Bladder: Facts, Function & Diseases

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Bladder: Facts, Function & Diseases

Bladder: Facts, Function & Diseases

Two long tubes called ureters connect the bladder, which stores urine, to the kidneys, which produce urine.

Credit: Nerthuz | Shutterstock

The bladder is a round, bag-like organ that stores urine. It is located in the pelvic area, just below the kidneys and right behind the pelvic bone. While it is basically a fleshy storage tank, it is very complex in its design.

The bladder is typically the size of a large grapefruit, according to the Weill Cornell Medical College. It can stretch much larger when needed, though, and shrinks back when it is empty. In fact, it can hold around 16 ounces (almost half a liter) of urine at one time for two to five hours comfortably, according to the U.S. National Library of Medicine (NLM).

It is normal to urinate around six to eight times in a 24-hour period, according to the Cleveland Clinic. More frequent trips to the bathroom may indicate a problem with the bladder, though it is common to urinate more as one ages.

The bladder is connected to the kidneys by two long tubes called ureters. When urine is produced by the kidneys, it travels down the ureters to the bladder, where it is stored. The bladder has four layers.

From the inside out, the epithelium is the first layer on the inside of the bladder. It acts as a lining for the bladder. The lamina propria is the next layer. It consists of connective tissue, muscle and blood vessels. Wrapped around the lamina propria is the layer called the muscularis propria or detrusor muscle. According to John Hopkins Pathology, this layer consists of thick, smooth muscle bundles. The final, outer layer is the perivesical soft tissue, which is made up of fat, fibrous tissue and blood vessels.

The other parts of the bladder are located at the bottom of the sack. An opening at the bottom of the bladder is connected to the urethra. A circular, muscular sphincter pinches tight to keep the opening and the urethra from leaking urine.

When a person urinates, the detrusor muscles contract to squeeze the urine out of the bladder while the sphincter relaxes to open the opening of the bladder and urethra. The opening at the bottom of the bladder empties urine into the urethra, where it then empties from the body.

Many diseases and conditions can originate in the bladder. “The most common bladder problems I see in my practice in women are frequent urges to urinate and leakage of urine,” said S. Adam Ramin, urologic surgeon and founder of Urology Cancer Specialists in Los Angeles, California. Leakage and frequent urges often are caused by the decreased capacity of the bladder and overactivity of the bladder. An overactive bladder can be caused by a wide range of conditions, including constipation and excess caffeine in the system, according to the Mayo Clinic. Leakage of urine, or incontinence,can also be caused by bladder spasms or stress. A bladder sling is sometimes used to treat stress urinary incontinence.

“The most common bladder problems in men are frequent urination at nights and incomplete bladder emptying. This is usually due to an enlarged prostate causing obstruction of bladder emptying,” Ramin told Live Science.

Bladder infections may be another cause of frequent urination. Bladder infections, also called cystitis, are among the most common bacterial infections, according to Harvard Health. Around one-third of all females get a bladder infection at least once. Some of the symptoms include burning or pain during urination, needing to urinate a lot though only a small amount of urine is passed each time, sudden needs to urinate, lower abdomen pain and cloudy or bloody urine.

Another problem that can originate in the bladder is bladder cancer. About 577,400 people in the United States live with bladder cancer, according to the National Cancer Institute. It typically affects older people, though younger people have been known to develop bladder cancer, according to the Mayo Clinic. Some symptoms of bladder cancer include blood in the urine, frequent or painful urination and back or pelvic pain.

An anterior prolapse, also called a prolapsed bladder or cystocele, is a bladder problem specific to females. It happens when the tissue between a woman’s bladder and vaginal wall weakens due to a strain. The weakening allows the tissue to stretch and the bladder bulges into the vagina, according to the Mayo Clinic.

Bladder stones are caused by concentrated urine that crystalizes in the bladder. Typically, people who have problems emptying their bladder have problems with bladder stones, according to the Mayo Clinic. Though many bladder stones are so small they can barely be seen with the human eye, one man was found to have an egg-shaped bladder stone that weighed 1.7 lbs. (770 grams) and measured 4.7 inches by 3.7 inches by 3 inches (12 by 9.5 by 7.5 centimeters). This isn’t the largest bladder stone on record, though. The largest bladder stone was 7 inches long, 5 inches thick and 3.7 inches tall (17.9 by 12.7 by 9.5 cm), and weighed 4.2 lbs. (1.9 kg), according to Guinness World Records. [Related: This Man’s Bladder Stone Was Almost as Big as an Ostrich Egg]

Sometimes, there is no choice but to hold urine, but it may not be good for the bladder. “Holding your urine for a short period of time, usually up to one hour, is typically okay,” Ramin said. “However, protracted and repeated holding of urine may cause over-expansion of bladder capacity, transmission of excess pressure into the kidneys, and the inability to completely empty the bladder. These problems in turn may lead to UTI [urinary tract infection], cystitis and deterioration of kidney function.”

Drinking plenty of water throughout the day can also help prevent bladder stones by preventing the concentration of minerals that cause the stones. The Mayo Clinic suggests asking a medical profession about how much water the body needs according to age, size and activity level.

Editor’s Note: If you’d like more information on this topic, we recommend the following book:


Circulatory System: Facts, Function & Diseases

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Circulatory System: Facts, Function & Diseases

Colon (Large Intestine): Facts, Function & Diseases

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Colon (Large Intestine): Facts, Function & Diseases

The body has two types of intestines. The small intestine is connected to the stomach and handles the middle part of the digestion process. The large intestine, also called the colon, is part of the final stages of digestion. It is a large tube that escorts waste from the body.


The colon is much wider than the small intestine, but is also much shorter. According to theCleveland Clinic, the small intestine is 22 feet (6.7 meters) long. The colon is only 6 feet (1.8 m) long.

This 6 feet of dense muscle is divided into four parts: the ascending colon, the transverse colon, the descending colon and the sigmoid colon. Each part represents a location in the broken rectangle shape that the colon makes in the body. The ascending colon is the right arm of the broken rectangle. The beginning of the ascending colon is called the cecum. The cecum is connected to the small intestine and the appendix.

The transverse colon is the top arm that spans from the left side to the right side like a bridge. The left arm is called the descending colon. The sigmoid is the “broken” part of the rectangle that creates an S-shape that hangs off of the descending colon. It empties into the rectum.


The function of the large intestine is to get rid of food left over after the nutrients are removed from it, bacteria and other waste. This process is called peristalsis and can take around 36 hours, according to the Cleveland Clinic.

First, liquid and salt is removed from the waste as it passes through the colon. Then, the waste makes its way to the sigmoid, where it is stored. Once or twice per day, when the body is ready for a bowel movement, the waste is dumped into the rectum.

Diseases & conditions

There are many diseases and conditions that are associated with the colon. Colorectal cancer is cancer that occurs in the colon or in the lower colon near the rectum.  It is one of the most common causes of cancer-associated death. The American Cancer Society estimates there will be 93,090 new cases of colon cancer in the United States in 2015 and one in 20 will get colorectal cancer in their lifetime.

Polyps are an abnormal growth of tissue on the inner lining of the colon or rectum that are benign, non-cancerous tumors, according to the American Cancer Society. These polyps can sometimes turn into cancer, but many times do not. There are several types of polyps. Adenomatous polyps can change into cancer and are considered pre-cancerous. Hyperplastic polyps and inflammatory polyps are not typically pre-cancerous, though some in the medical community think they may be signs of future colon cancer, according to the American Cancer Society. Doctors usually remove all polyps, just in case.

Colon dysplasia is when a spot of cells on the lining of the colon look abnormal under a microscope. These cells are not cancerous, but can change into cancer over time. People who have had diseases such as ulcerative colitis or Crohn’s disease for many years can develop colon dysplasia.

Spastic colon, also called irritable bowel syndrome, is more than just a colon problem. It is the spontaneous contractions or loss of movement of the muscles in the small and large intestines, according to the Mayo Clinic.

Promoting good colon health

There are many ways to improve large intestine health. Eat a healthy, balanced diet that is full of fruits and vegetables, consume fiber-rich diet, drink adequate amounts of water, exercise regularly and follow recommended guidelines for colon cancer screening and colonoscopies, Dr. Ajay Goel, director of epigenetics, cancer prevention and genomics at Baylor University Medical Center in Dallas, Texas, told Live Science.

Supplements, such as curcumin and omega-3, can help reduce chronic inflammation, said Goel. Other vitamins can be helpful, as well. “Low vitamin B6 levels have been associated with increased risk of certain cancers, such as colon and cognitive decline,” Dr. Sherry Ross, women’s health expert at Providence Saint John’s Health Center in Santa Monica, California, told Live Science.

study shows that taking both curcumin and boswellic acids may help prevent colon cancer. “We have known for a while that curcumin and boswellia both have potent anti-cancer properties,” said Goel, one of the study’s authors. “In this study, we investigated how they work in conjunction to reduce proliferation and increase cell cycle arrest and apoptosis (various mechanisms by which cancer cells are killed). We found that the two together activate a broader array of gene regulators called microRNAs, with a wider spectrum of impact compared to either compound individually.”

Colon cleanses

Many people use colon cleanses as a means to keep the colon healthy. This process includes taking laxatives, teas, powders or supplements, using enemas, or getting colonic irrigation (colon hydrotherapy) to flush out the colon. There can be side effects to cleansing, and some practices can even be dangerous. Doctors have varied opinions on cleansing. The colon’s very function is to remove toxins, so many doctors and medical groups, like the Mayo Clinic, believe that cleansing is unneeded and advise against it or to use caution. Others, like Goel, believe they can be helpful.

“Yes, colon cleanses can be very helpful in eliminating/washing away toxins from the body, but one must keep in mind that these cleanses (should be) as natural as possible and do not use strong/harsh chemicals, as these may provide temporary relief, but in the long run can negatively impact your colon health,” said Goel.

Nervous System: Facts, Function & Diseases

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Nervous System: Facts, Function & Diseases

The nervous system is a complex collection of nerves and specialized cells known as neurons that transmit signals between different parts of the body. It is essentially the body’s electrical wiring.

Structurally, the nervous system has two components: the central nervous system and the peripheral nervous system. According to the National Institutes of Health, the central nervous system is made up of the brain, spinal cord and nerves. The peripheral nervous system consists of sensory neurons, ganglia (clusters of neurons) and nerves that connect to one another and to the central nervous system.

Functionally, the nervous system has two main subdivisions: the somatic, or voluntary, component; and the autonomic, or involuntary, component. The autonomic nervous system regulates certain body processes, such as blood pressure and the rate of breathing, that work without conscious effort, according to Merck Manuals. The somatic system consists of nerves that connect the brain and spinal cord with muscles and sensory receptors in the skin.

Description of the nervous system

Nerves are cylindrical bundles of fibers that start at the brain and central cord and branch out to every other part of the body, according to the University of Michigan Medical School.

Neurons send signals to other cells through thin fibers called axons, which cause chemicals known as neurotransmitters to be released at junctions called synapses, the NIH noted. A synapse gives a command to the cell and the entire communication process typically takes only a fraction of a millisecond.

Sensory neurons react to physical stimuli such as light, sound and touch and send feedback to the central nervous system about the body’s surrounding environment, according to the American Psychological Association. Motor neurons, located in the central nervous system or in peripheral ganglia, transmit signals to activate the muscles or glands.

Glial cells, derived from the Greek word for “glue,” are specialized cells that support, protect or nourish nerve cells, according to the National Institute on Aging[Related: 10 Things You Didn’t Know About the Brain]

Infographic: Drawing shows the parts of the human nervous system.

Find out about the workings of the brain and nerves.
Credit: Ross Toro, contributor

Diagnosing nervous system conditions

There are a number of tests and procedures to diagnose conditions involving the nervous system. In addition to the traditional X-ray, a specialized X-ray called a fluoroscopy examines the body in motion, such as blood flowing through arteries, according to the NIH.

Other standard neurological exams include an MRI (magnetic resonance imaging), CT scan, and an electroencephalogram (EEG), which records the brain’s continuous electrical activity. Positron emission tomography (PET) is a procedure that measures cell or tissue metabolism and brain activity to detect tumors or diseased tissue or tumors, the NIH noted.

A spinal tap places a needle into the spinal canal to drain a small amount of cerebral spinal fluid that is tested for infection or other abnormalities, according to the NIH.

Diseases of the nervous system

“Of all the diseases of the nervous system, the most common difficulty that people have is pain, and much of that is nerve-related,” according to Dr. Shai Gozani, founder and CEO of NeuroMetrix, a medical device company. “There are 100 million people who live with chronic pain.”

According to the Mayo Clinic, patients with nerve disorders experience functional difficulties, which result in conditions such as:

  • Epilepsy, in which abnormal electrical discharges from brain cells cause seizures
  • Parkinson’s disease, which is a progressive nerve disease that affects movement
  • Multiple sclerosis (MS), in which the protective lining of the nerves is attacked by the body’s immune system
  • Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, is a motor neuron disease which weakens the muscles and progressively hampers physical function
  • Huntington’s disease, which is an inherited condition that cause the nerve cells in the brain to degenerate
  • Alzheimer’s disease, which covers a wide range of disorders that impacts mental functions, particularly memory.

Mayo Clinic also noted that the nervous system can also be affected by vascular disorders such as:

  • Stroke, which occurs when there is bleeding on the brain or the blow flow to the brain is obstructed;
  • Transient ischemic attack (TIA), which are mini-type strokes that last a shorter period of time but mimic stroke symptoms; and
  • Subarachnoid hemorrhage,  which is specifically bleeding in the space between your brain and the surrounding membrane that can be the result of a trauma or rupturing of a weak blood vessel;

Infections such as meningitis, encephalitis, polio, and epidural abscess can also affect the nervous system, the NIH noted.

Treatments vary from anti inflammatory medications and pain medications such as opiates , to implanted nerve stimulators and wearable devices, Gozani said. “Many people also turn to herbal and holistic methods to reduce pain, such as acupuncture.”

Study of the nervous system

The branch of medicine that studies and treats the nervous system is called neurology, and doctors who practice in this field of medicine are called neurologists. Once they have completed medical training, neurologists complete additional training for their specialty and are certified by the American Board of Psychiatry and Neurology (ABPN).

There are also physiatrists, who are physicians who work to rehabilitate patients who have experienced disease or injury to their nervous systems that impact their ability to function, according to the ABPN.

Neurosurgeons perform surgeries involving the nervous system and are certified by the American Association of Neurological Surgeons.

Editor’s Note: If you’d like more information on this topic, we recommend the following book:

Nose: Facts, Function & Diseases

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Nose: Facts, Function & Diseases

The human nose is more than just a flap of flesh and cartilage on the front of the face. Besides being part of the respiratory system that inhales oxygen and exhales carbon dioxide, the nose also contributes to other important functions, such as hearing and tasting.

Size and shape

Human noses can have a wide array of shapes and sizes due to genetics and injuries. Men generally have larger noses than women, researchers say. According to the Guinness Book of World Records, the largest human nose on a living person belongs to Mehmet Ozyurek of Turkey. His nose is 3.46 inches (8.8 centimeters) long from the bridge to the tip.


The two openings in the nose care called nostrils, or napes. They lead to two nasal cavities that are separated by the septum, a wall of cartilage. Inside the face is an intricate system of canals and pockets of air called sinus cavities. Sinus cavities span all the way to the back of the skull, right above the oral cavity, within the cheekbones and between the eyes and brows. All of these areas are responsible, at least in part, for breathing, smelling, tasting and immune system defense.


 The human nose can smell over 1 trillion scents, according to researchers. The nose smells with the olfactory cleft, which is the roof of the nasal cavity. It is right next to the “smelling” part of the brain, which consists of the olfactory bulb and fossa. This part of the nose has many nerve endings that carry smell sensations to the brain, according to the American Rhinologic Society.The nasal passageways on either side of the nose open into the choana and then into a chamber called the nasopharynx, which is the upper part of the throat. This chamber opens into the oropharynx, the throat area behind the mouth. When air is inhaled through the nostrils, it travels through the nasal passages, the choana, the nasopharynx, the oropharynx and the voice box and ends up in the lungs. Basically, in therespiratory system, the nose is a passageway for air.

Sinuses, nose
Sinus cavities span all the way to the back of the skull, right above the oral cavity, within the cheekbones and between the eyes and brows.
Credit: Sebastian Kaulitzki | Shutterstock

Snot and boogers

The nose is also the first line of defense against sickness. The nose is lined with fine, hair-like projections known as cilia. The sinuses are lined with mucus-making cells. The mucus (or “snot”) keeps the nose from drying out. Together, cilia and snot collect dust, bacteria and other debris before they can enter the rest of the body, according toEncyclopedia Britannica. [Infographic: What Your Snot Says About You]

Typically, nasal mucus — made of water, proteins, antibodies and salts — is clear. But during an infection, snot can change to yellow or green, indicating the body is fighting off a bacterial or viral infection. The green color comes from a chemical secreted by white blood cells — specifically, the heme group in the iron-containing enzyme myeloperoxidase — to kill pathogens.

Clumps of dried mucus, dirt and debris are called “boogers,” and despite the taboo, one Canadian scientist thinks “picking your nose” — and eating your boogers — may be good for you.

Scott Napper, a biochemistry professor at the University of Saskatchewan, hypothesizes that snot tastes sweet for good reason (take his word for it or try it yourself). That may be a signal to the body to eat it and get immune-boosting benefits.

“By consuming those pathogens caught within the mucus, could that be a way to teach your immune system about what it’s surrounded with?” Napper told the Canadian Broadcasting Corporation.

His hypothesis fits on with other theories about the link between improved hygiene and an increase in allergies and autoimmune disorders, he said. “From an evolutionary perspective, we evolved under very dirty conditions and maybe this desire to keep our environment and our behaviors sterile isn’t actually working to our advantage.”

Other senses

Without the nose, the body wouldn’t be able to taste food nearly as well. What humans call “taste” is actually a mixture of different sensations. One of the sensations is smell. When food is eaten, the nose smells the food and sends information to the mouth in a process called olfactory referral. This is why those with a cold or other nose condition finds that food lacks flavor.

The nose also plays a role in hearing. The nasopharynx is flanked on either side by eustachian tubes. These tubes connect the nasopharynx to the middle ear. The nasopharynx fills the middle ear with air, equalizing air pressure in the ear with the atmosphere around it, which is an important part of hearing properly, according to the American Rhinologic Society.

Diseases & conditions

Since the nose is complex, there are many things that can go wrong. “The most common ailments people come to our office with are difficulty breathing through the nose, nasal obstruction, nasal allergies, chronic sinus infections, and nasal polyps. Another thing we’re seeing more of is people coming in for a poor sense of smell,” said Dr. Seth J. Kanowitz, attending physician at the Department of Otolaryngology at the Morristown Medical Center in Morristown, New Jersey, and co-director of the hospital’s skull-based surgery program.

The most common cause for the loss of the sense of smell is a viral infection, like a cold, Kanowitz told Live Science. Sinus infections, nasal polyps, tobacco use, head trauma and, in exceedingly rare instances, tumors, may also cause smell loss. Some loss of smell also occurs during the natural aging process, much akin to visual and hearing loss.

Sinusitis is another common nose condition. “Sinusitis is a condition meaning inflammation of the sinuses,” Dr. Rob Straisfield, medical contributor for MJ Wellness, told Live Science. The inflammation can come from allergies, viruses and certain diseases. Some symptoms are weakness, fever, fatigue, cough and congestion, according to the U.S. National Library of Medicine (NLM).

The nasal septum, the flat plate of cartilage in the center nose, can be damaged and pushed to the left or right, or the nose can grow crookedly. This condition is called a deviated nasal septum. A deviated septum can cause breathing problems and discomfort because one or both of the nasal chambers are smaller than they are supposed to be. Sometimes a deviated septum is corrected with surgery.

Many people have problems with clogged sinuses or a stuffy nose. This can be caused by swollen tissue or the blockage of mucus. Often, these problems can be dealt with at home. “Nasal saline irrigations with high volume, low pressure bottles have been shown to be very effective to keep the nasal passageways clear, remove allergens and thick mucus, and alleviate sinus infections — potentially removing the need for antibiotics,” Kanowitz said.

Things coming out of the nose can be a problem. A runny nose is caused by the production of mucus in the nose. The production of mucus can be triggered by anything that irritates or inflames the nose, such as allergies, a cold, the flu or dust, according to the Mayo Clinic. Bloody noses are caused when the tiny blood vessels in the nose break due to dry air, irritants, chemicals, impacts to the nose and various other factors.

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