The process of defecation, or passing stools, is the culmination of a long and complex process of digestion that is carried out in various parts of the digestive tract. Solid stools are formed in the large intestine (also known as the colon) after the absorption of water from the digested food material. The stools then pass from the lower part of the large intestine (the descending and sigmoid colon) into the rectum. The rectum is the last part of the digestive canal, and it holds the stools temporarily before they are excreted out of the body through the anal opening.
How does defecation start?
The process of defecation begins when the stool enters the rectum. The presence of stool in rectum stretches the walls of the rectum, which results in stimulation of stretch receptors present in these walls. Stimulation of stretch receptors initiates nerve signals to the central nervous system, resulting in an urge to pass stools. This urge continues to increase in intensity as the rectum keeps getting stretched by incoming stool from the colon.
The nerve signals caused by the stretching of the walls of the rectum also relax the internal anal sphincter. The internal anal sphincter is one of two anal sphincters that regulate the anal opening. Even after the involuntary relaxation of the internal anal sphincter, stool does not come out because the external anal sphincter remains closed. It requires a voluntary relaxation of the external anal sphincter to let the stool out.
In order to defecate, a person first finds an appropriate place (such as a toilet), and then adopts a sitting or squatting position. These positions help in the final act of passing the stool out of the anal opening.
Read more on bowel urging.
Sitting position for defecation
Modern toilets are raised platforms with seats on top. People sit on the toilet seats in order to complete the act of defecation. This sitting position is comfortable, and usually does not cause any problem for most people. However, in some cases (such as during constipation), the sitting position may require more straining or pushing in order to pass the stools. The reason for this extra strain can be understood by looking at the anatomical requirements of a smooth bowel movement.
For stools to pass out smoothly, both the rectum and the anal canal need to be aligned in a straight line. In the sitting position, the passage through the rectum and the anal canal is no longer straight. In this position, a bend or kink is introduced between the rectum and the anal canal. This bend or curvature is also called the anorectal angle.
During defecation, more straining (or push) is required to move the stools through the anorectal angle formed in the sitting position. Straining becomes more pronounced in conditions such as constipation, in which the stools are not as soft as those formed in normal conditions.
Read more on hard stool.
Squatting position for defecation
Toilets that support a sitting position for passing stools are considered the norm in Western countries. However, the predominant position adopted for passing stools in many other nations is a squatting position. The toilets in these countries are also built into the ground (rather than as a seat on a raised platform) to facilitate squatting for the act of defecation. In the squatting position, a person bends both knees fully in order to sit on the ground, with the buttocks left hanging in the air. The squatting position requires more physical dexterity than the sitting defecation position.
Which position is better for defecation?
It is still debatable as to which position is better suited for the act of defecation. The squatting position is considered a more natural position, which is adopted by people in many parts of the world. It is an instinctive position adopted by people while defecating in the open (in the absence of toilets).
The squatting position can also be considered an anatomically better position for defecation because the passage of stools between the rectum and the anal canal occurs in a straight path. Less effort (strain or push) is required to pass stools in this situation. This may be helpful in conditions such as constipation. A squatting toilet is also known as a natural position toilet.
Despite the advantages of the squatting position in passing stools, it is not suited for everybody or every condition. The squatting position requires more dexterity of the knee joints, which may not be possible for everybody (such as people with joint pains and the elderly). It also puts a lot of pressure on the abdomen, which is not convenient for obese people or pregnant women. Since the buttocks are left hanging in the air during a squat, this position requires strength and agility to balance oneself.
Considering these arguments, it becomes clear that the sitting position also has advantages over the squatting position in some situations and for some people.
Try To Squat If Possible
For most people in general, however, a squatting position is ideal. With the exception of those with certain physical constraints, people who normally use the sitting toilets can also adopt the squatting position as a natural way of defecation. It may be awkward at first, but with time this position will become a natural and comfortable way to pass stools.
In order to change from a sitting position to a squatting position, it is not necessary to rebuild Western style toilets as squatting toilets. It is possible to use the existing Western style toilets in a squatting position. Special squatting platforms are commercially available to enable a person to squat on top of a Western toilet. These squatting platforms enable squatting by raising the thighs of a person sitting on the toilet seat. This brings the thighs close to the abdomen, a posture that is similar to a squat.
Unlike in natural squatting, however, the buttocks are not suspended in the air while using the squatting platforms. This takes away a lot of stress from the knee and ankle joints, which are constant features of the natural squatting posture. It is also advisable to build hand rails near the toilet, so that one can grab on to them while squatting. This will make squatting easier for people who have difficulty balancing themselves (such as the elderly).