How are organs structured in terms of tissues?

[misheru]

Hello, this is my first time posting in the forums, and I wanted to know if there were some posters here who could help me with an anatomy concept that's driving me nuts. In my anatomy/physiology class, we are currently learning the different types of layers. I understand the classification of layers, how to name them, etc. What is blowing my mind is the following:

 

If simple epithelium is made up of only ONE layer of cells, how in the world could it make up the structures in the body which are, by logic, made up of thousands of cells? Even stratified epithelium that I find pictures of on google and such show that the difference between the apicl surface and the basement membrane is between 5 to 10 layers of cells. Last time I checked, the stomach lining was not 10 cells thick.

 

I'm sure I'm missing something here, but I can't figure out what. I think it has to do with my difficulty of picturing tissues as 3-Dimensional with 2-D pictures. My view of how I THINK the stomach is structured is in the attached file. It is a sectional view of the stomach lining.

 

Please, let me know if the way I picture it is correct, or if not, how it is actually structured. I have an exam on monday, and although I don't need to know this for it, it would help me understand the concept of tissues greatly.

[immortal]

I guess your perception of it is wrong or you're missing something.

 

 

 

This picture shows the lining of the alimentary canal and it is very much similar to how the lining is done in stomach and it might give you some insights. The mucous membrane which is the innermost lining of the stomach is where you'll find the different epithelium cell types and it has to be a single layer of cells since it is basically used for absorption and secretion and hence the reason they are used for lining internally and you won't find them on places where there are too much stress, if you find them then they're dead like on your skin.

 

 

 

 

This image shows how the peritoneum which has two layers called the parietal(thick dark lines) and visceral(slightly shaded region) is covering the various internal organs from the side view. In between these two layers a small amount of serous fluid exists.

 

 

In Anatomy it is always important to understand the terms like posterior, anterior etc Anatomical terminalogy .

[Josh M]

The mucous membrane which is the innermost lining of the stomach is where you'll find the different epithelium cell types and it has to be a single layer of cells since it is basically used for absorption and secretion and hence the reason they are used for lining internally and you won't find them on places where there are too much stress, if you find them then they're dead like on your skin.

Thing is.... I was taught that "secretion" is a function of stratified squamous epithelium, stratified cuboidal epithelium and stratified columnar epithelium, all of which have more than a single layer of cells.

 

If simple epithelium is made up of only ONE layer of cells, how in the world could it make up the structures in the body which are, by logic, made up of thousands of cells?

If you look at how kidneys work, you'll notice they don't shove everything through a sheet-like filter, they run it through ducts. Maybe if they had to shove it through the filter, they'd break the single layer of cuboidal epithelium that absorbs and secretes the materials they deal with. But instead they just run it through, and if they miss something, they catch it the next time it comes around. That's how and why they must work so steadily and slowly (actually there are a few dozen reasons, but that'll come together later). That's how blood vessels work too. Everything they secrete and absorb runs through mesothelium, a single layer of squamous epithelium, which sounds impossible until you consider that this single layer lines the entire surface area of the blood vessels, which, as you'll recall, has close access to every cell in the body.

 

I think the one common element you'll find while studying simple epithelium is that it's never (okay, there's probably an exception somewhere, but it's undoubtably remote) used for secretory or absorptive tasks that require sudden results. It's too delicate. You won't find it secreting hormones or anything - it does slow, steady work, like lubricating serous membranes to reduce friction from muscle movement (in the case of mesothelium).

 

I would also keep in mind (as immortal demonstrated) that although simple epithelium is, in itself, only a single layer of cells, there's usually several layers of something else on each side of it.

[immortal]

Thing is.... I was taught that "secretion" is a function of stratified squamous epithelium, stratified cuboidal epithelium and stratified columnar epithelium, all of which have more than a single layer of cells.

 

Oh yes stratified epithelia is an exception, I'm still learning.

[Josh M]

Haha makes three of us.

[Ahsan Iqbal]

If simple epithelium is made up of only ONE layer of cells, how in the world could it make up the structures in the body which are, by logic, made up of thousands of cells? Even stratified epithelium that I find pictures of on google and such show that the difference between the apicl surface and the basement membrane is between 5 to 10 layers of cells. Last time I checked, the stomach lining was not 10 cells thick.

I didn't get exactly what you meant in this paragraph. What I understood from the quoted paragraph is that you are finding it difficult to understand how these thin epithelia make such complex structures as the stomach. If this is the problem then the answer is quite simple. Consider the case of stomach. When you go from inside to outside, you encounter the following layers.

• Mucosa
• Submucosa
• Muscularis Externa
• Serosa

Now where comes the epithelium in all these? The answer is that epithelium is the first layer (from inside) of mucosa. Beneath the epithelium is lamina propria and then muscularis mucosae. So the purpose of all this was to tell you that epithelium is just a small component of the structure of stomach. The bulk of the wall is formed connective tissue and muscle. So those hundreds of thousands of cells are not all epithelial cells. In fact very few of them are epithelial. Most of them are either connective tissue cells or muscle cells.

 

I hope this helps. But if I have explained the wrong thing to you, please tell me what exactly you don't understand so that I may help you.

[kitkat]

Recently Science Daily had an article that said that organ formation is done by bioelectrical code - voltage plus ion flow