The mesenchymal cells that surround the crypts arise from materials of second pharyngeal arch
. Developmental abnormality leading to formation of cartilage and bone within tonsil can result in osteo-cartilaginous choristoma of tonsil.
However, hesitation or distortion of the fusion of the cartilaginous tissue between the fourth and the sixth pharyngeal arches
may lead to the foramen to remain open (2, 3).
Pharyngula stage starts after 40th h till 88th h after post fertilization (2-4 dpf) characterized with rudiment pharyngeal arches
, which were present, but difcult to differentiate independently at earlier period.
The teratogenecity of RA is manifested primarily by arresting the migration of cranial neural crest cells (CNCC), to their destined tissues, including to the pharyngeal arches
. Since CNCC contributes to thymus organogenesis7, it is one of the constant targets of retinoic embryopathy8.
These regions arise from proliferation of mesenchymal tissue of 2nd, 3rd and 4th pairs of pharyngeal arches
. Following formation of tuberculum impar, two lateral swellings appear at both sides of first pharyngeal (branchial) arch, which extend into centre of primary oral cavity.
Shellcrackers have a set of crushers (pharyngeal arches
) in their throats with molar-like teeth specifically evolved for eating snails and other freshwater mollusks.
The posterior one third of the tongue arises from the hypobranchial eminence, which is made up of mesoderm of the second, third and a portion of the fourth pharyngeal arches
. Congenital dermoid cysts arise from epithelial rests trapped during midline fusion of these branchial arches whereas acquired dermoid cyst arise from epithelium implanted during trauma and they occur at the sites away from midline.