✅ 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 sources including neural crest cells, paraxial mesoderm, lateral mesoderm, and ectodermal placodes.
Development of Pharyngeal Apparatus
- The development stages in human embryos show similarities to fish embryos, leading to the term "Pharyngeal Apparatus" instead of "Branchial Apparatus."
- The Pharyngeal Apparatus consists of arches, bags, grooves/slits, and membranes; it is crucial for understanding head and neck formation.
Pharyngeal Arches Formation
- Neural Crest cells migrate to form the first pair of pharyngeal arches around the developing pharynx by the end of the fourth week.
- By this time, 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 muscular elements for head/neck muscles, arteries, sensory/motor nerves, and cartilaginous structures forming the skeleton.
Muscle Components & Innervation
- The First Arch contributes to chewing muscles (e.g., digastric muscle), innervated by the lower maxillary branch of the Trigeminal Nerve.
- The Second Arch gives rise to facial expression muscles innervated by the Facial nerve; includes stirrup muscle and hyoid style.
Cartilage Development in Pharyngeal Arches
- Muscles from the Fourth Arch include Cricothyroid and Pharyngeal Constrictors; these are innervated by branches from the vagus nerve.
- Cartilage from each arch forms specific skeletal structures:
- First Arch: Maxilla & Mandibular Process (Meckel's cartilage).
- Second Arch: Reichert Cartilage contributing to stirrup bone & styloid process.
Conclusion on Cartilaginous Structures
- Third Arch cartilage forms parts of hyoid bone while Fourth/Sixth Arch cartilages fuse into larynx components like thyroid cartilage.