The development of the tongue explained in a very simple way.
If you are completely new to embryology and you want to understand it quickly, this should be the first video you watch:
- • Introduction to Embryo...
Post any questions you have about the video below, I read all the comments:
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SUMMARY OF VIDEO FOR YOUR NOTES:
- The tongue appears approximately at 4 weeks in the form of two lateral lingual swellings and one medial swelling which is called the tuberculum impar. These originate from the first pharyngeal pouch.
- A second median swelling, the copula, or hypobranchial eminence, is formed by mesoderm of the second, third, and fourth pharyngeal arches.
- A third medial arch is the epiglottis, formed by the forth arch.
- The lateral swellings increase in size and overgrow the tuberculum impar and then merge forming the anterior 2/3 of the tongue (you can see how nervous supply follows its origin). Sensory innervation (touch) to the body of the tongue is by the mandibular branch of the trigeminal nerve (CN V3).
- The posterior 1/3 of the tongue (root) originates from arches 2, 3, and 4. Sensory innervation is by glossopharyngeal nerve CN IX (you can see in the video how the root of the tongue is mostly from arch 3. I have colour coded it so you can follow it easier on the notes.
- The epiglottis and the extreme posterior part of the tongue are innervated by the superior laryngeal nerve, and develop from the forth arch.
- The muscle of the tongue (motor) originates from occipital somites from paraxial mesoderm. They are innervated by the hypoglossal nerve (CN XII).
- Special sensory innervation, namely taste, to the anterior 2/3 of the tongue is supplied by the facial nerve (chorda tympani branch). This is except for the vallate papillae, which is supplied by CN IX. The posterior 1/3 is supplied by the glossopharyngeal nerve.
CONGENITAL MALFORMATIONS:
- Ankyloglossia (also known as tongue-tie): occurs when the frenulum extends to the tip of the tongue tying it to the floor of the mouth.
- Macroglossia: abnormally large tongue from generalised hypertrophy
- Microglossia: abnormally small tongue that is associated with micrognathia.
- Cleft tongue: incomplete fusion of the lateral lingual swellings posteriorly.
- Bifid tongue: complete failure in the fusion of the lateral lingual swellings.
25 авг 2018
