Embryological Development of the Tongue

Introduction

Presenter: Minas
Recommends watching a previous video on pharyngeal arches, clefts, and pouches development for better understanding.
The video aims to be understandable even without prior knowledge of embryology.

Initial Stage: Begins with a blastula formed from the fusion of egg and sperm.
Implantation: Blastula implants into the uterine wall.
Three Germ Layers:
- Ectoderm: Skin and CNS
- Mesoderm: Made of paraxial mesoderm (muscles), intermediate mesoderm (kidneys, gonads), lateral plates
- Endoderm: Gastrointestinal tract

Timeline:
- Week 3: Identification of pharyngeal arches
- Week 4: Tongue begins as a proliferation of the first pharyngeal arch (mandibular arch)
- Week 5: Two lateral swellings and a medial swelling (tuberculum impar) form
- Fifth Month: Lateral swellings overgrow the tuberculum impar to form a majority of the tongue
Formation Details:
- Anterior Two-Thirds: Formed from lateral swellings overgrowing the tuberculum impar
- Root (Posterior Third): Formed from second, third, and fourth pharyngeal arches
- Muscle Origin: Derived from occipital somites from paraxial mesoderm

Motor Innervation: Cranial Nerve 12 (Hypoglossal nerve) supplies all tongue muscles.
Sensory Innervation:
- Anterior Two-Thirds: CN5 (Trigeminal nerve, mandibular branch - lingual branch)
- Posterior Third: Glossopharyngeal nerve
Taste Innervation:
- Anterior Two-Thirds: Facial nerve; valate papillae innervated by glossopharyngeal nerve
- Posterior Third: Glossopharyngeal nerve

Epiglottis Formation:
- Epiglottal swelling from fourth pharyngeal arch becomes epiglottis
- Innervated by the superior laryngeal nerve

Ankyloglossia: Tongue is not freed from the mouth floor due to lack of cell degeneration.
Cleft Tongue: Incomplete fusion of lateral swellings.
Bifid Tongue: Complete lack of fusion, resembling a forked tongue.