Sunday, April 23, 2017

The Basics : Lateral wall of Nasal cavity

Hey Awesomites
In this post, I will be talking about the anatomical structures in the lateral wall of the nasal cavity. 

Three prominent elevations (or conchae) mark the lateral wall of nose :
- Superior concha ( ethmoturbinal )
- Middle concha ( ethmoturbinal )
- Inferior concha ( separate bone )


These conchae ( or turbinates ) are basically thin, scroll - like bony projections covered by mucous membrane. They narrow the nasal passages and create a large surface area, forcing inhaled air to pass around and over them. This arrangement aids in warming and moistening of the inhaled air.


The spaces around the conchae are called the meatuses:
- Inferior meatus - below and lateral to the inferior concha
- Middle meatus - below and lateral to the middle concha
- Superior meatus - below and lateral to the superior concha.

 The space above the superior concha is the Spheno - ethmoidal recess.


The four nasal sinuses - the Frontal, Ethmoidal, Sphenoidal and the Maxillary, are continuous with the nasal cavity. The openings ( or ostia ) through which the sinuses drain are obscured by the overlying conchae. So now let's remove the conchae and see the routes of drainage of these sinuses:




1. Frontal sinus - drains through a Funnel - like tunnel ( or infundibulum ) into the upper end of the Hiatus semilunaris ( a shallow depression in the lateral wall of middle meatus ).

2. Ethmoidal sinus / Ethmoidal air cells (EAC) - a group of cells in the superior aspect of nasal cavity that drain in at least three locations:
- The Anterior ethmoidal cells drain anterior to the Hiatus semilunaris. Agger Nasi cells are the anteriormost. ( Remember the A )
- The Middle ethmoidal cells drain into one or more openings in a bulging structure above the HS - the Ethmoidal Bulla. ( largest cells, in the middle meatus )
- Posterior air cells drain via one or more openings into the posterior aspect of superior meatus. Onodi cells are posterior ethmoidal cells, very close to the Optic nerve. ( Remember the O )

3. Sphenoidal air sinus - drains by one or two openings into the spheno - ethmoidal sinus.

4. The Maxillary sinus drains into the middle meatus to an opening in inferior part of the HS. The drainage opening is usually located at the top of the sinus, so this sinus has to be filled completely before it can be drained. 


5. Opening for the Nasolacrimal duct is situated in the inferior meatus ( guarded by Hasner's valve ) through which overflow of tears from the eye into the nasal cavity and its mixture with the mucus secretions in the nose takes place and is responsible for running nose when we laugh hard or cry.


SKELETON of the lateral wall of nasal cavity:-


- The Ethmoid bone forms most of the part of the lateral wall, including the upper and middle conchae.
- The lower part of the lateral wall is formed by the vertical process of palatine bone and the body of Maxilla.
- Anteriorly, the lateral wall is formed by the Nasal bone, and the lateral nasal and alar cartilages in addition to various small unnamed cartilages.
( Note that the Inferior concha is a separate bone )


Thats all
Hope this helped :)

- Jaskunwar Singh

2 comments:

  1. Thanks for such a wonderful notes.
    These basics are very useful for us which we easily tend to forget!

    ReplyDelete
    Replies
    1. Your most welcome, Madhu. Glad to know that :)

      Delete

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