Anatomy
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Head and Neck
A 20 year old man presents to ED following an alleged assault with a laceration to the lower central part of the midline forehead. He requires a nerve block to close the wound. Which of the following nerves will need to be blocked:
Answer:
The supratrochlear nerve, branch of the ophthalmic nerve, innervates skin of the lower central part of the forehead and conjunctiva and skin of the upper eyelid.Cutaneous Innervation of Face
Anatomy / Head and Neck / Face
Last Updated: 16th June 2022
The trigeminal nerve divides into three major divisions: the ophthalmic (V1), maxillary (V2) and mandibular (V3) nerves which supply the skin of the face.
![By Patrick J. Lynch, medical illustrator (Patrick J. Lynch, medical illustrator) [CC BY 2.5], via Wikimedia Commons](https://mrcemsuccess.com/wp-content/uploads/2016/07/Face-innervation.png)
Cutaneous Innervation of the Head. (Image by Patrick J. Lynch, medical illustrator [CC BY 2.5], via Wikimedia Commons)
Ophthalmic Nerve
The ophthalmic nerve exits the skull through the superior orbital fissure to enter the orbit. It gives rise to five cutaneous branches that supply the face:
- the supraorbital nerve (innervating skin of the upper eyelid and conjunctiva and the skin of the upper forehead extending back to the middle of the scalp)
- the supratrochlear nerve (innervating skin of the lower central part of the forehead and conjunctiva and skin of the upper eyelid)
- the infratrochlear nerve (innervating the medial half of the upper eyelid and the skin in the area of the medial angle and the bridge of the nose)
- the lacrimal nerve (innervating the lateral half of the upper eyelid and the skin in the area of the lateral angle)
- the external nasal nerve (innervating the anterior lower half of the nose).
Maxillary Nerve
The maxillary nerve exits the skull through the foramen rotundum and gives rise to three cutaneous branches that supply the face:
- the zygomaticotemporal nerve (innervating a small area of the anterior temple above the zygomatic arch)
- the zygomaticofacial nerve (innervating a small area of skin over the zygomatic bone)
- the infraorbital nerve (innervating the lower eyelid, the cheek, the side of the nose and the upper lip).
Mandibular Nerve
The mandibular nerve exits the skull through the foramen ovale and gives rise to three cutaneous branches that supply the face:
- the auriculotemporal nerve (innervating the external acoustic meatus, the surface of the tympanic membrane and a large area of the temple)
- the buccal nerve (innervating the cheek)
- the mental nerve (innervating the skin and mucous membranes of the lower lip and the skin of the chin).
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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 |
