Re: Why do humans have two nostrils?

Dear John,

Your questions are best answered in the order that you've asked them.

1. Is there any particular reason/advantage in having two nostrils? 

No, there is no particular advantage to having two nostrils (if we define 
the word as specifically as we can and mean two "openings" into the nasal 
cavity.

2. What would happen if someone only had one nostril? 

If that nostril served both chambers of the nasal cavity, nothing untoward 
would happen.

3. Why do humans have two nostrils?

Most animals, including humans, are bilaterally symmetrical. This means 
that the right and left sides are mirror images of one another. Thus both 
sides develop somewhat independently of each other. Having said that I have 
to emphasize the word "somewhat," since there is a great deal of 
interrelationship, interaction, and communication between the two sides 
for normal development to occur. Thus, as the face develops, two nasal 
placodes (thickenings of the frontal process) develop. These begin to 
submerge and as they do, each placode results in the formation of a nasal 
chamber, and the region surrounding each placode forms a horseshoe-shaped 
thickening, known as  the nasal process. Each nasal process is subdivided 
into a lateral and a medial nasal process, which partially surround the 
opening into nasal chamber. Since it is a horseshoe-shaped structure, it 
will require a closure at its open end and that closure results from the 
fusion of the lateral and medial nasal processes with the developing 
maxillary process.

I hope this helps.

Leslie P. Gartner, Ph.D.
Associate Professor of Anatomy
Dental School
University of Maryland
Baltimore, MD
  

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check out the answer at 
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