Choana

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Vomer and choane

Choana refers to one of the two openings found at the back of the nasal passage in vertebrates. These openings connect the nasal cavity to the throat or pharynx, playing a crucial role in the respiratory system. The term "choana" is derived from the Greek word "χοάνη," meaning "funnel." In humans and most other animals, the presence of choanae is essential for efficient breathing and proper nasal function.

Anatomy

The choanae are located at the posterior end of the nasal cavity. Each choana is bordered by several structures: the vomer bone forms its posterior border, the horizontal plate of the palatine bone constitutes the inferior border, and the sphenoid bone contributes to the superior border. The lateral walls are formed by the medial pterygoid plate of the sphenoid bone. The choanae open into the nasopharynx, the upper part of the pharynx, connecting the nasal passages to the throat.

Function

The primary function of the choanae is to facilitate the passage of air from the nasal cavities to the lungs. This airway is crucial for respiration, allowing for the inhalation of oxygen and the exhalation of carbon dioxide. The choanae also play a role in the olfactory system, as they help in directing airflow towards the olfactory receptors located in the upper part of the nasal cavity, thereby aiding in the sense of smell.

Additionally, the choanae are involved in the process of humidification, warming, and filtering of the air before it reaches the lungs. The mucous membrane lining the nasal passages and choanae traps particles and pathogens, preventing them from entering the respiratory system.

Development

During embryonic development, the choanae form as initially solid nasal plugs that eventually perforate to create a continuous airway from the nasal cavities to the nasopharynx. This process is critical for the proper development of the respiratory system. Abnormalities in choanal development can lead to congenital conditions such as Choanal atresia, where one or both choanae are blocked, leading to breathing difficulties immediately after birth.

Clinical Significance

Choanal atresia is the most common congenital disorder associated with the choanae. It can present as a unilateral or bilateral condition and requires surgical intervention to establish a patent airway. Other conditions that can affect the choanae include infections, tumors, and traumatic injuries, which can lead to symptoms such as nasal obstruction, difficulty breathing, and changes in the sense of smell.

See Also

• Nasal cavity
• Respiratory system
• Pharynx
• Choanal atresia