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February 20, 2019

How the mucus humans produce compares to house paint

Apartment in Nairobi. FILE PIC
Apartment in Nairobi. FILE PIC

The size of a typical apartment in Nairobi is about 150 metres square and shrinking. In years gone by the inside walls of a flat, as they were then called, would be painted ‘soft white’ and the ceiling ‘brilliant white’. Today in a typical apartment every room has a different colour. Has there been a revolution in paint technology to allow this? Not in terms of colour appreciation.

Across the world there is evidence that every culture have been fascinated and produced some kind of colour pigment for at least 20,000 years. Evidence from early cave paintings and later the Chinese and Egyptians show that paint was being made in significant quantities. Then and even now different colours were considered to have healing or magical properties.

Around 2500 years ago the first types of varnishes are found, an improvement on covering early colour pigments with animal fat to bind and preserve the artwork painted onto porous walls. Today’s paint is quite sophisticated in its manufacture but still serves the same purpose, a thin layer applied onto surfaces to protect and colour a surface or object. A characteristic of paint it is that it is applied wet, then dries into solid. This is quite unlike the substance used in the body that serves a similar purpose.

The outside of the body is covered with skin, which, particularly for those who refuse to listen to multinationals and apply skin lotion, can appear dry and ashen. The inside of the body, especially those surfaces that communicate with the outside world have a mucus lining. Mucus is a thinnish, clear slippery fluid produced by cells found in mucous glands.

Typical mucus is mainly water and rich in glycoproteins. The ‘glyco’ part of the glycoprotein gives mucus its lubricating qualities just like glycerine does in various skin creams and lotions. But that’s not all that is found in mucus. It is also a suspension containing enzymes and immunoglobulins. Mucus therefore not only protects through lubrication, it also protects the body by mounting a line of defence against viruses, bacteria and fungi. The availability of mucus is critical to the functioning of the respiratory, urogenital and gastrointestinal tracts. It is easy to feel and visualise when there is too much mucus in the respiratory tract, a flu or ‘homa’ being a good example, but what about when we are not producing enough?

The mouth connects to the stomach via the oesophagus, a muscular tube about 20 centimetres long. Anatomically the oesophagus runs just in front of the spinal cord, but behind the windpipe passing behind the heart then entering into the stomach through the diaphragm layer. It is lined mostly by moist pink tissue called mucosa. Its job is to carry partly chewed food from the mouth into the stomach for the first phase of digestion. Given the way some people eat you can imagine the tough job that the oesophagus has. The upper third of the oesophagus is quite muscular and under the brain’s voluntary control.

The greedy hungry eater is able to not choke because of this. Below this the oesophagus muscular control is involuntary, relying on movement similar to the way a snake moves to propel the food downwards towards the stomach. Because you cannot control this movement when something goes wrong you usually need help.

Essential to the movement of food is mucus as the lubricant. Imagine some of the dry food that people eat, for example roast maize happily sold to you by the roadside as ‘very soft’; and you can envision the role of mucus. The body has to calibrate and produce sufficient mucus for such events but not too much that it fills the entire oesophagus and you feel full all the time or worse still some of the mucus passes into the windpipe which is connected at the top, though separated by a valve. Apart from the lubrication function, mucus also protects the oesophagus tissue from the very strong acid in the stomach some of which washes upwards every time the stomach valve opens to let in food into the stomach.

When there is a problem with this area, we get symptoms such as heartburn or worse an ulcer forming where the oesophagus no longer has the protective coating to prevent acid attacking. If that happens for a while, the body reacts by forming a scar, which leads to difficulty in swallowing and weight loss without trying. In the long term it is a precursor to oesophageal cancer, which is more common in Africa and Asia compared to the west.

So what is not enough? In some areas mucus is most critical, but in general the total area covered by mucus in the intestinal tract is very large, about 200-300 sq metres, equivalent to a large 3-4 bedroomed apartment in Nairobi. All this is covered by just one litre of mucus over a 24-hour period, an adult human produces everyday. Consider that when you next re-paint your house.

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