The Intricacies of the Human Nose
The human nose is an intricate organ that performs several crucial roles. It conditions the air we breathe before it reaches the lungs by filtering particles and adjusting the air temperature. The nose also facilitates a smooth airflow which activates receptors to maintain the patency of the upper airways. Additionally, it fulfills an essential role in the immune system.
The Nasal Cycle
Throughout the day, the nostrils undergo a process of alternating contraction and expansion known as the nasal cycle. This cycle, which switches every two to four hours, means that at any given moment, the majority of air is flowing in and out of one nostril, while the other nostril has a significantly reduced airflow. The regulation of this process is controlled automatically by the swelling and shrinking of the nasal tissue.
Why Do Nostrils Alternate?
There are two primary reasons for the nostrils’ alternating activity. The first reason is to enhance our olfactory perception. Scents break down at varying rates based on their volatility, and certain odors are more easily discerned in the fast-moving air of the “open” nostril, while others are more detectable in the “constricted” nostril’s slower air stream. This is particularly impressive considering that a dog possesses over 100 million more olfactory receptors than a human.
The second reason is to maintain the nose’s optimal condition. The alternation of congestion allows the cilia—tiny hairs that move a layer of mucus—to rest from their filtering duties, while also preventing the nostrils from drying out. It underscores that the nose is naturally designed for respiration, whereas the mouth is intended for eating and speaking. It is important for individuals to utilize their nose for its primary purpose of breathing.
References
- Variation in nasal mucosa congestion during rest
