Lacrimal artery

The lacrimal artery is a significant branch of the ophthalmic artery that supplies blood to the lacrimal gland, the conjunctiva, and parts of the eyelids. It is an essential vessel within the orbit and is involved in the vascularization of the structures responsible for tear production and ocular surface protection. The lacrimal artery also contributes to the blood supply of adjacent tissues, including some of the extraocular muscles.

Location

The lacrimal artery originates from the ophthalmic artery shortly after it enters the orbit through the optic canal. It runs along the superior border of the lateral rectus muscle towards the lacrimal gland, which is located in the superolateral part of the orbit. Along its course, the artery gives off branches that supply nearby structures, including parts of the lateral conjunctiva and the eyelids. The lacrimal artery also anastomoses with other orbital vessels, such as branches from the middle meningeal artery.

Anatomy

The lacrimal artery is an important branch of the ophthalmic artery and plays a key role in supplying blood to various structures within the orbit. It follows a specific anatomical course and gives rise to several smaller branches that serve nearby tissues, including the lacrimal gland, the eyelids, and parts of the conjunctiva. Below is a detailed description of the anatomy of the lacrimal artery.

Origin

The lacrimal artery typically arises from the ophthalmic artery, which itself is a branch of the internal carotid artery. The lacrimal artery originates soon after the ophthalmic artery enters the orbit through the optic canal, and it is usually one of the larger branches of the ophthalmic artery. In some anatomical variations, the lacrimal artery may arise from a common trunk with other branches of the ophthalmic artery.

Course

The course of the lacrimal artery can be divided into several key segments as it travels through the orbit to supply various structures:

• Initial Segment (Proximal to Lateral Rectus Muscle): After branching from the ophthalmic artery, the lacrimal artery runs laterally and anteriorly along the superior margin of the lateral rectus muscle. It courses toward the lateral wall of the orbit, following a path that brings it close to the lacrimal gland.
• Passing Near the Lateral Rectus Muscle: The artery continues to run along the upper border of the lateral rectus muscle, maintaining a lateral course as it approaches the superolateral portion of the orbit. As it travels along this muscle, the artery supplies small branches that nourish the lateral rectus muscle itself.
• Approach to the Lacrimal Gland: As it nears the superolateral part of the orbit, the lacrimal artery enters the lacrimal gland, supplying this gland with its primary blood supply. The lacrimal gland, responsible for tear production, is located in the fossa for the lacrimal gland within the frontal bone.

Branches of the Lacrimal Artery

The lacrimal artery gives off several important branches that supply various structures in and around the orbit:

• Lacrimal Gland Branches: The primary branches of the lacrimal artery are those that directly supply the lacrimal gland. These branches penetrate the gland and provide it with the blood supply necessary for maintaining tear production and glandular health.
• Zygomatic Branches:
  • The lacrimal artery gives rise to the zygomatic branches, which leave the orbit through the zygomatic bone via small foramina (zygomaticofacial and zygomaticotemporal foramina). These branches supply the skin of the zygomatic region of the face (the cheek and temporal areas).
  • These branches include:
    • Zygomaticofacial Artery: This branch supplies blood to the zygomaticofacial region of the face, particularly the skin and soft tissues around the cheekbone.
    • Zygomaticotemporal Artery: This branch travels toward the temporal region of the skull, supplying blood to the skin and underlying tissues in this area.
• Recurrent Meningeal Artery: The lacrimal artery also gives rise to a recurrent meningeal branch. This small branch re-enters the cranial cavity through the superior orbital fissure or another foramen. It supplies the dura mater, contributing to the vascularization of the meninges in the anterior cranial fossa. The recurrent meningeal artery often anastomoses with branches of the middle meningeal artery, forming an important connection between the intra-orbital and cranial vasculature.
• Lateral Palpebral Arteries:
  • The lacrimal artery gives off two important lateral palpebral arteries (superior and inferior) that supply the lateral parts of the upper and lower eyelids. These branches form an anastomosis with the medial palpebral arteries, which arise from the ophthalmic artery, creating a robust blood supply network for the eyelids.
  • Superior Lateral Palpebral Artery: This branch supplies blood to the lateral part of the upper eyelid and anastomoses with the medial palpebral artery.
  • Inferior Lateral Palpebral Artery: This branch supplies the lateral part of the lower eyelid and also anastomoses with the medial palpebral artery.
• Conjunctival Branches: The lacrimal artery sends small branches to the lateral portion of the conjunctiva, providing vascular supply to this thin, transparent layer that covers the white part of the eye and lines the inside of the eyelids.

Anatomical Relations

• Lateral Rectus Muscle: The lacrimal artery travels along the superior border of the lateral rectus muscle, and it supplies small branches to this extraocular muscle, which is responsible for lateral eye movement. The artery runs in close proximity to the muscle before continuing toward the lacrimal gland.
• Lacrimal Gland: The lacrimal artery is the main arterial supply to the lacrimal gland, which is located in the superolateral part of the orbit. The artery enters the gland and supplies it with blood, ensuring the gland’s function in tear production.
• Zygomatic Bone: The zygomatic branches of the lacrimal artery exit the orbit via the zygomaticofacial and zygomaticotemporal foramina, providing blood to the cheek and temporal regions of the face. These branches have anatomical relationships with the zygomatic bone and surrounding facial structures.
• Palpebral Arteries: The lateral palpebral arteries, which are branches of the lacrimal artery, are closely related to the lateral aspects of the upper and lower eyelids. These arteries anastomose with the medial palpebral arteries to ensure adequate blood flow to the entire eyelid.

Anastomoses

The lacrimal artery forms several important anastomoses, providing collateral blood flow between different arterial systems. These include:

• Anastomosis with the Middle Meningeal Artery: The recurrent meningeal branch of the lacrimal artery anastomoses with the middle meningeal artery, creating a connection between the orbital and cranial blood supplies.
• Anastomosis with the Medial Palpebral Arteries: The lateral palpebral arteries form an anastomosis with the medial palpebral arteries to ensure that the eyelids receive sufficient blood from both the lateral and medial aspects.

Termination

The lacrimal artery terminates by supplying the lacrimal gland and the lateral parts of the eyelids through its lateral palpebral branches. Its small branches to the conjunctiva and the recurrent meningeal artery also represent its distal terminal points.

Function

The lacrimal artery plays a critical role in supplying blood to several structures within the orbit and the surrounding facial regions. Below is a detailed breakdown of its functions, based on the anatomical regions it supplies.

Blood Supply to the Lacrimal Gland

Support for Tear Production

• The lacrimal artery’s primary function is to supply blood to the lacrimal gland, which is responsible for producing the aqueous layer of the tear film. This tear film keeps the eye’s surface lubricated, protects against infection, and maintains a clear optical surface.
• By providing oxygenated blood and nutrients to the lacrimal gland, the artery ensures the gland’s functionality in producing tears. Without this supply, the gland would be unable to maintain its secretion, leading to dry eyes and potential damage to the ocular surface.

Blood Supply to the Extraocular Muscles

Supplying the Lateral Rectus Muscle

• The lacrimal artery provides blood to the lateral rectus muscle, which is one of the six extraocular muscles responsible for eye movement. The lateral rectus muscle controls the abduction of the eye, allowing the eye to move outward, away from the midline.
• By ensuring the lateral rectus muscle receives an adequate blood supply, the lacrimal artery helps maintain proper eye movement and coordination. This is critical for binocular vision and smooth pursuit of moving objects.

Blood Supply to the Zygomatic Region

Zygomaticofacial and Zygomaticotemporal Branches

• The zygomaticofacial and zygomaticotemporal branches of the lacrimal artery supply the skin, muscles, and soft tissues of the zygomatic (cheek) and temporal regions of the face. These branches exit the orbit through small foramina in the zygomatic bone.
• These branches ensure that the lateral regions of the face receive sufficient blood flow, contributing to the maintenance of facial skin, underlying muscles, and soft tissues.

Blood Supply to the Eyelids

Lateral Palpebral Arteries

• The superior and inferior lateral palpebral arteries, which are branches of the lacrimal artery, supply blood to the lateral parts of the upper and lower eyelids. These arteries form anastomoses with the medial palpebral arteries to ensure a comprehensive blood supply to the entire eyelid.
• By nourishing the eyelids, the lacrimal artery contributes to maintaining eyelid health, which is essential for their protective role. The eyelids help distribute the tear film across the eye, protect the eye from debris, and regulate the amount of light that enters the eye.

Nourishing the Eyelid Tissues

The lateral palpebral arteries supply oxygenated blood to the eyelid’s muscles, skin, and tarsal plates. This ensures that these tissues remain healthy and functional, contributing to proper blinking and eye protection.

Blood Supply to the Conjunctiva

Conjunctival Branches

• The lacrimal artery provides small branches that supply the lateral portion of the conjunctiva, which is the transparent membrane covering the white part of the eye (sclera) and lining the inside of the eyelids.
• These conjunctival branches help maintain the health and function of the conjunctiva, contributing to its role in protecting the eye from infection and maintaining a stable ocular surface.

Blood Supply to the Dura Mater

Recurrent Meningeal Artery

• The lacrimal artery gives rise to the recurrent meningeal artery, which re-enters the cranial cavity through the superior orbital fissure or another nearby foramen to supply the dura mater in the anterior cranial fossa.
• This artery contributes to the blood supply of the meninges, the protective layers surrounding the brain. By providing blood to the dura mater, the lacrimal artery plays a small but important role in maintaining the health and integrity of the meningeal tissues.

Role in Collateral Circulation

Anastomoses with Other Arteries

• The lacrimal artery forms several important anastomoses, including connections with the middle meningeal artery through its recurrent meningeal branch and with the medial palpebral arteries in the eyelids.
• These anastomoses provide collateral blood flow, ensuring that the regions supplied by the lacrimal artery have a backup blood supply in case of blockages or disruptions. This is particularly important for maintaining blood flow to critical areas like the lacrimal gland, eyelids, and orbital structures.

Clinical Significance of the Lacrimal Artery

The lacrimal artery is clinically significant because of its crucial role in supplying blood to the lacrimal gland, which produces tears, and other essential structures within the orbit such as the lateral rectus muscle, eyelids, and conjunctiva. Damage or occlusion of the lacrimal artery can lead to various complications, including dry eye syndrome due to impaired tear production, which can result in ocular surface damage and an increased risk of eye infections.

Additionally, the lacrimal artery’s branches supply the eyelids and extraocular muscles. If its blood flow is compromised, it could lead to dysfunction of the lateral rectus muscle, resulting in strabismus (misalignment of the eyes) or diplopia (double vision). Injuries or orbital surgeries involving the lacrimal artery may lead to ischemia in the surrounding structures, which can affect vision and eye movement.