Anatomy
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Head and Neck
A patient presents to ED complaining of an altered taste sensation. Taste sensation from the anterior two-thirds of the tongue is carried by which of the following nerves:
Answer:
Taste from the anterior two-thirds of the tongue is carried by the chorda tympani, branch of the facial nerve.Tongue
Anatomy / Head and Neck / Mouth and Hard Palate
Last Updated: 11th April 2019
The tongue is a muscular structure that forms part of the floor of the oral cavity and part of the anterior wall of the oropharynx. The anterior two-thirds of the tongue are in the oral cavity. The posterior root of the tongue is attached to the mandible and the hyoid bone. The anterior wall of the oropharynx inferior to the oropharyngeal isthmus is formed by the upper part of the posterior one-third of the tongue.
A pair of mucosal pouches (valleculae), one on each side of the midline, between the base of the tongue and epiglottis, are depressions formed between the midline mucosal fold and two lateral folds that connect the tongue to the epiglottis.
![By OpenStax [CC BY 4.0], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2016/07/tongue-1024x542.jpg)
Tongue. (Image by OpenStax [CC BY 4.0], via Wikimedia Commons)
Papillae and Lingual Tonsil
The oral (anterior two-thirds) and pharyngeal (posterior one-third) surfaces are separated by a V-shaped terminal sulcus of the tongue. The superior surface of the oral part of the tongue is covered by papillae, the majority of which have taste buds on their surface. The mucosa of the pharyngeal surface of the tongue is irregular, because of the many small nodules of lymphoid tissue in the submucosa, collectively known as the lingual tonsil.
![By Lesion (Own work) [CC BY-SA 3.0], via Wikimedia Commons](https://primary-cdn.frcemsuccess.com/wp-content/uploads/2016/07/papillae-tongue.jpg)
Papillae of the Tongue. (Image by Lesion (Own work) [CC BY-SA 3.0], via Wikimedia Commons)
Innervation
- General sensation from the anterior two-thirds of the tongue is carried by the lingual nerve, branch of the mandibular nerve.
- Taste from the anterior two-thirds of the tongue is carried by the chorda tympani, branch of the facial nerve.
- Taste and general sensation from the posterior one-third of the tongue is carried by the glossopharyngeal nerve.
- All muscles of the tongue are innervated by the hypoglossal nerve, except for the palatoglossus, which is innervated by the vagus nerve.
Lymphatic Drainage
All lymphatics from the tongue ultimately drain into the deep cervical chain of nodes along the internal jugular vein. The pharyngeal part of the tongue drains through the pharyngeal wall directly into mainly the jugulo-omohyoid node of the deep cervical chain. The oral part of the tongue drains both directly into the deep cervical nodes and indirectly into these nodes by passing first through the mylohyoid muscle and into submental and submandibular nodes.
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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 |
