✅ EMBRIOLOGÍA de la CABEZA y el CUELLO (Parte 1°)👅🙇🏻♀️
Head and Neck Embryology: Part 1
Introduction to Head and Neck Embryology
- The video introduces the topic of Head and Neck Embryology, highlighting a previous video with audio issues that prompted this new recording.
- The Cephalic Region is defined as a complex area where structures originate from various embryonic sources, including the neural crest (blue), paraxial mesoderm (red), lateral mesoderm (yellow), and ectodermal placodes.
Development of Pharyngeal Apparatus
- The head and neck regions in a 4-week-old human embryo resemble those of fish embryos at similar developmental stages, leading to historical references to the "Branchial Apparatus."
- Currently, the term "Pharyngeal Apparatus" is used, consisting of arches, bags, grooves/slits, and membranes.
Pharyngeal Arches Formation
- Pharyngeal arches develop as neural crest cells migrate; the first pair appears as lateral elevations around the developing pharynx.
- By the end of week four, four pairs of pharyngeal arches are visible externally; rudimentary fifth and sixth arches are not visible.
Structure of Pharyngeal Arches
- Each arch comprises mesenchymal tissue covered by ectoderm externally and endoderm internally. Key components include muscles, arteries, nerves, and cartilage.
Muscle Components & Innervation
- The First Arch contributes to chewing muscles like the digastric anterior belly; innervated by the lower maxillary branch of the Trigeminal Nerve.
- The Second Arch gives rise to muscles such as the stirrup muscle and facial expression muscles; these are innervated by the Facial Nerve.
- The Third Arch forms stylopharyngeus muscle innervated by Glossopharyngeal Nerve; while Fourth Arch includes cricothyroid muscle innervated by superior laryngeal branch of Vagus Nerve.
Cartilage Development in Pharyngeal Arches
- The First Arch consists of maxillary (dorsally located) and mandibular processes; it leads to formation of maxillae, zygomatic bones, temporal bone, and jaw structures.
- Meckel's cartilage within mandibular process persists partially forming parts like anvil and hammer during later development.
Cartilaginous Structures from Other Arches
- Reichert's cartilage from Second Arch contributes to stirrup bone among others; Third Arch forms lower body portion & greater horn of hyoid bone.
- Cartilage from Fourth & Sixth Arches fuses into larynx cartilages including thyroid & cricoid cartilages.
Conclusion