Having a bowel movement is something we do regularly, either every day or every two or three days. In this case each master has his booklet. Now, eating has a voluntary component that prevents us from going down the drain at the most inopportune moments. What’s more, if we repress it, we don’t feel like it again until there are mass movements of the intestine, usually after meals.
Inside the body, everything begins in the rectal ampulla, which serves as a temporary store for material that has become expendable. When the amount of accumulated material increases, stretch receptors in the walls of the rectum send a signal that causes the rectal muscles to contract and the internal anal sphincter to relax. These events send the signal to the brain that “it’s time to exonerate the belly.” If we find ourselves in an unfavorable situation and we hold on, sometimes the material returns to the colon through reverse peristalsis – the same mechanism that allows us to vomit. By keeping the feces inside the body, the water they contain is absorbed and they harden until, if we do not comply with our physiological tasks, it leads to constipation.
But if we have managed to find a bathroom, the rectum shortens and peristaltic waves are produced that push the fecal matter to the anus. Meanwhile, the internal sphincter opens thanks to the intervention of the sacral nerve , whose function is to control urination, defecation and erection, and it is the one that tells us that both the bladder and the rectum are overflowing. The show is about to end, and that’s where we come in: the relaxation of the external sphincter is a voluntary act that is carried out by the so-called pudendal nerves.
To be able to have a bowel movement we must take a breath and perform what is known as the Valsalva maneuver , in honor of the 17th century Italian doctor Antonio Maria Valsalva. It consists of expelling the air with the glottis closed (the narrowest part of the larynx); just what we do when our ears get clogged up. This movement exerts effective pressure on the digestive tract: we are “pulling”. During defecation, blood pressure increases and, as a reflex response, the amount of blood pumped by the heart decreases. On rare occasions, this increase in pressure has caused the death from a ruptured aneurysm, an inelegant way to leave this world.
Looking at physiology it is clear that, although the position we use to defecate depends on our culture, there is one that is natural and we observe it in all primates: squatting. We will use this posture if we find ourselves before a Turkish plate, a piece of metal or earthenware with a hole in the middle, very common in Asia. In the West we are more into sitting, although our traditional toilet is not as old as we think. It was invented by Joseph Bramah in 1778, when his patent improved on earlier designs. In fact, his original designs can still be seen at Osbourne House, Queen Victoria’s home on the Isle of Wight in England. But let’s not forget that, as the classic textbook Bockus Gastroenterology says , ” the ideal position for defecation is squatting, with the thighs on the abdomen . In this way the capacity of the abdominal cavity decreases while the intra-abminal pressure increases , stimulating the expulsion”.
Except for gastrointestinal problems, the frequency of visits to the WC varies from once every two or three days to different times a day, depending on the idiosyncrasy of each one. If you look closely, our stools have a brownish color, a combination of bile and bilirubin , a yellow-orange substance that comes from the breakdown of hemoglobin. In newborns, fecal matter is yellowish green after meconium (this is what a baby’s first stool is called), due to the presence of bile. Over time, as the body begins to excrete bilirubin, it acquires its characteristic brown colour, unless the child is breastfed: then his stools will be pale yellow and will not have its peculiar bad smell.
Throughout life we can experience many types of feces. A green stool comes from a very rapid intestinal transit and the slate-colored appearance is the result of the absence of bilirubin. Food also contributes its bit to the appearance of the stool. The undigested food found in them is usually seeds, nuts or corn, mainly because of its high fiber content. Beetroot can turn our stools into different shades of red, and the artificial colors often used in certain breakfast cereals can give them a kaleidoscopic appearance if eaten in sufficient quantity.
Its distinctive odor is due to the intestinal flora, which produces sulfur compounds such as indole, skatole and thiols or mercaptans (present in mouth odor and skunks), as well as hydrogen sulfide and its characteristic odor to rotten eggs: these same molecules are part of flatulence.
But what is really striking is that until 1992 the shape and type of feces have not been scientifically studied. This luminous work was carried out by the doctor KW Heaton in the city of Bristol. To do this, he asked 838 men and 1,059 women to describe the shape of their stools during three consecutive bowel movements. This allowed him to create a scale of 7 types where both its appearance and its consistency are described. In this study, it is observed that “sausage-shaped, smooth and soft” stools are the most frequent in both sexes , while hard stools are more frequent in women than in men and soft stools are more frequent among men. But the important thing came in 1997, when Heaton and his collaborator Lewis showed that there was a correlation between the shape of the stool and the total intestinal transit time. Assuming the validity of this idea, in 2007 RS Choung and his colleagues at the Mayo Clinic in Rochester (USA) conducted a postal survey in Minnesota. Referred to 4,196 people (of whom just over half responded) they also found a correlation between the type of stool and transit time . The same has been discovered in our country, as reported by D. Parés and his collaborators at the Hospital Universitario del Mar in Barcelona in the May 2009 issue of the Spanish Journal of Digestive Diseases . Tell me how you shit…
