Anatomy
Cranial Nerve Lesions
The inferior alveolar nerve supplies all of the following EXCEPT for the:
Answer:
The inferior alveolar nerve carries general sensation from the lower teeth and associated gingivae, mucosa and skin of the lower lip and skin of the chin and gives rise to a motor branch which innervates the mylohyoid muscle and the anterior belly of the digastric muscle. The tensor veli palatini muscle is innervated by the nerve to medial pterygoid (of mandibular nerve (CN V3)).Cranial Nerve V3: Mandibular Nerve
Anatomy / Cranial Nerve Lesions / Head and Neck / Infratemporal Fossa
Last Updated: 23rd April 2020
The mandibular nerve is the largest of the three divisions of the trigeminal nerve, and unlike the other two divisions, it is both motor and sensory.
Table: Overview of the Mandibular Nerve
| Cranial Nerve | Mandibular Nerve (V3) |
|---|---|
| Key anatomy | Arises in middle cranial fossa, exits skull through foramen ovale, enters infratemporal fossa |
| Sensory function | Lower lip and chin, lower teeth and gingiva, floor of oral cavity, anterior two-thirds of tongue, temple, TMJ, external ear and external auditory meatus |
| Motor function | Muscles of mastication, tensor tympani, tensor veli palatini, mylohyoid, anterior belly of digastric |
| Special function | Postganglionic parasympathetic fibres to parotid gland |
Functional Overview
Through its branches the mandibular nerve carries:
- General sensation from:
- the lower teeth and associated gingivae
- the anterior two-thirds of the tongue
- mucosa on the floor of the oral cavity
- mucosa and skin of the lower lip and chin
- skin over the temple
- the external ear, external auditory meatus and outer tympanic membrane
- the temporomandibular joint
- part of the cranial dura mater
- Motor innervation to:
- the muscles of mastication (masseter, temporalis, medial and lateral pterygoids)
- the tensor tympani muscle of the middle ear
- the tensor veli palatini muscle of the soft palate
- the mylohyoid muscle
- the anterior belly of the digastric muscle
- Postganglionic parasympathetic fibres to:
- the parotid gland
Anatomical Course
The large sensory part originates from the trigeminal ganglion in the middle cranial fossa and descends vertically through the foramen ovale and enters the infratemporal fossa between the tensor veli palatini muscle and the upper head of the lateral pterygoid muscle. The small motor root passes medial to the trigeminal ganglion in the cranial cavity, then passes through the foramen ovale and immediately joins the sensory part of the mandibular nerve. All of the branches of the mandibular nerve originate in the infratemporal fossa.
Mandibular Nerve. (Image by Henry Vandyke Carter [Public domain], via Wikimedia Commons)
Branches
Table: Branches of the Mandibular Nerve
| Branch | Origin | Function |
|---|---|---|
| Meningeal Branch | Main Trunk | Sensory: Dura mater of middle cranial fossa and mastoid cells |
| Medial Pterygoid Nerve | Main Trunk | Motor: Medial pterygoid, tensor tympani, tensor veli palatini |
| Buccal Nerve | Anterior Division | Sensory: Skin and mucosa over cheek |
| Masseteric Nerve | Anterior Division | Motor: Masseter |
| Deep Temporal Nerves | Anterior Division | Motor: Temporalis |
| Lateral Pterygoid Nerve | Anterior Division | Motor: Lateral pterygoid |
| Auriculotemporal Nerve | Posterior Division | Sensory: Skin over temple, external ear, external auditory meatus, outer tympanic membrane, TMJ.
Special: Carries parasympathetic fibres from glossopharyngeal nerve to parotid gland |
| Inferior Alveolar Nerve | Posterior Division | Sensory: Lower teeth and associated gingiva, mucosa and skin of lower lip and skin of chin
Motor: Mylohyoid, anterior belly of digastric |
| Lingual Nerve | Posterior Division | Sensory: Anterior two-thirds of tongue, floor of oral cavity |
Soon after the motor and sensory roots join, the mandibular nerve gives rise to a small sensory meningeal branch (supplying dura mater of the middle cranial fossa and mastoid cells) and the nerve to the medial pterygoid (innervating the medial pterygoid, the tensor tympani and the tensor veli palatini muscles).
The nerve then divides into an anterior and posterior division.
The anterior division gives rise to:
- The buccal nerve (sensory - innervating the skin and mucosa over the cheek)
- The masseteric nerve (innervating the masseter muscle)
- The deep temporal nerves (innervating the temporalis muscle)
- The nerve to the lateral pterygoid (innervating the lateral pterygoid muscle)
The posterior division gives rise to:
- The auriculotemporal nerve
- The lingual nerve
- The inferior alveolar nerve
The auriculotemporal nerve carries general sensation from skin over a large area of the temple, the external ear, the external auditory meatus, the outer tympanic membrane and the temporomandibular joint. It also delivers postganglionic parasympathetic fibres from the glossopharyngeal nerve to the parotid gland.
The inferior alveolar nerve initially gives off a muscular branch which innervates the mylohyoid muscle and the anterior belly of the digastric muscle. and then supplies the lower teeth (molars and premolars) with sensory branches whilst in the mandibular canal. Anteriorly it gives rise to the mental nerve which carries sensation from the mucosa and skin of the lower lip and the skin of the chin and then terminates as the mandibular incisive nerve which innervates the lower canines and incisors.
The lingual nerve carries general sensation from the anterior two-thirds of the tongue, oral mucosa on the floor of the oral cavity and lingual gingiva associated with the lower teeth. It also carries nerve fibers of the chorda tympani nerve of the facial nerve, which provides special sensation (taste) to the anterior two-thirds of the tongue as well as parasympathetic and sympathetic fibers.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
