Metaplasia

[rose.82]

Hi,

Please tell me am I right?
In Baret esophagitis we have squamous metaplasia that means squamous cell change to columnar cell(cause: gastric acid)
In smoking we have squamous metaplasia in bronchial epithelium that means columnar cell change to squamous cell.
In normal people in broncioles we have simple squamous alveolar epithelium .
I'm confused.
Thanks for answers.

[Dr. X]

In Baret esophagitis we have squamous metaplasia that means squamous cell change to columnar cell(cause: gastric acid)
In smoking we have squamous metaplasia in bronchial epithelium that means columnar cell change to squamous cell.
In normal people in broncioles we have simple squamous alveolar epithelium

few changes..

GI - Barrett's esophagus --> glandular metaplasia (sqamous to columnar)

Lungs - Smoking --> sqamous metaplaia (pseudostratified columnar to squamous)

Lungs - Normal --> In bronchioles we got pseduostratified, ciliated columnar.
Starting from respiratory mucosa (after vesitbule) upto bronchioles, we got pseudostratified columnar.. except few things in between:
Ventral epiglottis, oropharynx, vocal box - stratified sq. nonker. epithelium.

[IMG SURVIVOR]

Dr X
You are correct

[Ella]

Ok metaplasia is basically when one cell type replaces another (normally the new cell type is better able to stand the pathological environment when compared to the old cell that would have normally been present). The name of the metaplasia (ie. squamous metaplasia, columnar metaplasia) refers to the NEW cell that is present.

In Barretts esophagus - there is columnar metaplasia. Best way to understand this is that in normal people there is non ker. Squamous epithelium in the esophagus and columnar epithelium in the stomach. When there is reflux as seen in Barretts, the pH of the esophagus becomes more acidic and thus creates a pathological environment. So the cells from the gastric epithelium (columnar cells) start growing upwards into the esophagus and the esophagus squamous cell undergo metaplasia. These new columnar cells are better suited for the acid environment.
Remember also that Barretts leads to adeno-carcinoma. Usually esophageal cancers are squamous cell carcinoma (makes sense because the esophagus has squamous cells) .....but with Barretts, due to the metaplasia, it leads to adeno-carcinoma.

In smokers, there is squamous metaplasia. Meaning that the new cells are squamous cells. Originally in a normal person the bronchioles have columnar to simple cuboidal cells. Toxins in the Cig smoke cause these cells to under metaplasia and convert them to squamous cells - leading to squamous cell carcinoma.

Also remember in smokers you can also see adeno-carcinoma, and small cell carcinoma.

Adenocarcinoma - Peripherally, very common
Squamous cell - centrally
Small cell - centrally and worst prognosis.

Lastly, here is the normal cell types in the resp system:

Nasopharynx - pseudo stratified ciliated columnar
larynx - pseudo stratified ciliated columnar
Trachea and bronchi - pseudo stratified ciliated columnar
Primary bronchioles - simple ciliated columnar to simple cuboidal
Terminal bronchioles - simple cuboidal
Resp bronchioles - simple cuboidal
Alveolar ducts - simple squamous
Alveoli - Simple squamous.

[Ella]

Hmm I guess Dr. X and IMG ...you guys posted as I was typing out my response...

I have a question - doens't broncioles have columnar/cuboidal?

[Ella]

oops n/m - i thought I read something different in your post. Ignore my last question!

Only difference is in the pseudo stratified vs. simple. (minor thing i know!)

[Dr. X]

ella.. while mine n img's post are brief, yours was very descriptive and more specific. one of the reasons why i choose to come here is so that i learn from my own posts and see how i understand things. in a similar context, you have done a good job.