DEVELOPMENTAL TIMELINE
Occurs at the end of Week 1 and involves attachment to the endometrium.
What is implantation?
This germ layer forms enamel.
What is ectoderm?
Cleft lip results from failure of fusion of these two processes.
What are maxillary and medial nasal processes?
This forms a cone-shaped mass that occupies most of the developing ramus.
What is condylar cartilage?
The arches that appear as bulges on the lateral aspect of the embryo.
What are branchial or pharyngeal arches?
The primitive streak appears during this week.
What is week 3?
This cell population forms dentin and pulp.
What are neural crest cells?
The secondary palate develops from these structures.
What are palatal shelves of the maxillary processes?
This cartilage serves as a template for mandibular development but does not directly become the mandible.
What is Meckel’s cartilage?
The second pharyngeal arch is also known by this name.
What is the hyoid arch?
Neural tube closure is completed by the end of this week.
What is week 4?
Skeletal muscles originate from this layer.
What is mesoderm?
This arch contributes to the mandible.
What is the first pharyngeal arch?
The mandible develops by this type of ossification.
What is intramembranous ossification?
Muscles of facial expression develop from this arch.
What is the second pharyngeal arch?
This period (Weeks 3–8) is the most critical for organ formation.
What is the embryonic period?
The thyroid gland is derived from this germ layer.
What is endoderm?
This structure guides midline facial development.
What is the frontonasal process?
The maxilla forms from this embryonic prominence.
What is the maxillary process?
Failure of proper development of the first arch may result in this condition characterized by mandibular hypoplasia.
What is Treacher Collins syndrome?
A solid ball of cells resulting from division of a fertilized ovum.
What is a morula?
During the 8th day - 2nd week, the embryo develops into a 2-layered disk.
What is bilaminar germ disk?
The failure of central fusion of mandibular prominences.
What is gnathochisis?
This mechanism explains how the mandible forms lateral to Meckel’s cartilage without replacing it.
What is intramembranous ossification around Meckel’s cartilage?
This embryonic cell population migrates into the pharyngeal arches and contributes to craniofacial skeleton formation.
What are neural crest cells?