National Board Dental Hygiene Examination (NBDHE) Dental Hygienist Practice Test

When the globular process fails to fuse with the maxillary process during the first trimester of pregnancy, it results in a cleft lip. The globular process is a key structure in the embryonic development of the face, specifically in the formation of the upper lip. The maxillary processes are paired structures that contribute to the sides of the upper lip and the hard palate. If these structures do not properly fuse, it creates a gap, which is clinically recognized as a cleft lip.

Cleft lip can manifest as a complete or incomplete fissure that may extend from the lip to the nose, impacting both cosmetic appearance and potentially feeding or speech development later in life. This condition typically occurs during the critical period of facial development, which is why the timing in the first trimester is crucial for this differentiation.

In contrast, conditions such as Down syndrome, cleft palate, and spina bifida have different embryological causes and developmental mechanisms. For instance, cleft palate involves the failure of palatine processes of the maxilla to fuse, which is distinct from the fusion issues responsible for cleft lip. Understanding these nuances is vital for dental hygienists and healthcare professionals working with affected populations.