Regional Anatomy & Nerve Blocks for Infraorbital, Maxillary, Mandibular, Alveolar, Mental, & Cornual | Animal Husbandry & Veterinary Science Optional for UPSC PDF Download

The Infraorbital Nerve

• The infraorbital nerve is like a pathway that starts from the maxillary nerve and travels through a canal in the skull called the infraorbital canal.
• It comes out through a small hole called the infraorbital foramen under the eye.
• When it's inside the canal, it gives feeling to the upper cheek teeth, gums, and the skin around the upper lip and nose.
• It splits into two smaller branches: one goes to the nose and the other to the upper lip.
• To numb this nerve, doctors inject medicine into the infraorbital canal through the infraorbital foramen.
• In horses, this hole is found along a line from the inside corner of the eye to the nostril, a bit in front of a bony ridge on the face.
• Muscles cover this hole, but by pressing one muscle upward, doctors can feel the hole's edge and insert a needle to block the nerve.

Fig: Blockdng the infraorbltal nerve

Maxillary Nerve

• The maxillary nerve is one of the twelve cranial nerves and is the largest of them.
• It is a mixed nerve, meaning it contains both sensory and motor fibers.
• The nerve originates from the pons, a part of the brainstem, and also receives contributions from the fourth ventricle.
• Its sensory root arises from the pons and gives rise to the Gasserian ganglion, while the motor root also originates from the pons.

Branches of the Maxillary Nerve:

1. Ophthalmic Branch:

   • This sensory branch emerges from the Gasserian ganglion and exits the cranial cavity through the foramen rotundum.
   • It supplies sensory fibers to various structures in the orbit and face.
   • Divides into smaller branches including:
     • Frontal branch: Supplies sensation to the upper eyelid and forehead.
     • Lacrimal branch: Innervates the lacrimal gland, frontal sinus, and skin over the temple.
     • Nasopalpebral branch: Provides sensation to the lower eyelid, inner canthus, and nasal mucous membrane.

2. Superior Maxillary Branch:

   • This sensory branch also arises from the Gasserian ganglion and exits the cranial cavity through the foramen rotundum.
   • It supplies sensation to the upper teeth, gums, cheek, and upper lip.
   • Gives off branches including:
     • Orbital branches: Supply sensation to the eyelids and skin around the orbit.
     • Posterior palatine branch: Innervates the soft palate.
     • Anterior palatine branch: Supplies sensation to the hard palate and gums.
     • Spheno-palatine branch: Provides sensation to the nasal mucous membrane.
     • Superior dental and alveolar branches: Supply the upper cheek teeth, gums, and alveolar periosteum.
     • Terminal branches: Nasal and labial branches that supply the nostrils and upper lip.

3. Inferior Maxillary Division:

   • Formed by the union of sensory and motor roots.
   • It exits the cranial cavity through the foramen ovale and provides sensory and motor innervation to the lower face and oral cavity.

Specific Branches of the Inferior Maxillary Division:

• Pterygoid branches: Innervate the external and internal pterygoid muscles.
• Masseteric branch: Supplies sensation to the masseter muscle.
• Temporal branches: Provide sensory fibers to the temporalis muscle.
• Buccinator branch: Innervates the buccal muscles, mucous membrane of the cheek, and buccal glands.
• Superficial temporal branch: Supplies sensory fibers to the skin over the masseter.
• Lingual branch: Provides sensation to the anterior two-thirds of the tongue and its papillae.

Pathway and Termination:

• The inferior maxillary nerve travels downwards and forwards between the two pterygoid muscles, then enters the mandibular foramen.
• It runs along the mandibular canal, providing sensory innervation to the lower teeth, gums, and chin.
• Finally, it exits the mandibular canal through the mental foramen and terminates by branching into labial filaments that supply sensation to the lower lip.

The Mental Nerve

• The mental nerve is a part of the mandibular nerve that comes out of the jawbone.
• It's responsible for providing sensation to the lower lip and chin.

Termination and Branches:

• After emerging from the jawbone, the mental nerve divides into six to eight smaller branches.
• These branches spread out and provide feeling to the lower lip and chin area.

Locating the Mental Foramen:

• You can find the mental foramen, where the nerve exits the jawbone, by feeling just below the corner of the lower lip with your thumb and index finger.
• Apply gentle pressure upwards, and you'll feel a slight dip or hollow in the bone. That's the mental foramen.

Using the Mental Foramen:

• Understanding the location of the mental foramen is useful for procedures like dental anesthesia.
• Blocking the nerve at this point can numb the lower lip, making dental procedures more comfortable for the patient.

Fig: Blocking the mental nerve in the mandibular canal

The Mandibular Alveolar Nerve

• Part of the mandibular nerve, along with the lingual nerve.
• Travels through the mandibular foramen and the mandibular canal.

Course and Branches:

• Travels within the mandibular canal.
• Gives off dental branches to lower cheek teeth, alveolar periosteum, and gums.

Locating the Mandibular Foramen:

• Found at the intersection of a line along the chewing surface of lower teeth and a line from the outer corner of the eye.
• Situated on the inner side of the jaw's bony projection (ramus mandibuli).

Anesthesia Injection Point:

• The anesthesia injection is given at the mandibular foramen.
• Successful injection results in numbness of the lower jaw, teeth, and lower lip.

Fig: Blocking the mandibular alveolar nerve

The Cornual Nerve in the Ox

• Part of the lacrimal nerve, which comes from the ophthalmic nerve (a key part of the trigeminal nerve).

Path and Location:

• Originates from the ophthalmic nerve and goes through the tissues around the eye.
• Runs along the frontal crest (bony part on the forehead) to reach the base of the horn.

Superficial Transition:

• As it travels from the eye to the horn base, it becomes more visible on the surface.

Anesthesia Procedure:

• Best performed 2 to 3 cm below the horn base.
• Needle inserted just below the frontal crest, close to its margin.
• This numbs the horn and the surrounding skin.