BIO380H5 Lecture Notes - Lecture 21: Stomodeum, Yolk Sac, Chondrocranium
Document Summary
Bio 380 lecture 21 head and neck. The brain is protected by the skull. The endoderm is a tube located underneath the notochord: on both sides, there are the mesodermal cells, at the anterior part of the endoderm, there is the stomodeum which is the ectoderm and endoderm connected without mesoderm. They push all mesenchymal cells surrounding them to the side; they form bulges. The first arch called the mandibular arch. Above it is the maxillary process (not an arch) The pharyngeal (branchial) groove are the grooves between the arches; there are three grooves. Each pharyngeal groove and arch provides a different structure. By the end of the third month of development there are several aortic arches which eventually fuse into one: there is no aortic arch number 5, due to the odd way they are numbered (1,2,3,4,6) By the end of the fourth week of development: the stomodeum is closed.
