The infra-orbital nerve is a sensory branch of the maxillary division (V2) of the trigeminal nerve (cranial nerve V). It provides sensation to the lower eyelid, upper lip, side of the nose, and part of the cheek. The nerve also supplies sensory fibers to the upper teeth and gums.
Location
The infra-orbital nerve emerges from the maxillary nerve (V2) within the pterygopalatine fossa. It travels through the infra-orbital groove and then enters the infra-orbital canal located within the maxillary bone. The nerve exits the canal through the infra-orbital foramen, located below the orbit, just under the lower edge of the eye socket. After emerging from the infra-orbital foramen, it fans out to supply sensory innervation to the skin of the face, including the lower eyelid, upper lip, and parts of the nose and cheek.
Structure and Anatomy
Origin
The infra-orbital nerve is a direct continuation of the maxillary nerve (V2), which is the second division of the trigeminal nerve (cranial nerve V). It arises in the pterygopalatine fossa, a deep space behind the maxilla, after the maxillary nerve passes through the foramen rotundum from the middle cranial fossa.
Course in the Pterygopalatine Fossa
After originating from the maxillary nerve in the pterygopalatine fossa, the infra-orbital nerve travels anteriorly. As it moves forward, it gives off several branches within the fossa, including the posterior superior alveolar nerve, which innervates the posterior upper teeth. The infra-orbital nerve then continues its journey through the inferior orbital fissure, a gap between the maxilla and the sphenoid bone, and enters the orbit.
Path in the Orbit: Infra-orbital Groove and Canal
Upon entering the orbit, the infra-orbital nerve runs along the infra-orbital groove, located on the floor of the orbit, within the maxillary bone. It continues anteriorly in this groove, which transitions into the infra-orbital canal. The infra-orbital canal is a bony tunnel in the maxilla that guides the nerve toward its exit point on the face. As the nerve travels through this canal, it gives off two sets of branches:
- Middle Superior Alveolar Nerve: These branches supply sensory innervation to the upper premolars and adjacent maxillary sinus.
- Anterior Superior Alveolar Nerve: These branches provide sensory innervation to the upper incisors and canines, as well as contributing to the sensory innervation of the maxillary sinus.
Exit through the Infra-orbital Foramen
The infra-orbital nerve exits the infra-orbital canal through the infra-orbital foramen, a small opening located on the anterior surface of the maxilla, just below the lower margin of the orbit. This foramen is typically found in line with the pupil when looking forward, and it serves as the exit point for the nerve as it reaches the surface of the face.
Branching on the Face
After emerging from the infra-orbital foramen, the infra-orbital nerve divides into several smaller branches that innervate the skin of the face. These branches include:
- Palpebral Branches: These branches ascend to provide sensation to the lower eyelid and the skin around the orbit.
- Nasal Branches: These branches innervate the side of the nose, including the upper part of the nasal vestibule.
- Labial Branches: These branches descend to supply sensory innervation to the skin and mucosa of the upper lip, and they also provide sensation to the oral mucosa covering the maxillary alveolar process (upper gum).
Relationship with Surrounding Structures
The infra-orbital nerve travels close to several important anatomical structures:
- Maxillary Sinus: As the nerve travels through the infra-orbital canal, it is closely associated with the maxillary sinus, with its branches (particularly the anterior and middle superior alveolar nerves) innervating parts of the sinus mucosa.
- Teeth: The nerve’s alveolar branches innervate the upper teeth, providing sensory information from the upper dentition.
- Facial Muscles and Skin: The infra-orbital nerve’s terminal branches spread across the face, running deep to the facial muscles and supplying sensory fibers to the skin of the lower eyelid, upper lip, and lateral part of the nose.
Function
The infra-orbital nerve is a purely sensory nerve that provides sensation to the middle portion of the face, including the lower eyelid, nose, upper lip, and upper teeth. Below are the detailed functions of the nerve, broken down into the regions it innervates.
Sensory Innervation to the Skin of the Lower Eyelid
One of the primary functions of the infra-orbital nerve is to supply sensory fibers to the skin of the lower eyelid. Its palpebral branches ascend after the nerve exits through the infra-orbital foramen to innervate:
- Lower eyelid skin: The nerve provides tactile sensation, detecting light touch, pressure, and pain from the skin in this area.
- Periorbital region: It also innervates the skin just below the orbit, giving feedback on temperature and touch in this sensitive area.
Sensory Innervation to the Side of the Nose
The nasal branches of the infra-orbital nerve provide sensation to the lateral aspect of the nose, including:
- Lateral nasal skin: The nerve relays sensory information from the side of the nose, detecting changes in temperature, pain, and tactile stimuli.
- Nasal vestibule: The infra-orbital nerve also supplies the upper part of the nasal vestibule (the entrance to the nasal cavity), helping detect any irritation or discomfort caused by foreign bodies or nasal obstruction.
Sensory Innervation to the Upper Lip and Oral Mucosa
The labial branches of the infra-orbital nerve descend from the infra-orbital foramen to innervate:
- Upper lip: The nerve provides sensation to the skin of the upper lip, allowing for the detection of tactile stimuli, pressure, and temperature. It is particularly important for everyday activities like eating, speaking, and kissing, where tactile feedback is crucial.
- Oral mucosa of the upper lip: Inside the mouth, the infra-orbital nerve supplies sensation to the mucosa of the upper lip, detecting texture and temperature in the oral cavity.
Sensory Innervation to the Upper Teeth and Gums
The infra-orbital nerve is responsible for providing sensory innervation to the upper teeth and associated structures through its alveolar branches:
- Anterior Superior Alveolar Nerve: This branch supplies sensation to the upper incisors and canines. It detects pain, pressure, and temperature, especially during dental issues like cavities or trauma.
- Middle Superior Alveolar Nerve: This branch provides sensory input to the premolars and sometimes the first molar. It conveys sensory feedback from these teeth, helping in detecting dental pain or discomfort.
- Gingiva (gums): The nerve also supplies the upper gingiva (gums), allowing for sensation of pain, pressure, and irritation in the gum tissue, which is important in maintaining oral health and detecting issues like gingivitis.
Sensory Innervation to the Maxillary Sinus
The infra-orbital nerve, through its anterior and middle superior alveolar branches, supplies sensory innervation to the maxillary sinus. These branches help detect changes in the sinus, such as:
Pain and pressure: The nerve fibers help sense any inflammation, infection, or increased pressure within the maxillary sinus, which is common in sinusitis.
General Tactile and Pain Sensation
In general, the infra-orbital nerve is responsible for conveying sensory information from the middle portion of the face, including:
- Touch and Pressure: It provides the ability to feel light and firm touches, such as when the face comes into contact with objects or during grooming activities.
- Pain Sensation: The infra-orbital nerve plays a critical role in detecting pain, such as from trauma, infections, dental issues, or facial injuries. It helps the body respond to potential damage by signaling the brain to take protective actions.
- Temperature Sensation: The nerve also conveys temperature sensations, allowing the skin, oral mucosa, and teeth to detect changes in hot and cold, which is essential for protecting these structures from injury due to extreme temperatures.
Clinical Significance
The infra-orbital nerve is clinically significant due to its sensory innervation of the midface, including the lower eyelid, upper lip, nose, and upper teeth. Injury or damage to this nerve can result from trauma, such as facial fractures (particularly orbital or maxillary fractures), surgical procedures, or dental treatments, leading to infra-orbital nerve neuropathy. This can cause numbness, tingling, or loss of sensation in the areas it innervates, including the upper lip, cheek, and teeth.
The nerve is also commonly involved in infra-orbital nerve block, a procedure used to provide local anesthesia during facial or dental surgeries, or for pain management. Additionally, compression or irritation of the infra-orbital nerve can result in facial pain, such as in trigeminal neuralgia, causing severe, sharp pain in the areas supplied by the nerve. Recognizing its anatomical course is crucial for preventing complications during facial surgeries, maxillofacial procedures, and dental interventions.
