A fifth pharyngeal arch artery does not exist in rat

Area of Science:

• Developmental biology
• Embryology
• Vascular anatomy

Background:

• Pharyngeal arch arteries are crucial for embryonic head and neck development.
• Understanding their formation is key to identifying congenital anomalies.

Purpose of the Study:

• To investigate the developmental process of caudal pharyngeal arch arteries in rat embryos.
• To clarify the existence and role of the fifth pharyngeal arch artery.

Main Methods:

• Utilized perfused rat embryos from embryonic day 12 1/2 to 13 3/4.
• Employed semithin serial sections for detailed morphological analysis.
• Generated computer-aided 3-dimensional reconstructions for spatial understanding.

Main Results:

• The fourth pharyngeal arch artery was present by embryonic day 12 1/2.
• The sixth pharyngeal arch artery formed from vascular sprouts by embryonic day 13 1/4.
• A vascular plexus, not a distinct fifth artery, was observed between the fourth and sixth arteries, originating from the fourth arch artery and later the sixth, draining to the venous system.

Conclusions:

• The fifth pharyngeal arch artery does not develop as a distinct vessel in rats.
• A transient vascular plexus plays a role in connecting the fourth and sixth pharyngeal arch arteries.
• This plexus undergoes involution and its branches to the lower cervical sinus become prominent.