The choanae (singular: choana) are two openings at the back of the nasal cavity that connect the nose to the nasopharynx. They are also known as posterior nasal apertures or internal nostrils.
Location and Function
The choanae mark the posterior limit of the nasal cavity and the beginning of the nasopharynx, which is the upper part of the throat behind the nose. They are responsible for channeling air from the nasal passages into the respiratory system. The nasal cavity warms, humidifies, and filters the air before it passes through the choanae and enters the nasopharynx en route to the lungs.
Anatomy
These openings are located behind the nasal conchae (turbinates) and below the sphenoid sinus. The choanae are separated by the vomer bone. In humans and other mammals (including crocodilians and most skinks), they are distinct anatomical structures.
Clinical Significance
Blockage or obstruction of the choanae, a condition called choanal atresia, can cause breathing difficulties, particularly in newborns. This condition requires prompt diagnosis and treatment, often involving surgical correction. Other conditions, such as nasal polyps or tumors, can also obstruct the choanae.
