The supra-orbital artery is a branch of the ophthalmic artery, which arises from the internal carotid artery. It plays an important role in supplying blood to the upper part of the face, including the forehead, scalp, and parts of the upper eyelid.
Location
The supra-orbital artery originates from the ophthalmic artery within the orbit. It travels anteriorly through the orbit, above the extraocular muscles, and emerges from the orbit via the supra-orbital foramen or notch in the frontal bone. From this point, it courses upward to supply the forehead, scalp, and surrounding areas. It runs in close proximity to the supra-orbital nerve, providing blood to the skin, muscles, and underlying tissues of the forehead and upper eyelid. Additionally, the artery forms anastomoses with branches of the superficial temporal artery and other arteries that supply the scalp.
Anatomy
The supra-orbital artery is a branch of the ophthalmic artery that provides blood supply to the forehead, scalp, and parts of the upper eyelid. Its course and distribution make it an important vessel in the vascularization of the face and head. Below is a detailed description of the anatomy of the supra-orbital artery.
Origin
The supra-orbital artery originates from the ophthalmic artery, which itself is a branch of the internal carotid artery. The ophthalmic artery arises from the internal carotid artery as it passes through the optic canal and enters the orbit. The supra-orbital artery branches off from the ophthalmic artery as it travels through the orbit, typically after the ophthalmic artery gives rise to the lacrimal artery and other smaller branches.
Course
Intraorbital Segment:
After branching from the ophthalmic artery within the orbit, the supra-orbital artery courses anteriorly, passing superior to the extraocular muscles. It travels along the roof of the orbit, running close to the orbital periosteum and in parallel with the supra-orbital nerve (a branch of the frontal nerve from the ophthalmic division of the trigeminal nerve). It remains above the levator palpebrae superioris muscle, which controls the elevation of the upper eyelid.
Exit through Supra-orbital Foramen:
- The supra-orbital artery exits the orbit through the supra-orbital foramen (or notch), located in the superior rim of the orbit in the frontal bone. The supra-orbital foramen can be a complete foramen or a notch, depending on individual anatomical variation.
- Once it exits the orbit, the artery continues its course onto the forehead.
Extraorbital Segment (Forehead and Scalp):
- After exiting through the supra-orbital foramen, the artery ascends onto the forehead. It travels upwards beneath the skin, running close to the supra-orbital nerve, which provides sensory innervation to the forehead and scalp.
- The artery moves in a superior direction toward the scalp, extending as far as the vertex of the skull. As it ascends, it runs deep to the frontalis muscle and eventually becomes more superficial as it approaches the scalp.
Branches
Muscular Branches:
As the supra-orbital artery travels through the orbit and onto the forehead, it gives off small muscular branches that supply the levator palpebrae superioris muscle and the frontalis muscle. These branches provide vascular support to the muscles involved in eyelid movement and forehead expression.
Cutaneous Branches:
The supra-orbital artery provides cutaneous branches that supply the skin of the forehead and scalp. These branches help nourish the superficial layers of the skin, contributing to the vascularization of the facial tissues.
Periosteal Branches:
Along its course, the supra-orbital artery gives off small periosteal branches that supply the periosteum (the fibrous layer covering the bone) of the frontal bone, ensuring that the bone’s outer layers receive sufficient blood flow.
Anastomoses with Other Arteries:
- As the supra-orbital artery ascends toward the scalp, it forms anastomoses (connections) with other arteries that supply the scalp. These include the supratrochlear artery (a branch of the ophthalmic artery) and branches of the superficial temporal artery, which is a terminal branch of the external carotid artery.
- The anastomosis between the supra-orbital artery and these arteries creates a vascular network that ensures a rich blood supply to the forehead and scalp.
Anatomical Relations
Supra-orbital Nerve:
The supra-orbital artery runs in close proximity to the supra-orbital nerve, which is a branch of the frontal nerve (a division of the trigeminal nerve). This nerve provides sensory innervation to the forehead and scalp. The artery and nerve travel together through the orbit and exit through the supra-orbital foramen.
Levator Palpebrae Superioris Muscle:
The artery runs superior to the levator palpebrae superioris muscle, which is responsible for raising the upper eyelid. The muscular branches of the supra-orbital artery supply this muscle with blood.
Frontalis Muscle:
The artery passes deep to the frontalis muscle on the forehead. The frontalis muscle is involved in elevating the eyebrows and wrinkling the forehead. The supra-orbital artery provides branches that supply blood to this muscle.
Forehead and Scalp:
The artery ascends into the scalp, where it provides vascular supply to the skin and subcutaneous tissues. It runs alongside the supra-orbital nerve as it travels toward the vertex of the skull, forming anastomoses with other arteries that supply the scalp.
Termination
The supra-orbital artery terminates by distributing its branches across the forehead and scalp. As it ascends, the artery becomes more superficial and provides nourishment to the skin, muscles, and periosteum of the frontal bone. Its branches continue to supply the scalp as far as the vertex of the skull, where it anastomoses with branches of the superficial temporal artery and supratrochlear artery.
Function
The supra-orbital artery plays a crucial role in supplying blood to various structures in the forehead, scalp, upper eyelid, and surrounding tissues. It ensures proper nourishment to the skin, muscles, and periosteum in the upper face and head. Below is a detailed description of the specific functions of the supra-orbital artery.
Blood Supply to the Forehead
Nourishment of the Skin
The supra-orbital artery provides critical blood flow to the skin of the forehead. The skin in this region requires a rich blood supply to maintain its structure, provide nutrients, and support wound healing when necessary. The artery ensures that the forehead remains well-nourished, contributing to healthy skin appearance and function.
Support for Subcutaneous Tissues
Beneath the skin, the artery supplies the subcutaneous tissues of the forehead. These tissues, which include fat and connective tissues, require a constant supply of oxygenated blood to function properly. The supra-orbital artery helps maintain the integrity of these layers, ensuring that they are well-perfused.
Blood Supply to the Scalp
Perfusion of the Scalp
As the supra-orbital artery ascends from the forehead to the scalp, it provides blood to the scalp’s skin and underlying tissues. The scalp has a high demand for blood flow, particularly because of its dense hair follicles and need for rapid healing when injured. The supra-orbital artery plays an essential role in delivering oxygenated blood to this region.
Anastomosis with Other Scalp Arteries
The supra-orbital artery forms anastomoses with other arteries that supply the scalp, such as the supratrochlear artery and superficial temporal artery. These anastomoses help create a robust vascular network in the scalp, ensuring that even if one artery is compromised, blood can continue to flow through collateral vessels. This redundancy is vital for maintaining a consistent blood supply to the scalp, which is prone to injury.
Blood Supply to the Muscles
Frontalis Muscle
The supra-orbital artery supplies the frontalis muscle, which is part of the occipitofrontalis muscle group responsible for raising the eyebrows and wrinkling the forehead. This muscle requires adequate blood flow to function properly, as it is involved in facial expressions. The artery’s muscular branches provide the frontalis muscle with the oxygen and nutrients it needs to contract and perform its functions.
Levator Palpebrae Superioris Muscle
Within the orbit, the supra-orbital artery supplies blood to the levator palpebrae superioris muscle, which controls the elevation of the upper eyelid. This is crucial for normal eyelid movement, allowing the eye to open fully and enabling proper vision. By providing blood to this muscle, the artery ensures that the upper eyelid can move efficiently and respond to the brain’s signals.
Blood Supply to the Periosteum
Nourishing the Periosteum of the Frontal Bone
The supra-orbital artery supplies blood to the periosteum of the frontal bone, which is the fibrous layer covering the outer surface of bones. The periosteum plays a vital role in bone health and repair. By providing blood to this layer, the supra-orbital artery ensures that the frontal bone remains nourished and capable of regenerating when damaged.
Blood Supply to the Upper Eyelid
Vascularization of the Upper Eyelid
The artery also sends branches to the upper eyelid, supplying the skin, muscles, and connective tissues of this area. The upper eyelid is crucial for protecting the eye and distributing tears across the ocular surface, and it requires a steady blood supply for proper function. The supra-orbital artery’s contribution to the eyelid ensures that the tissues remain healthy and capable of performing their protective and lubricating roles.
Facilitation of Facial Sensory Function
Collaboration with the Supra-orbital Nerve
The supra-orbital artery runs alongside the supra-orbital nerve, which provides sensory innervation to the forehead and scalp. Although the artery’s function is primarily vascular, its close proximity to the nerve facilitates coordinated support to the skin and tissues of the forehead. The nerve’s sensory function and the artery’s blood supply work together to maintain proper sensation and nourishment in the upper face.
Contribution to Wound Healing and Thermoregulation
Support for Wound Healing
The supra-orbital artery provides essential blood flow to the skin and tissues of the forehead and scalp, playing a crucial role in wound healing. When the skin is injured, an adequate blood supply is necessary to deliver oxygen and nutrients to the site of the wound, support tissue repair, and remove waste products. The supra-orbital artery’s contribution to this process ensures that the skin of the forehead and scalp can heal quickly and effectively after trauma.
Thermoregulation
The skin of the forehead and scalp plays an important role in regulating body temperature, and the blood flow provided by the supra-orbital artery contributes to this thermoregulation. By delivering warm, oxygenated blood to the skin, the artery helps dissipate heat from the head. This is especially important for maintaining a stable body temperature in various environmental conditions.
Collateral Circulation
Anastomosis with Other Arteries
The supra-orbital artery forms anastomoses with other nearby arteries, such as the supratrochlear artery (another branch of the ophthalmic artery) and the superficial temporal artery (a branch of the external carotid artery). These anastomoses provide collateral circulation, meaning that if one artery is blocked or compromised, blood can still reach the tissues through alternative routes. This redundancy helps ensure that the forehead and scalp maintain a consistent blood supply, even in the event of vascular injury or disease.
Clinical Significance
The supra-orbital artery is clinically significant due to its role in supplying blood to the forehead, scalp, upper eyelid, and surrounding structures. It is an important artery in facial and cranial surgeries, particularly in procedures like forehead lifts, scalp flaps, and reconstructive surgeries. Its close relationship with the supra-orbital nerve means that injury to this artery can lead to complications such as hematoma, poor wound healing, or nerve damage, which may result in sensory disturbances in the forehead and scalp.
Additionally, the artery’s superficial course makes it vulnerable to trauma, such as lacerations or fractures of the frontal bone. Vascular conditions, such as arterial occlusions or aneurysms affecting the supra-orbital artery, can compromise blood flow to the forehead and scalp, potentially leading to localized ischemia or delayed wound healing. The artery’s anastomoses with other facial and scalp arteries also make it important in maintaining collateral circulation, ensuring blood supply in case of injury to nearby vessels.
