What Does the Bladder Do?

by Katrina Cain on January 14, 2010

Major elements of the urinary system

The urinary bladder, as it is referred to anatomically to distinguish it from meaning “pouch or flexible enclosure”, sits atop your pelvic floor: protective layers of muscles and connective tissues designed to hold you internal organs in place. The bladder is the final internal destination for urine that has been collected and concentrated by the kidney and transported via the ureters – one for each kidney.

The urinary bladder; like the design of many other internal surfaces of your body, like the small intestine and the stomach is lined with folds of tissue. In the stomach and bladder, these folds are called rugae and they stretch and flatten in response to increased pressure – if you have just eaten a big meal or haven’t urinated in a long time. Our wonderful bodies follow this design because internal bladder expansion takes the pressure off the surrounding pelvic and abdominal organs. In contrast, if the bladder filled outwards like a balloon, our pelvic and abdominal muscles would be continually squashed.

We start feeling the urge to pee when our bladder is about 25% full. For most people; this pretty easy to ignore. Nerves on and near our bladder, when stretched, trigger the parasympathetic nervous system (the rest and digest part of our nervous system as opposed to the sympathetic fight or flight part of our nervous system) to signal us to go pee. As the bladder stretches, the PNS becomes more insistent that we go pee. If the bladder reaches 100% capacity you will expel urine involuntarily. The flow of urine is controlled by two muscles; an internal involuntary muscle called the detrusor muscle and an external voluntary Kegel muscle.

OK, a brief aside to explain involuntary and voluntary muscle: involuntary muscles are controlled directly by our nervous system without conscious input from us. They are made up of smooth muscle fibres. Skeletal muscle, under our voluntary control is also regulated by our nervous system, but we are the ones sending the signals to the brain to move or not move. Skeletal muscle is striated. Microscopically, they look very different from each other. Smooth muscles are working away in your body all the time; like for example, in your small intestine as the smooth muscles push food along the digestive tract towards the large intestine (or colon) and out the anus.

Kegel muscle a.k.a. the Pubococcygeus muscle

It is our voluntary muscle we contract to “hold pee in” You can strengthen this muscle by doing Kegel exercises – for women, flexing the little ring of muscles, inside your vaginal opening. Doing about 25 flexes of this muscle every day well help to prevent urinary incontinence problems when you are older. Men also have a Kegel muscle that allows their penis to stay erect, and controls their ejaculation and of course, help with incontinence. Men can isolate and strengthen this muscle by stopping and starting the flow when urinating. This is the same for women.

What can go wrong? Well it all boils down to incontinence, but for many different reasons. If you have damaged nerves, you may not be able to receive the PNS’s signals urging you to urinate as is the case with some Parkinson’s and Multiple Sclerosis patients. Your detrusor muscle (involuntary) is controlled by the PNS. If your PNS is damaged, this muscle may not function properly, and the only protection you have is your external muscle; which is likely not strong enough to hold back small outputs of urine. Prostate cancer can damage pelvic nerves resulting in incontinence.

Sometimes (mostly in women), if you laugh, sneeze or cough, the pressure it creates overcomes both sets of muscles resulting in little spurts of urine coming out. This is called Stress Incontinence and happens mostly in older women – over the age of 60, but can happen younger; say if you have a genetic predisposition to urinary incontinence.

Overactive bladder is diagnosed when you have to pee 8 or more times a day, and are up 1 or 2 times a night. Based on this definition approximately 1 in 6 people in the U.S. have this problem. OAB can be treated with antimuscarinic drugs or through a really cool sounding procedure whereby physicians insert an electrode near the tibial nerve in your leg. An electrical impulse travels to your sacral plexus via your tibial nerve. Recall, that your tibia is a bone in your lower leg. Your sacral plexus is a bundle of nerve fibers responsible for controlling parts of your pelvis and lower extremities. The treatment takes place once a week for 12 weeks. Some patients need more or ongoing treatment. I myself have an overactive bladder, but it doesn’t badly interfere with my life – excepting 11 hour long bus rides in Central Turkey with only one bathroom stop; I have just lived with it without treatment. Please understand, I am not a medical professional and I am not advocating any procedure or treatment, but just seek to educate people about our bodies and how they work. Peace out.

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