✔️📚Short, Practical and Simple
EmbryologyLangman #Medicine #Veterinary #Kinesiology #Biology
Bibliography:
- Netter Atlas of Embriology
- Langman Embryology 13th Edition
- Moore 8th Edition Embryology
- Human embryology and developmental biology Carlson 4th edition
- Human Embryology Armando Valdez
Head and neck
The mesenchyme for the formation of the head region derives from the paraxial and lateral plate mesoderm, the neural crest, and thickened regions of the ectoderm known as ectodermal placodes. The paraxial mesoderm (somites and somitomers) forms a large part of the
membranous and cartilaginous components of the neurocranium (skull), all the voluntary muscles of the craniofacial region, the dermis and connective tissues of the dorsal region of the head, as well as the caudal meninges to the forebrain. The mesoderm of the lateral plate constitutes some laryngeal cartilage (arytenoid and cricoid) and the connective tissue in this region. The neural crest cells originate from the neuroectoderm of the forebrain region, the
midbrain and hindbrain, and migrate ventrally into the pharyngeal arches, and rostral around the forebrain and optic cup to enter the facial region. At these sites they constitute the entire viscerocranium (face) and parts of the membranous and cartilaginous regions of the neurocranium (skull). They also make up the rest of the tissues in these regions, including cartilage, bone, dentin, tendons, dermis, pia mater and arachnoid, sensory neurons and glandular connective tissue. The cells of the ectodermal placodes (epipharyngeal placodes), together with the neural crest, form the neurons of the sensory cranial ganglia V, VII, IX and X.
The most peculiar characteristic of the development of the head and neck is the presence of the pharyngeal arches (the previous concept that was used to name these structures was gill arches, since they somewhat resemble the gills of a fish). These arches appear during the fourth and fifth weeks of development and contribute to the characteristic external appearance of the embryo. Initially, they are made up of accumulations or segments of mesenchymal tissue separated by deep fissures known as pharyngeal clefts. Simultaneously, with the development of the arches and clefts, pharyngeal pockets appear along the lateral walls of the pharynx, the most cranial portion of the anterior intestine. Thus, although the development of the arches, clefts, and pharyngeal pockets is similar to the formation of the gills of fish and amphibians, true gills never form in the human embryo. Thus, for the human embryo, the name pharyngeal (arches, clefts and pockets) has been adopted.
31 июл 2024
