling the forehead. The supratrochlear artery provides oxygen-rich blood to this muscle, ensuring that it functions efficiently in expressing emotions and controlling movements of the forehead.
• The artery supports muscle health by delivering nutrients and oxygen, allowing for proper contraction and relaxation of the frontalis muscle. Without adequate blood supply, the muscle’s function would be impaired, affecting facial expressions.

Blood Supply to the Scalp

Perfusion of the Scalp

• The supratrochlear artery ascends from the forehead to the scalp, providing blood to the skin, subcutaneous tissue, and other structures. The scalp requires a robust blood supply to maintain its health, especially considering its role in protecting the skull and supporting hair growth.
• The artery helps nourish the scalp tissues, ensuring that the skin remains healthy and capable of sustaining hair follicles. This blood supply is also important for wound healing, as the scalp is prone to injuries due to its superficial location.

Anastomosis and Collateral Circulation

Anastomosis with the Supra-orbital Artery

The supratrochlear artery forms important anastomoses with the supra-orbital artery, which also arises from the ophthalmic artery. These connections provide a rich vascular network that ensures consistent blood flow to the forehead and scalp, even if one artery becomes obstructed or damaged. The anastomosis helps create a redundant blood supply, which is crucial for maintaining perfusion in case of trauma or surgical intervention.

Anastomosis with the Superficial Temporal Artery

As the supratrochlear artery ascends toward the scalp, it also forms anastomoses with branches of the superficial temporal artery, which originates from the external carotid artery. This connection ensures that the scalp and forehead receive blood from multiple sources, creating a backup supply that protects against ischemia (insufficient blood flow) in case of injury or disease affecting one of the arteries.

Support for Facial Sensory Function

Coordination with the Supratrochlear Nerve

• The supratrochlear artery runs in close proximity to the supratrochlear nerve, which provides sensory innervation to the forehead and scalp. The artery supports the sensory function of the nerve by ensuring that the tissues supplied by the nerve remain healthy and well-perfused.
• The nerve’s ability to transmit sensory signals from the skin of the forehead depends on the health of the tissues, which is supported by the artery’s blood supply.

Blood Supply to the Upper Nasal Bridge

Vascularization of the Nasal Bridge

• The supratrochlear artery often gives off small dorsal nasal branches that provide blood to the upper nasal bridge. This area is important for both aesthetic appearance and structural integrity. By nourishing the soft tissues and skin around the nasal bridge, the artery ensures that these tissues remain healthy and well-oxygenated.
• The artery’s contribution to the nasal bridge helps maintain the region’s structural support and allows for proper healing in case of injury or surgery.

Role in Healing and Thermoregulation

Support for Wound Healing

The supratrochlear artery’s blood supply is essential for the healing of cuts, abrasions, or surgical wounds on the forehead and scalp. When the skin is damaged, a strong blood supply is needed to deliver oxygen and nutrients to the affected area, promote tissue repair, and remove waste products. The artery’s role in perfusion supports the body’s natural healing processes.

Thermoregulation

The forehead and scalp play important roles in thermoregulation (body temperature regulation). The blood supplied by the supratrochlear artery helps dissipate heat from the body, maintaining temperature balance. When the body becomes too warm, blood vessels in the scalp and forehead dilate, allowing heat to escape. The artery’s blood flow is crucial in this heat exchange process, helping to cool the body.

Clinical Significance

The supratrochlear artery is clinically significant due to its role in supplying blood to the forehead, scalp, and upper nasal bridge. Its superficial course makes it vulnerable to trauma, such as lacerations or blunt force injuries to the forehead, which can result in bleeding. Due to its anastomoses with the supra-orbital and superficial temporal arteries, the supratrochlear artery contributes to the rich vascular network of the forehead and scalp, making it a target in surgical procedures like forehead lifts or scalp flaps in reconstructive surgery.

The artery’s proximity to the supratrochlear nerve also means that it can be affected during facial surgeries or trauma, potentially leading to sensory disturbances. Additionally, its role in providing blood to the forehead makes it relevant in conditions like migraine headaches, where the artery may contribute to vascular changes leading to pain. Proper understanding of its anatomy is crucial for minimizing complications during cosmetic or cranial procedures involving the upper face.