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The face and neck development of the human embryo refers to the development of the structures from the third to eighth week that give rise to the future head and neck.They consist of three layers, the ectoderm, mesoderm and endoderm, which form the mesenchyme (derived form the lateral plate mesoderm and paraxial mesoderm), neural crest and neural placodes (from the ectoderm). [1]
The cervical sinus is a structure formed during embryonic development.It is a deep depression found on each side of the neck.It is formed as the second pharyngeal arch (hyoid arch) grows faster than the other pharyngeal arches, so they become covered.
Human embryo from thirty-one to thirty-four days Under surface of the head of a human embryo about twenty-nine days old. The head and neck of a human embryo thirty-two days old, seen from the ventral surface.
At the beginning of the ninth week, the embryo is termed a fetus (spelled "foetus" in British English). In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs. Human embryology is the study of this development during the first eight weeks after fertilization.
These project forward from the back of the embryo toward the front of the face and neck. Each arch develops its own artery, nerve that controls a distinct muscle group, and skeletal tissue. The arches are numbered from 1 to 6, with 1 being the arch closest to the head of the embryo, and arch 5 existing only transiently. [7]
The intermaxillary segment in an embryo is a mass of tissue formed by the merging of tissues in the vicinity of the nose.It is essential for human survival. It is primordial, since in the further development of the embryo this particular mass no longer appears, but parts of it remain in "the intermaxillary portion of the upper jaw, the portion of the upper lip, and the primary palate".
The epaxial muscle mass loses its segmental character to form the extensor muscles of the neck and trunk of mammals. In fishes, salamanders, caecilians, and reptiles, the body musculature remains segmented as in the embryo, though it often becomes folded and overlapping, with epaxial and hypaxial masses divided into several distinct muscle groups.
The third pouch possesses dorsal and ventral wings. Derivatives of the dorsal wings include the inferior parathyroid glands, while the ventral wings fuse to form the cytoreticular cells of the thymus.