During a bowel movement, the indigestible parts of our food (called "stool" or "poo") leave our body. It is usually possible to control bowel movements with the help of several parts of the end of the digestive tract: the rectum and anal canal, the sphincters (circular muscles), and hemorrhoids. These parts are embedded in the pelvic floor muscles.
The lower end of the gastrointestinal tract
Rectum and anal canal
The rectum, which is about 20 centimeters long, is the final section of the large intestine (colon). This is where the indigestible parts of our food collect until the bowel is emptied. The anal canal, situated between the rectum and anus, is closed off by sphincter muscles and hemorrhoids. It is between three and six centimeters long, and has a mucous membrane lining (anoderm). This lining contains a lot of nerves that send signals to help the brain do things like recognize the consistency of stool and how full the bowel is. These nerves also help you know when your bowel needs to be emptied.
Anal sphincters
There is an inner (internal) and outer (external) sphincter at the end of the anal canal. These muscles close off the opening of the bowel (anus). The inner sphincter makes sure that the rectum doesn't open when you're sleeping, for example. It is ring-like in shape and made up of smooth muscle.
The outer sphincter supports the inner sphincter, helping it to perform its function. Unlike the inner sphincter, the outer sphincter can be controlled voluntarily. This makes it possible to empty your bowels or hold back your stool when you want to. But the outer sphincter can also act involuntarily, for instance to help or prevent the passage of stool.
Hemorrhoids
Hemorrhoids are “cushions” of blood vessels and supporting tissue, found at the end of the rectum, just before the anus. Together with the anal sphincters, they close off the bowel, preventing stool from leaving the body. Enlarged hemorrhoids can cause unpleasant symptoms. This is what most people mean when they talk about having hemorrhoids, also known as “piles.”
Pelvic floor
The pelvic floor is made up of muscles, ligaments and connective tissue. It physically supports the pelvic organs, and closes off the lower part of the pelvic cavity. Openings in this strong sheet of muscular tissue allow the vagin*, the last part of the bowel (rectum), and the tube that you pee out of (urethra) to pass through it. The pelvic floor relaxes when you go to the toilet and have a bowel movement, and it contracts (squeezes) when you hold stool back.
What makes you feel the urge to “go”?
When the rectum fills up, stretch receptors in the wall of the anus are alerted. Signals are sent along nerve pathways to the part of the brain known as the cerebrum. There they are processed, and signals are sent back to the lining of the anus. The nerve impulse causes the inner sphincter to open, making you feel like you need to empty your bowels. The pelvic floor relaxes and drops down a little, allowing the muscle in the rectum to push the stool out.
If you follow the urge to empty your bowels, and go to the toilet, you voluntarily relax your outer sphincter muscle as well. But you can hold back stool for some time by tensing the muscles in your pelvic floor and abdomen, as well as your outer anal sphincter. After a bowel movement, the inner sphincter closes again too and you no longer feel the urge to go to the toilet for a while.
Sources
Brandes R, Lang F, Schmidt R. Physiologie des Menschen: mit Pathophysiologie. Berlin: Springer; 2019.
Butt S, Eberhard-Metzger C, Federspiel K et al. Der Gesundheitsbrockhaus. Kursbuch Mensch: Aufbau, Funktion, Entwicklung, Krankheit und Heilung. Mannheim: F.A. Brockhaus; 2001.
Menche N. Biologie Anatomie Physiologie. München: Urban und Fischer; 2016.
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FAQs
The pelvic floor relaxes and drops down a little, allowing the muscle in the rectum to push the stool out. If you follow the urge to empty your bowels, and go to the toilet, you voluntarily relax your outer sphincter muscle as well.
How do you work out your bowel movements? ›
Whether it's running, swimming, cycling, or dancing, a cardio workout will increase your breathing, boost your heart rate, and stimulate your bowels. Even if you don't feel up to a full-on workout, just going for a brisk 30-minute walk can do wonders for your digestive system.
What is the explanation of bowel movements? ›
Movement of feces (undigested food, bacteria, mucus, and cells from the lining of the intestines) through the bowel and out the anus. Also called defecation.
How do you describe a bowel movement? ›
A bowel movement is the last stop in the movement of food through your digestive tract. Your stool passes out of your body through the rectum and anus. Another name for stool is feces.
How does the bowel system work? ›
Once all the nutrients have been absorbed, the waste is moved into the large intestine, or bowel. Water is removed and the waste (faeces) is stored in the rectum. It can then be passed out of the body through the anus.
How is a normal bowel movement? ›
A person's poop tends to be brown, soft to firm in texture, and easy to pass. If someone experiences changes in poop, they should monitor them and consult a doctor if the issue does not resolve within 2 weeks.
What simple trick empties your bowels immediately? ›
Try These Tricks for Quick Bowel Movement Stimulation
- Drink coffee. Regarding drinks that make you poop, coffee is probably the first that comes to mind. ...
- Squat when you poop. ...
- Use a fiber supplement. ...
- Take a stimulant laxative. ...
- Take an osmotic laxative. ...
- Take a lubricant laxative. ...
- Try a stool softener. ...
- Use a suppository.
It won't go away on its own, and it can lead to death if it's allowed to worsen. The most common treatment for a fecal impaction is an enema, which is a special fluid that your doctor inserts into your rectum to soften your stool.
What exercises open your bowels? ›
If you are already fit, you might choose aerobic exercise: running, jogging, swimming, or swing dancing, for example. All of these exercises can help keep the digestive tract healthy. Stretching may also help ease constipation, and yoga may, too.
Where is poop stored when constipated? ›
What is fecal impaction? Fecal impaction is the result of severe constipation, when you're unable to regularly pass poop (stool or feces) and it backs up inside your large intestine (colon). Fecal impaction can also be defined by your inability to sense and respond to the presence of stool in your rectum.
How long it takes you to poop. It should take just a couple minutes for you to have a bowel movement – certainly not more than 10-15 minutes. If there's pain or straining to get your poop out, you're probably constipated.
How to train your bowels to go in the morning? ›
Find a regular time each day where you would not be interrupted (doing this in the morning after breakfast is usually the best time). Sit on the toilet for a fixed amount of time usually about 15 minutes. It's preferable to do this 10 to 20 minutes after a meal with coffee.
What triggers a bowel movement? ›
When enough stool moves to the rectum, the amount of stool causes the tissues in the rectum to stretch or distend. Inside these tissues are special “stretch” receptors designed to signal the brain when they are stretched. The defecation reflex triggers the two main sphincters around the anal canal.
Can only pass small amounts of stool? ›
An incomplete bowel movement—the feeling that you still have to poop, even when you don't—can be uncomfortable and frustrating. Also known as incomplete evacuation, it is a hallmark of irritable bowel syndrome (IBS). It can also be caused by chronic constipation, pelvic floor disorders, and infections.
Why does my poop come out in small pieces? ›
When an individual is constipated, stool remains in the large intestine too long, giving the intestine more time to absorb water. This dries out the stool and turns it into a large, hard mass that is more difficult to pass. In certain cases, this mass can break apart into smaller lumps of stool, causing pebble poop.
How to completely empty your bowels? ›
Lean forward on the toilet with your forearms resting on your thighs, your legs more than hip width apart and your feet raised up on a small foot stool. Repeat for up to 10 minutes only or until your bowel has emptied. If you don't pass anything try again when you have another urge to go or the following day.
Should I push when I poop? ›
Straining while pooping may happen from time to time, but regular straining may injure the rectum. Hemorrhoids, anal fissures, and other complications may result from excessive straining. To avoid straining, a person can try staying hydrated, eating a diet high in fiber, and staying active.
Why do I feel like I have to poop but only a little comes out? ›
Tenesmus is a feeling of being unable to empty the bowel or bladder. It usually refers to rectal tenesmus, which can occur with inflammatory bowel disease (IBD), rectal cancer, and other conditions. Vesical tenesmus is a separate condition that relates to the bladder.
