Choana

Choana, also known as the posterior nasal aperture, is a small opening located at the back of the nasal cavity. It serves as a passageway for air to travel between the nasal cavity and the pharynx, which is the cavity located behind the nasal cavity and above the larynx.

Structure

The choana is located at the posterior end of the nasal cavity, and is bordered by several important structures. Superiorly, it is bordered by the sphenoid sinus and the vomer, which is a thin, flat bone that separates the nasal cavities. Inferiorly, it is bordered by the soft palate, which is a muscular structure that helps to separate the nasal cavity from the oral cavity. Laterally, it is bordered by the palatine processes of the maxilla, which are bony protuberances that form the upper jaw.

The choana is composed of a thin, mucous membrane that is lined with cilia, which are tiny hair-like structures that help to move mucus and trapped particles out of the nasal cavity. The choana is also lined with numerous blood vessels and nerves, which help to provide nutrients and innervation to the surrounding tissues.

Location

As mentioned, the choana is located at the posterior end of the nasal cavity, and is situated between the nasal cavity and the pharynx. It can be easily seen when looking up into the nasal cavity through the nostrils, and is located just above the soft palate.

Function

The primary function of the choana is to serve as a passageway for air to travel between the nasal cavity and the pharynx. When we breathe in through our nose, the air passes through the nostrils and into the nasal cavity, where it is warmed, humidified, and filtered by the mucous membranes and cilia. From there, the air passes through the choana and into the pharynx, where it continues on its journey down into the trachea and lungs.

In addition to its respiratory function, the choana also plays a role in the sense of smell. The olfactory nerves, which are responsible for our sense of smell, pass through the choana on their way to the olfactory bulbs in the brain.

Clinical Significance

There are several conditions that can affect the choana and cause problems with respiration and/or the sense of smell. Some common examples include:

• Nasal polyps: These are benign growths that can develop in the nasal cavity, including in the area of the choana. Nasal polyps can block the choana and cause difficulty breathing through the nose.
• Deviated septum: The septum is the bony and cartilaginous structure that separates the nasal cavity into left and right halves. A deviated septum occurs when the septum is crooked or displaced, which can cause one side of the nasal cavity to be smaller than the other. This can lead to difficulty breathing through the affected nostril, and may also cause the choana to be partially or completely blocked.
• Allergic rhinitis: This is a condition characterized by inflammation of the nasal mucous membranes in response to allergens, such as pollen or dust. Allergic rhinitis can cause swelling and congestion in the nasal cavity, which can block the choana and make it difficult to breathe through the nose.
• Sinusitis: This is an inflammation of the sinuses, which are the air-filled spaces located within the bones of the face. Sinusitis can cause swelling and congestion in the nasal cavity, which can block the choana and make it difficult to breathe through the nose. It can also cause headaches, facial pain, and a loss of sense of smell.
• Choanal atresia: This is a rare congenital condition in which the choana is partially or completely blocked. Choanal atresia can cause respiratory distress in newborns and can be life-threatening if left untreated. It is usually diagnosed shortly after birth and can be treated with surgery to widen the choana and create a passageway for air.
• Choanal stenosis: This is a condition in which the choana becomes narrowed or partially blocked. Choanal stenosis can cause difficulty breathing through the nose and a loss of sense of smell. It can be caused by a variety of factors, including inflammation, scarring, and tumor growth. Treatment may involve medications, nasal irrigation, or surgery to widen the choana.