The body’s relationship with the food we eat, water we drink, air we breathe, even with our reproduction is controlled by internal cellular layers that are cell, hormone, enzyme, blood, lymph and nerve rich. Mucous membranes are found in the lungs, mouth, nose, eyelids, trachea, ureters, urethra, bladder, vagina, oesophagus, stomach and intestine.
The layers in the gut are arranged in to mucosa, submucosa, muscularis (muscle layer), and finally serosa, a protective, fluid secreting membrane. These layers, together with the digestive organs, and signalling from the brain, coordinate the process of digestion. The very inner layer of the tube provides an essential barrier from toxins, undigested food and bacteria from getting anywhere near our blood and lymph circulation and nervous system. In this article we look at how absorption and signalling should occur and how arsenic can put a big spanner in the works.
The jejunum and ileum absorb most nutrients we ingest. They also continue the digestive processes started in the stomach and duodenum. The jejunum, a tube of approximately 8 feet long, is attached to the duodenum in the upper section of the small intestine. It is carefully designed to maximise absorption of nutrients in to the blood stream and lymph vessels and is the primary absorption site of the gut. The ileum sits in the lower part of the small intestine and opens in to the large intestine (colon) through the ileocecal valve. Vitamin B12 and bile acids are absorbed through the Ileum. The valve regulates the speed food waste removal from the small intestine. It is transferred in to the colon where excess water is absorbed, compacting and solidifting waste to await explusion in the form of faeces. The ileum is approximately 11.5 feet long in adults.
When the jejunum is reduced in length as a result of surgery, the ileum can adapt to absorb nutrients in the same way as the jejunum, however this does not occur the other way around if the ileum is reduced in length.
As we discovered in the last article, arsenic in food can block enzymes and chemicals required to break down protein, starches and fats in the mouth, stomach and duodenum. It selectively deactivates enzymes, receptors, hormones, immunological proteins and nuclear receptors in cells by attaching to available disulphide bridges. It can also interfere with the cellular respiration of all cells by displacing phosphate with arsenate and can even switch genetic controls on or off by displacing zinc.
We are going to unpick how arsenic can throw the digestive system in to complete disarray. Where a figure appears in brackets after a protein name eg. (11 DSB), this refers to the number of disulphide bridges it contains, targets for arsenic adhesion. All disulphide bridge data and protein functions are crosschecked with Uniprot.org.
Blood, Lymph and Nerves
The surface of the mucosa is made up of finger-like protrusions called villi. Each has an arterial capillary supply (arteriole) and a veinous capillary (venule) within its submucosa. The arterial capillaries keep the gut wall supplied with oxygen, and the veins absorb nutrients, which are then carried away to the liver to metabolise through the hepatic portal vein. Lacteal vessels are microscopic lymphatic vessels. They absorb some of the digested fats in to the lymph system. They empty in to larger lacteals, then in to the lymph nodes in the mesentary.
The aorta, vena cava, hepatic vein, and lymphatic sac (cisterna chyli) and splanchnic nerve all run along the spine and are connected, through the mesentary, to the gut. This is how close our blood, lymph and nervous systems are to the food we eat.
If we were to pull all of the digestive organs and small and large intestine out of the abdominal cavity, we would find they are all attached via the mesentary in a fan type arrangement across the whole inferior (back) abdomen wall. All structures of the digestive system are dependent on their connection to the body by the mesentary.
We can see the blood supply as it is carried through the mesentery in the diagram above. The lymph nodes are wrapped around each branch of arterial and veinous supply, acting as sentries to foreign material leaking in to vessels, before they make it in to circulation or in to the central nervous system.