According to my mathematics, the duodenum accounts for 5% of the length of the small intestine

So the Jejunum + Ileum is 95% - so almost all of the small intestine

We won't look at the jejunum and ileum separately, we will just consider them as 'the small intestine' from here.

The duodenum also does absorption. The duodenum has villi and microvilli and brush-boarder enzymes. The duodenum has capillaries and lacteals inside its villi. But, there was so much happening there, that I thought we'd leave it for this bit.

The small intestine is called small because the pipe is narrow. I would have called it the long intestine. The pipe has a width of about 1.5 - 2cm. About the same width as your finger

This increased surface area increases the area for the nutrients to be absorbed

It is hard to calculate the exact surface area of the small intestine. Depending on the source calculations, the surface area ranges from one side of a badminton court, to an entire tennis court. The point being that the surface area is very large.

The chyme that passes through the small intestine has a consistency much like 'cup-a-soup'. So by increasing the surface area, even if it is just half a badminton court. then it is like blending and pureeing your dinner until it is drinkable, and then using a paint brush and having to coat the entire half badminton court, every corner of it, with your pureed dinner

In the clip called normal small bowel (American for Small Intestine) you can see all the villi

We keep zooming in we see that the fuzziness continues

It is so fuzzy that you can only see what is causing the fuzziness by zooming in with an electron microscope

It is so fuzzy, that it kind of resembles the bristles on a brush.

Because of this, the lining is also called the 'brush-border'

The bristles on this brush border are called microvilli

Arteries take blood Away from the heart

Veins return, or 'veturn' (say it like Count Dracula) the blood to the heart

Arteries are like the top of a tree, splitting into smaller and smaller branches and twigs.

Veins are like the roots of a tree, starting off tiny, then joining into larger and larger roots

But in this weird tree, the roots touch the twigs. This junction is called the Capillaries

Capillaries are absolutely everywhere in the human body

Capillaries are where the gases move and the nutrients move

Capillaries are tiny, they are slightly narrower than a red blood cell is wide, causing the red blood cells to change from a donut shape into more of a parachute shape (this is actually the reason for their donut shape, as they become a parachute their diameter reduces)

Often you'll hear blood vessels and roads being compared.

This is why you'll often here the phrases 'the major artery away from the city' and all of the 'arterial routes' out of the city.

An analogy would be buying a 'My Food Bag"

Arteries and Veins = Motorways away and returning to the CBD where the My food bag HQ is

Arterioles and Venioles = main streets

Capillaries = narrow one way side streets

Exchange = The Courier guy slowing down his van, but not stopping, and throwing your Food bag out his window at your house, while at the same time you pick up rubbish and throw it at him, getting it through the open van window

Watch this clip, it is really good!!

The small intestine is supplied with oxygen rich blood from the Mesenteric Arteries. These branch becoming smaller and smaller until finally you have blood vessels that are so small they can only fit one blood cell at a time. These are the Capillaries

Here gas exchange and nutrient exchange occurs

The Oxygen in the leaves the capillaries and moves into the cells of the villi to keep them alive. Carbon Dioxide moves from the cells of the villi into the capillary to the be moved ultimately to the lungs

The nutrients move into the blood vessels. But only the water soluble ones; sugars and bits of proteins!

Capillaries in the Villi take up the Sugars and Amino acids (and peptides) that are absorbed through the wall of the villus

Villi = plural, lots of little fingers

Villus = singular, one finger

The Capillaries then take these nutrients to the liver for processing before returning to the heart.

To get to the Liver the capillaries join into veins that get bigger and bigger as more and more veins join together until they finally get to the highway, the big main vein going from the intestines to the liver, the Hepatic Portal Vein

So it goes:

Arteries - Arterioles (the little artery branches) - capillaries - venioles (little vein branches) - veins

With the digestive system, it goes:

Mesenteric arteries - arterioles - capillaries - venioles - veins

These veins then collect in the Hepatic Portal Vein

Hepatic means liver

The Hepatic Portal Vein takes all the blood from the intestines to the liver for processing

Inflammation is a major cause of disability and death.

The immune system can damage healthy tissue as collateral damage when it is at war with something.

The immune system can be looked at like the USA Military - especially their 'strategic missile strikes' - highly effective at removing enemies. However, also takes out allies.

This happens with Cardiovascular disease

This also happens with Coeliac

The persons immune system is targeting an enemy

Unfortunately the enemy looks like gluten

So, the immune system targets gluten which is made in Wheat

Unfortunately for suffers. Most of our Flour, and thus almost all products made with flour (cakes, bread, muffins, pasta) contain gluten.

They can switch to gluten free meal for their starch - like potatoes and rice.

However flour products are everywhere, imaging not being able to eat any bread?

They don't know that they have Coeliac disease until it has progressed to the point where they have symptoms:

1. Sore tummy after they have eaten flour products - due to inflammation in the intestines

2. Watery feces - due to the inflammation

3. Weight loss and low iron - why would this be?

Overtime the inflammation damages the villi

The villi get smaller. Getting smaller is called 'atrophy'

Because the villi are smaller there is less surface area for absorption of nutrients.

Thus, less nutrients are absorbed

The suffers run the risk of lacking certain vital nutrients.

These include vitamins and minerals such as Iron and Calcium

The chronic inflammation in the small intestine can cause extreme damage including ulceration so it needs to be checked and treated

Have a look at the comparison clip below. This shows an Endoscope moving through the small intestine of a person without celiacs on one side and on the other side, the intestine of a person with ceoliac disease.