Only the nose knows

We all know the nose is an important organ, particularly for the sense of smell.  Within the nose of mammals is a labyrinth of bones called the turbinate bones.  These are covered in a thin layer of tissue in which there are areas with sensory centres and these communicate with sensory nerves (the olfactory nerves).  But this is not all the nose is capable of;  Here we discuss how pathology affects the biomechanics, and vice versa, within the nose…

The concha (turbinates) are scrolls of bone lined by epithelium within the nasal cavity

Concha (turbinates) are scrolls of bone lined by epithelium within the nasal cavity

The extra layers of tissue supported by the turbinates increases the surface area within the nose massively. As air is breathed in, it is warmed, humidified and filtered over the surface of these scrolls of tissue.  Breathing through the nose can be altered to change the pathway the air takes – either to increase the amount going to the lungs, or to the sensory areas of the nose for smelling (olfaction), by sniffing.

Temperature control (thermoregulation) is important when it comes to the replication of some viruses.  The cooler environment of the nose is favoured by the rhinoviruses that cause the common cold, for example.  When body temperature decreases, the immune system is less able to get rid of virus infected cells .  Some viruses prefer to replicate in cooler temperatures. ‘Cat flu’ (feline viral rhinotracheitis, caused by feline herpesvirus-1) infected cats can pass these viruses on to kittens, or to ill animals who are less able to control their body temperature.  In fact, a fever might actually be the way the body has evolved to reduce the rate of replication of some of these viruses.  Severe inflammation can destroy the turbinates, but even very mild swelling can cause the turbinate bones to breakdown and remodel.

The severe inflammation has destroyed the turbinate bones, and the nasal cavity is filled with pus.

Severe inflammation has destroyed the turbinate bones, and the nasal cavity is filled with pus (nose of a cat with ‘cat flu’).

As the air makes its journey through the nose, wind pipe, and airways of the lungs, the path splits into smaller and smaller channels.  There is mucus within the nose, windpipe and larger airways within the lungs, which act to trap particles, which are sent back up to the mouth to be swallowed, sneezed or coughed out of the respiratory system.  Toxic substances, which could potentially severely damage the little air sacs (alveoli) of the lungs, are diluted by repeatedly coming into contact with the mucus over the surface of all of the divisions.

These lungs have been severely damaged by the animal inhaling stomach acid from vomiting.

The lungs of this dog have been severely damaged inhaling stomach acid after vomiting.

The scrolled nature of the bones causes inhaled air to create a vortex, similar to the wing-tip vortex seen at the ends of wings in flight.  This causes any particles to be thrown to the outside of the vortex (centrifugal).  This is particularly fascinating; In order for the immune system to actually recognise foreign material or infectious agents, they have to come into contact with the immune cells.  The vortex brings the particles within the inspired air into contact with the cells lining the nasal cavity.

The vortex at the end of a wing is similar to the vortex created within the nose due to the scrolls of turbinate bones

The vortex at the end of a wing is similar to the vortex created within the nose by the scrolls of turbinate bones

Tumours of the nose can destroy the turbinates as they invade and grow through the nasal cavity.  This gives bacteria and viruses ample opportunity to infect the damaged nose.  Some tumours are particularly nasty and may even grow from the nose, through the skull and into the brain.

This tumour, a fibrosarcoma, has grown from the roof of the mouth into the nose, destroying the tissue as it goes.

This tumour, a fibrosarcoma, has destroyed the roof of the mouth and grown into the nose.



4 thoughts on “Only the nose knows

  1. Hi, I believe your website may be having web browser compatibility problems.
    When I look at your blog in Safari, it looks fine however, when opening in Internet Explorer, it’s got some overlapping issues.
    I just wanted to provide you with a quick heads up!
    Apart from that, fantastic site!

  2. Tasmyn says:

    Hi I have a horse who constantly has a snotty nose and often when cantering she has almost a type of a grunt could this be linked to a problem in the airways

    • It certainly sounds like the airways are involved in your horse’s problem. It would be wise to speak to your vet in order to rule out an underlying problem.

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