What causes constipation? - Heba Shaheed

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Visiting the bathroom is part of the daily human experience. But occasionally, constipation, a condition that causes a backup in your digestive system, strikes. In some especially uncomfortable cases, the food you eat can take several days to exit your body. What's behind this unsettling phenomenon? Heba Shaheed takes us into the digestive system to find out.

Lesson by Heba Shaheed, animation by Augenblick Studios.

Visiting the bathroom is part
of the daily human experience.

But occasionally, constipation strikes,

a condition that causes
a backup in your digestive system.

The food you eat can take several days
to exit your body.

And for many,
constipation can become chronic,

meaning regularly passing lumpy
hard stools accompanied by straining.

What's behind this
unsettling phenomenon?

Constipation arises in the colon,
also known as the large intestine.

This muscular organ is split
into four sections:

the ascending,

transverse,

descending,

and sigmoid colon,

which connects with the rectum and anus.

The small intestine delivers stool

consisting of ingested food,
bile, and digestive juices

to the large intestine.

As this stool moves through the colon,

the organ siphons off most
of the water it contains,

transforming it from liquid to solid.

The longer this transmission takes,

the more reabsorption occurs,
resulting in increasingly solid stool.

Once it reaches the sigmoid colon,

a final bout of reabsorption
occurs before it enters the rectum,

distending its walls and telling
the internal anal sphincter to relax.

This is the point where you can usually
decide whether to physically expel

or retain the stool.

That’s regulated by
the pelvic floor muscles,

particularly the puborectalis

and external anal sphincter.

The puborectalis forms
a sling-like formation around the rectum

called the anorectal angle.

And when you voluntarily relax
your external anal sphincter,

the stool is finally expelled.

When you’re constipated, however,

a desire to visit the bathroom isn't
enough to coax your body into action.

Usually there's two factors
behind this problem:

the stool’s slow movement
through the colon

and/or pelvic floor dysfunction.

In the first, stool moves excessively
slowly through the intestines,

causing over-absorption of liquid,
which makes the stool dry and hard.

With pelvic floor dysfunction,

stool becomes difficult
to eliminate from the rectum

because of tightened pelvic floor muscles,
or due to a pelvic organ prolapse,

usually through childbirth or aging.

Both of these problems
make the anorectal angle more acute

and it becomes difficult to expel waste.

To identify constipation precisely,

researchers have developed metrics,
such as the Bristol Stool Chart.

Most people who look at that chart

will be able to tell they’ve experienced
constipation before.

When you’re on the toilet, you should
ideally be in a squatting position.

With your buttocks firmly
on the toilet seat,

you can elevate your feet on a stool

and lean forwards with a straight back,

which straightens the anorectal angle
and eases the passage of waste.

Going a day without a bowel movement
isn’t necessarily cause for alarm.

But if you are experiencing
chronic constipation,

simple dietary and lifestyle changes,

like fibrous vegetables,

regular exercise,

abdominal massage,

and 6 to 8 cups of water per day

may help restore your daily
trip to the toilet.