The Digestive System

How Does Food Get to All My Cells???

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Why the Digestive System?

• Every cell of your body needs specific materials (like nutrients and oxygen) so they can do the job they are made to do.

Take this lad for example. In his nose there are cells that need nutrients.

He just can’t hold a Double Cheese Burger up to his nose and expect those cells to eat!

This burger needs to be broken down to the molecular level before those nose cells can use it.

And that journey from burger to molecules begins in your mouth.

Digestion begins in your mouth. Your teeth starts breaking up the food into smaller particles while your tongue pushes the food around making sure it gets to the teeth. This is where mechanical digestion begins.

1. The Mouth

While the food is getting broken down into smaller pieces it gets mixed with saliva. This saliva contains chemicals that start to break the food down chemically.

Here are the salivary glands shown in yellow.

Don’ t believe it? Try This – 1.Get an unsalted cracker (unsalted

works better)2.Chew it up but don’t swallow it – yet3.Let it sit in your mouth for about a

minute and describe the change in taste.

What happens is this –

The starch in the cracker starts to be chemically broken down by the enzymes in the saliva. Starch is nothing more that glucose (sugar) molecules joined together.

So, as the cracker sits in your mouth you start to taste a sweet taste. This is also where chemical digestion begins.

So, in review, two types of digestion begins in the mouth:

Mechanical digestion – the food is physically broken up by the teeth and tongue.

Chemical digestion – the food is chemically broken down by enzymes in the saliva.

Now, the food is still a long way off in getting to the cells in the nose. The next place the food travels to is the esophagus. The esophagus is a 10-inch tube that carries the food to the stomach.

2. The Esophagus

Before we get to far down the esophagus let’s mention the epiglottis. It’s found at the top of the esophagus. It’s job is to keep food out of the lungs. Each time you swallow the epiglottis covers the windpipe (trachea).

From a sheep

Back of tongue

Epiglottis

Esophagus(cut vertically)

When you speak the epiglottis is up. When you swallow the epiglottis is down.

What’s this mean??

When you eat and talk you increase your chances of choking by food going down your windpipe.

Cancer masses in the esophagus

What does it look like inside?

One treatment type for this blockage

Here is an actual photograph of the flexible stent placed in the esophagus.

Once the food gets to the stomach the stomach uses chemicals to try to make the food tinier. These chemicals are called gastric juices and the include hydrochloric acid and enzymes (chemicals that continue to break down food).

3. The Stomach

The food is moved around in the stomach and mixed with the chemicals for about 3 or 4 hours. When it is done in the stomach, the food is now a cream-like liquid call chyme.

But the food is still not small enough to get into our blood stream and still must be broken down smaller. That comes up next.

Heartburn / Ulcers

The stomach also produces mucus which lines the stomach and prevents the acids from eating through it. If that mucus isn’t there then ulcers occur.

The chyme now leaves the stomach and enters into the first few inches of small intestine called the duodenum. Here, chemicals are added to the chyme from a variety of organs:

Liver/Gall Bladder- At this point, our food is hit with more chemicals. The liver makes a chemical called bile which is stored in the gall bladder. Bile breaks down the fat (from milk, butter, cheeses) into tiny droplets. This fat will supply us with much energy later.

If the bile crystallizes it will form gall stones. These stones may block the bile duct and cause pain.

Before Operation After Operation

Sometimes the gall bladder has to be removed

Pancreas- The pancreas also adds a digestive chemical as the food leaves the stomach. This digestive juice works on breaking down the carbohydrates (from breads, potatoes, etc.) and the proteins (from meats, cereals, peanut butter)

Small Intestine - The small intestine is a tube that is about 22 feet long. This is where the real digestion takes place. As the food passes through, it is mixed with the new chemicals and soon our "food" is now digested small enough to be put to use by the body.

4. The Small Intestine

Here is what the small intestine looks like on the inside. As you can see there are many layers to it.

Notice the little “bumps” on the inner layer.

Those thousands of tiny bumps are called villi. Blood vessels (capillaries) in the villi can absorb the tiny food molecules, by diffusion, and send them off to the rest of our body through the blood.

Once the food gets broken down to the molecular level and enters the bloodstream through the villi, then the blood will take that food all the way up to those cells in the nose (or anywhere else in the body) and supply them with nutrients they need.

As blood with food flows through capillaries the food goes out into the surrounding cells.

How does the food get into the cells??

Remember diffusion?????

Food molecules go from an area of high concentration (outside the cell) to an area of low concentration (inside the cell).

Diffusion refresher...

As waste products are produced by the cell they leave the cell in the very same way – by diffusion. There is a higher concentration of waste product on the inside of the cell than on the outside of the cell.

Sometimes a person may have a guest in their small intestine

The Tapeworm

In the Tokyo Parasite Museum – a 30 foot tapeworm

Minnow with excised tapeworm

This is why you should always give your dogs worm pills…….

Many years ago women took capsules with tapeworms in them to help lose weight.

The large intestine, or now commonly called the colon, is 1.5 meters in length.

5. The Large Intestine (Colon)

The function of the colon is to simply remove water from the waste before it leaves the animal’s body.

Too much water sucked out = constipation

Too little water sucked out = diarrhea

Here is what the normal colon looks like on the inside -

Cancer cells also may grow in the colon. These growths are called polyps.

Here is a colon with polyps -

Question: How can this cancer be prevented?

Answer: Nothing stops cancer but with regular checkups you can remove what has grown. If not removed it can spread.

Barium enema: A series of x-rays of the lower gastrointestinal tract. A liquid that contains barium (a silver-white metallic compound) is put into the rectum. The barium coats the lower gastrointestinal tract and x-rays are taken. This procedure is also called a lower GI series.

Barium enema procedure. The patient lies on an x-ray table. Barium liquid is put into the rectum and flows through the colon. X-rays are taken to look for abnormal areas.

Sigmoidoscopy: A procedure to look inside the rectum and sigmoid (lower) colon for polyps, abnormal areas, or cancer. A sigmoidoscope is inserted through the rectum into the sigmoid colon. A sigmoidoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.

Colonoscopy: A procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A colonoscope is inserted through the rectum into the colon. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.

Possible signs of colon cancer include:

• A change in bowel habits. • Blood (either bright red or very dark) in the stool. • Diarrhea, constipation, or feeling that the bowel does not empty completely. • Stools that are narrower than usual. • Frequent gas pains, bloating, fullness, or cramps. • Weight loss for no known reason. • Feeling very tired. • Vomiting.

What can be done if the growth is severe -

6. The Final Step

After the undigested mass has the water taken from it the last step is removal from the body.

I think you can figure it out the rest of it from here…..

Digestive System Animation