Excretory System Functions

  • What are over a dozen functions that the excretory system performs?
  • Does your excretory system play any role in detoxification and homeostasis?
  • How the skin, the liver and the lungs are the essential parts of the excretory system?
  • What are the therapies and preventive measures for the excretory system disorders?

Ralph W. Emerson once said, “As soon as there is life, there is risk.” So, a biologist might say, “As soon as there is life, there is waste”. All the living organisms produce waste products through different mechanisms and human beings are no exception to it. If accumulated in any part or organ of the body, the wastes will definitely cause harm. So, all living things face a common challenge regarding how to get rid of the internally produced wastes.[1]

In addition to the excretory system functions, here you’ll also learn about its parts, mechanics andcommon disorders along with therapies and effective preventive measures. In addition, over two dozen stunning facts about excretory system functions are also given.

What is Excretory System?

Your excretory system involves multiple organ systems which help the body for the removal of internally produced waste in the form of solid, semi-solid, liquid and gas. The urinary system is one of the sub-systems associated with excretory system.

The waste substances produced in the body include digestive waste, metabolic waste, gaseous waste, toxins and excess of anything. Your body needs to get rid of all these things and it is done with the help of the excretory system.

The digestive system waste consists of the indigestible food material which is collected in the large intestine for its removal out of the body through anus. Metabolic wastes are produced in every individual cell and need immediate disposal.

The metabolic wastes include ammonia, urea, uric acid, bile pigments, urochrome, carbon dioxide, water and inorganic ions.[2]

In addition to large intestine, rectum, anus, kidneys, ureters, urinary bladder and urethra, the excretory system also gets helpof several organs of other organ systems, including thelungs, the skin and the liver.[3]

Uremia, renal failure, kidney stones, nephritis, oedema, renal tabular acidosis and hypertension are some of the excretory system disorders.

Let’s learn about the excretory system functions, parts, working, diseases and facts in the following sections.

Excretion versus Elimination

According to Insel, P. et al (2015), the removal of digestive waste is called elimination while the process of excretion is particularly concerned with the removal of metabolic waste.[4]

The digestive waste consists of the unabsorbed leftover substances which pass along the gastrointestinal tract (like the esophagus, and the intestines, etc.) with the help of the peristaltic movements. Finally, they are emptied out of the body through the process of elimination.

On the other hand, the metabolic wastes are produced during various chemical reactions that take place in the cells across the body. These waste products are to be excreted with the help of the lungs and the kidneys which are the primary organs of excretion (Insel et all, 2015).[5]

However, there is no separate organ system as the elimination system. So, the process of elimination will be considered a part of the excretory system.

Excretory System Functions

There is a big misconception about the excretory system that it is concerned solely with the removal of indigestible organic and inorganic materials out of the body. In fact, it does a lot more. The second misconception is that it is a single organ system. Actually, for the execution of dozens of jobs assigned to it, the excretory system has to take help from many components of other organ systems, like respiratory system and integumentary system.

Along with being a passive biological system for the removal of excess and unnecessary materials, it also involves the detoxification of poisons and other harmful substances and assists in the maintenance of homeostasis within the body.

The large intestine and the rectum store the digestive waste and assist in its removal through the anus. The lungs, the liver, the skin and the urinary system are concerned with the removal of the waste produced during various metabolic activities.[6]

Some of the key excretory system functions are described in brief as under:

  • Elimination of Digestive Waste:

Everything you eat cannot be digested and utilized in the body. Working intelligently, your digestive system breaks down and takes only useful substances from the food. The digested matter is absorbed into the bloodstream across the wall of the small intestine. The remaining indigestible matter is to be excreted.

One of the major and most important duties assigned to this system is the removal of indigestible, semi-solid waste products. Moving along the alimentary canal, the digestive waste enters the large intestine for its temporary storage. However, in this organ of the excretory system, the leftover useful substances are reabsorbed, including salts, minerals, vitamins and water.

Finally, the waste and harmful substances are expelled out of the body in the form of semi-solid mass, called feces.

  • Ammonia Excretion:

    Ammonia, a waste product of metabolic activities in the body, is extremely soluble in water and it is also highly toxic to the tissues. Actually, the presence of ammonia causes an increase in pH of the body fluids and interferes with mechanisms for the transportation of ions. At the same time, the high concentration of ammonia may also affect synaptic transmission and the blood supply to the brain.[7]

Ammonia is produced in the process of deamination,or removal of amine group from amino acids,in the liver. On the other hand, kidneys are the organs responsible for the excretion of this highly toxic substance.[8]

  • Removal of Urea:

    Mammals, including humans, excrete urea as the principal form of nitrogenous waste. So, they are called the ureotelic animals. Urea is less toxic and less soluble in water than ammonia. Similarly, in the form of urea, more nitrogen is excreted with less water. The removal of 1 g of nitrogen (in the form of urea) needs only 0.05 l of water. In other words, just 10% of water needed for ammonia excretion is enough for urea excretion.[9]

Urea, a less toxic nitrogenous waste, is derived from ammonia. It is the liver which detoxifies ammonia by combining it with carbon dioxide (another waste product of metabolism) to produce urea.[10]

On the other hand, the excretion of urea takes place through either the kidneys or the skin. Here both the skin and the kidneys are excretory organs.[11]

  • Disposing of Uric Acid:

    Among the nitrogenous waste products of metabolism, uric acid is the least toxic substance. It is also only slightly soluble in water. Your body can store it in the cells and the tissues without the risks of toxicity and interference with osmoregulatory processes.

Do you know the excretion of uric acid requires only a small amount of water? For the excretion of 1 g of nitrogen (in the form of uric acid), just 0.001 l water is needed. In other words, the removal of uric acid needseven less than 1% of the water required to excrete an equivalent amount of nitrogen in the form of ammonia.[12]

Humans are not urecotelic (excreting uric acid as the major nitrogenous waste), but uric acid is produced in the body. It is produced as a result of the nucleotide breakdown in the liver. The excretion of uric acid is accomplished by the kidneys.[13]

  • Excretion of Carbon Dioxide:

    Disposing of carbon dioxide falls in the domains of both the respiratory system and excretory system. In other words, this task of the excretory system is handed over to the respiratory system for execution.

Carbon dioxide is a by-product of respiration, producedduring the breakdown of glucose in cells. It is produced in large amounts by cellular processes. Approximately 200ml/minute or 15,000 to 20,000 mmolof CO2 is produced each day in your body. Accumulation of this gas is a great influence on the pH level of the blood. On the other hand, your body is constantly striving to maintain equilibrium by balancing the pH of blood and ECF (extra cellular fluid).[14]

Blood collects carbon dioxide from tissues and transports it to the lungs for excretion. On reaching the lungs through the pulmonary artery, the blood passes across the capillary membranes of alveoli where carbon dioxide diffuses from the capillary into the alveolar sacs. The gas is then excreted through exhalation.[15]

So, produced during the breakdown of glucose in the cells, carbon dioxide is excreted with the help of blood and lungs. Here the lungs act as excretory organs.[16]

  • Getting Rid of Excess Water

    You drink water or other fluids as you feel thirsty. The thirst is induced by the body for the intake of the required amount of water. The intake of water also takes place through food. Meanwhile, it is also produced by cellular processes during the breakdown of glucose. An excess of water is harmful for the body. So, the excess of it should be excreted out of the body.

The kidneys, the skin and the lungs act as excretory organs for the removal of water out of the body.[17]

  • Removal of Inorganic Ions

    Certain inorganic ions enter the body through food and water. Here it should be made clear that the ions are not a metabolic waste product like ammonia, urea, carbon dioxide, water, bile pigments, and urochrome. However, the excess inorganic ions are to be removed to maintain a constant level in the body.

The kidneys and the sweat glands take part in the excretory process of the inorganic ions.[18]

  • Excretion of Bile Pigments

    The bile pigments form another metabolic waste of great significance. They are produced as a result of the breakdown of hemoglobin of RBCs (Red Blood Cells) in the liver. Unlike the nitrogenous waste products, these pigments are not excreted through the urinary system. Rather, the liver transfers them to the gallbladder which empties them into the small intestine. So, the bile pigments are excreted with feces.[19]

  • Excretion of Urochrome

    Just like bile pigments, urochrome is produced as a result of the breakdown of hemoglobin in the liver. It is a water-soluble pigment of yellow color. After its production, it is dissolved in the blood and passed on to the kidneys for its ultimate excretion with urine. Do you know it is the presence of urochrome which gives a yellow color to the urine?[20]

  • Storage of Waste

    In addition to the collection and elimination of the waste products, certain organs of the excretory system are also specialized for the temporary storage of solid and liquid waste, such as the rectum and the urinary bladder.

The rectum serves as the temporary storage for undigested semi-solid mass while the urinary bladder is the place for the short-term storage for liquid waste. Such specialized parts of the excretory system are almost indispensable for a healthy lifestyle and the success of advanced social and highly civilized behavior among humans.

The processes of bothurination and discharge of feces are under your voluntary control. So, you can hold the wastes in place till the time you reach a place that is, especially, meant for excretion, such as toilet or lavatory.

  • Detoxification of Harmful Substances:

    As you know, the metabolic processes produce different kinds of poisons, toxins and other harmful substances. They need to be partially or completely neutralizedin in order to save your body from serious damages.

For example, a nitrogenous waste product of metabolic processes, ammonia, is a highly toxic chemical. It is extremely soluble in water and can cause serious damage to the tissues. An increase in the concentration of ammonia may also affect the supply of blood to the brain as well as the synaptic transmission.[21]

So, highly toxic ammonia should be converted into less toxic urea. The organ of your excretory system that is assigned such an important duty is the liver. It converts extremely toxic ammonia into a mild or less dangerous compound, called urea. In this way your delicate and sensitive internal body organs are saved from the imminent damage of these poisonous substances.

  • Maintenance of Homeostasis

    Homeostasis is the ability of the body to maintain a nearly constant and stable internal environment despite changes in the external environment.

It took millions of years for the sophisticated homeostatic mechanisms to evolve. Whileremoving different metabolic wastes and excess substances, the excretory system is actually striving to maintain a balanced internal environment in the body. So, it plays an important role in the maintenance of homeostasis.

The perfect maintenance of constant internal body environment, as opposed to fluctuations in the external environment, is very necessary not only for health but also for your very survival. For example, when you go out in the scorching heat of summer, more and more environmental heat tends to heat your body, thus drastically increasing the internal body temperature beyond optimum levels.

To safeguard your body against such extreme environmental conditions, the eccrine or sweat glands are triggered into vigorous action. The large quantities of sweat poured out of your body through small pores in the skin are meant for the initiation and continuity of the cooling mechanism.

The scientific principle, involved in this mechanism, is that, “evaporation causes cooling” because in this process high energy water molecules escape, leaving behind only low energy molecules that bring the considerable decrease in your body temperature.

  • Removal of Liquid Waste

    The elimination of liquid waste out of your body is accomplished by two separate mechanisms, namely, urination (urine production and its discharge) and sweating.

The major organs involved in the discharge of liquid waste include kidneys, urethra, ureters, and urinary bladder. The liquid waste is secreted and collected in the kidneys, which is then transferred to the urinary bladder for temporary storage. From here, it is discharged out of the body by a voluntary action.

  • Removal of Gaseous Waste

    Gaseous waste is produced in the form of carbon dioxide (CO2) during different metabolic activities in your body, which is then expelled out of the body through exhalation. So, here it becomes obvious that your lungs play the role of an extremely important excretory structure. The accumulation of carbon dioxide, in your body, may result in severe consequence for your health as well as life.

  • Discharge of Seminal Fluid:

    Running along the entire length of male reproductive organ, the comparatively long urethra in human males is used not only for the discharge of urine but it also assists in the process of ejaculation. Ejaculation is, actually, a biological terminology which, particularly, refers to the discharge of seminal fluid (or semen) from the male reproductive organ during copulation.

The ejaculate has two main components, i.e.sperms and seminal fluid. Melman et al (2011), in their book “After Prostate Cancer: A What-comes-next Guide to a Safe and Informed Recovery” claim that only 1% of what the human males ejaculate is sperms while the remainder 99% is semen (seminal fluid). The semen is secreted by two glands, namely, the prostate and seminal vesicles. The nutrients and enzymes present in the seminal fluid are used to keep the sperm alive and mobile, so they are able to fertilize an egg.[22]

How Excretory System Works

Without a feedback based control mechanism, the excretory system may perform some of its jobs, but it won’t be able to maintain a stable internal environment. When you look at the functioning of different excretory organs, there seems to be an efficient control system coordinating and regulating different activities.

Hormonal Control of Urinary System:

The pituitary gland, located below the brain, controls the filtering action of the kidneys. Measuring about the size of a pea, the pituitary gland is also a part of the endocrine system. It secretes and releases hormonal substances which affect the ability of the kidney to filter excess water from the blood.[23]

The pituitary gland releases a hormone, called antidiuretic hormone or ADH which controls the absorption of water back into the blood. Controlling the ability of the body to hold onto water is one of the most important jobs of antidiuretic hormone.

For example, if you do not drink enough water, ADH will be released and cause the kidneys to remove more water from the urine. As a result, the urine will become more concentrated and less in volume.[24]

Body Fluid Regulation:

Your kidneys are always busy in producing urine by filtering waste products from the urine. The amount of urine to be produced by the kidneys is determined by the amount of fluid in the body. As water is lost through urination, sweating and breathing, you need to drink water and other fluid to compensate for that water loss. The water you drink ends up circulating in the blood as the plasma content of the blood is mostly water.

The kidneys normally adjust themselves to the amount of water a person drinks. For example, if you suddenly increase the intake of water, your kidneys will produce more diluted or watery urine. On the other hand, if you drink much less fluid than usual, the urine will be more concentrated and less in volume.[25]

Gaseous Transport and Excretion:

The transport and excretion of carbon dioxide involves the mechanism of gaseous exchange. It is because as oxygen enters the blood from the alveolar sacs, carbon dioxide moves in the reverse direction, i.e. from blood to alveolar sacs.

There are two points for the exchange of respiratory gases, viz. the lungs level and the cellular level. Atthe level of the lungs, oxygen enters the blood and carbon dioxide leaves for its excretion through exhalation. As the air you inhale reaches the alveoli, the Type 1 cells of epithelium allow for the exchange of gases to occur. There are millions of alveoli which create a total surface area of around 130 square feet. Moreover, lying along and embedded among the blood capillaries, the alveolar sacsserve to create an air-blood interface.[26]

At the cellular or tissue level, there occurs the diffusion of oxygen into the cells or tissues from the blood. Meanwhile, moving in the opposite direction, carbon dioxide diffuses to the blood from the tissues. As a waste product of respiration (or metabolism), carbon dioxide is transported by the blood to the lungs for excretion.[27]

Excretory System Parts

For the performance of a plethora of jobs assigned to it, the excretory system has to get help from multiple organ systems. Therefore, several different organs are involved in the excretion of different harmful or excess substances from the body. The lungs, actually the parts of the respiratory system, also act as excretory organs.

Skin, the largest external organ, forms a protective layer around the body and serves as an organ for touch. At the same time, it also plays an important role in the excretion of certain substances. The blood, an integral component of the cardiovascular system (where the heart is the pumping organ), serves the additional job of transporting the waste gas, carbon dioxide, from the tissues to the lungs for its excretion.

Though more than a dozen organs of the body take part in the excretory processes, the major ones are being described as under:

  • The Lungs:

    According to Alters, S. (2000), the lungs and the kidneys are the primary organs of excretion. On the other hand, the liver, the large intestine, and the skin play a minor role in the disposal of the metabolic wastes out of the body. The lungs are involved with the excretion of carbon dioxide and water in the form of vapors.[28]

In addition to the removal of carbon dioxide, the lungs also help in the excretion of several other substances, including water and certain volatile substances, like the ether, alcohol vapors and chloroform vapors, etc.[29]

  • The Kidneys:

    While liver is your body’s refinery, the kidneys help in the maintenance of the delicate balance of fluids in the body, filtering out toxins and the regulation of the acid and electrolytes content. As the body’s natural filtering system, the kidneys keep your body healthy and prevent it from poisoning itself.[30]

Functioningas the major excretory organs in all vertebrates, the kidneys assist in the elimination of nitrogenous waste (in the form of urine), maintenance of the water balance of the body (osmoregulation) and regulation of the concentration of the hydrogen ions in the body (Iso-ionia).[31]

Produced as the result of the deamination of amino acids, almost all of the ammonia is efficiently captured by the liver to make urea from it. The liver releases the urea to the blood. As the blood passes through kidneys, they clear all the urea from the blood for its excretion in the form of urine. [32]

The division of labor between the liver and the kidneys also allows easy diagnosis of the diseases of both the organs of the body. Here it is noteworthy that urea is body’s principal vehicle for the excretion of unused nitrogen. For example, high level of blood ammonia is a sign of the liver diseases. On the other hand, the kidney disease can be diagnosed through a high level of urea in the blood.[33]

  • The Skin:

    Basically, skin is a part of the integumentary system but its role as an excretory organ is also of great significance. Subburaj (2004), in the book “Basic Facts of General Knowledge”, claims that skin and kidneys are two main organs of the excretory system. The skin is also the largest external organ and protective cover of the entire body.

Meanwhile, the skin also acts as an organ of sense or touch and helps in the regulation of the body temperature. While working as an excretory system organ, it throws out the nitrogenous waste products in the form of sweat.[34]

Urea (derived from ammonia) and water are excreted through either kidneys or skin. At the same time, certain inorganic ions are also removed through the skin.[35]

  • The Liver:

    Functioning in the capacity of an excretory organ, the liver detoxifies an extremely toxic chemical, ammonia, which is produced during the catabolism of proteins and nucleic acids.

In addition to detoxification, the liver also assists in the excretion of bile pigments (produced during the breakdown of hemoglobin in the liver). The bile pigments are emptied into the small intestine after passing through the gall bladder.

The liver carries out the deamination (removal of amine group) of amino acids to produce ammonia. Being highly toxic to the body tissues, the ammonia is then converted to less toxic substance, urea. The liver also serves as the site for the breakdown of nucleotides and hemoglobin.[36]

  • The Blood:

    If blood does not transport carbon dioxide, how will this gas be transported to lungs for excretion?According to Chiras (2003), the blood accounts for about 8% of the total body weight. An individual, weighing 70 kilograms, has 5 to 6 liters of blood in the body. It is made up of plasma (55% by volume) and red blood cells, white blood cells and platelets (45%). [37]

The circulatory fluid in the circulatory or cardiovascular system, the blood also assists other body systems, like respiratory system and excretory system, in the execution of their jobs. In the role of an excretory organ, it collects carbon dioxide from tissues and transports them it to lungs for removal out of the body.[38]

  • The Bladder:

    A hollow muscular structure and largely a pelvic organ, the urinary bladder acts as a reservoir as its main function in the excretory system. When empty, it can be seen lying behind the symphysis pubis. However, when full, it rises above the level of symphysis and can be palpated readily.[39]

When empty, the bladder is distinguishable into the parts, like the apex, the neck, the base and two anterolateral or infralateral surfaces. The divisions of the autonomous nervous system provide rich innervation to the bladder. The sympathetic nerves originate from the upper lumber and lower thoracic segments.[40]

Temporary storage and elimination of the urine are the two major functions of the urinary bladder. When filled with urine, the bladder assumes a pear shape and can hold almost a quart of urine. It receives the urine through two tubes, called ureters. During urination, the bladder empties into a tube, called the urethra.[41]

  • The Ureters:

    There are two ureters in your body each one descending from the pelvic region of a kidney.Each ureter can basically be called an extension of the pelvis of your kidney that extends around 10 to 12 inchesdown to reach the urinary bladder. Beginning as the funnel shaped pelvis, each ureter descends parallel on each side of your vertebral column and connects to the bladder posteriorly. [42]

The transportation of urine from the renal pelvis to the bladder is the principal function of the ureters. The smooth muscular walls of the ureters produce peristaltic contractions to carry the urine from the kidneys to the bladder. Meanwhile, the hydrostatic pressure and gravity also contribute to the transportation of the urine.[43]

  • The Urethra:

    The urethra is a tubular structure which is connected withthe bladder and helps in the process of urination. The urethra leads from the underside of the urinary bladder to the outside of the body. In men, this tube also acts a part of the reproductive system. In this case, it is used to carry the seminal fluid (semen) to the outside of the body during ejaculation.[44]

However, in women, there is no connection between the reproductive and urinary systems.Secondly, the urethra is much shorter and located closer to the rectum and its associated bacterial population in women. This is the reason that women are better able to control the infections of the urinary tract and bladder than men.[45]

  • The Large Intestine:

    Continuous with around 21 feet long and 1 inch wide small intestine, the large intestine is also referred to as the bowel. It extends for about 5 feet in length and measures around 2.5 inches in diameter. So, the bowel is two and a half times wider than the small intestine. [46]

The extensions of the visceral peritoneum of the large intestine, called mesocolon, attach it to the posterior wall of the abdomen.The pouchlike cecum, the colon, the rectum and the anal canal are the four principal regions of the bowel.[47]

The absorption of fluid (water), the synthesis and absorption of certain vitamins are the functions of the large intestine. However, as an excretory organ, the main job of the bowel is the formation and elimination of the feces.[48]

  • The Rectum:

    As described by Rizzo, D. C. (2015), in the book “Fundamentals of anatomy and physiology”, the rectum is actually one of the four principal regions of the large intestine. Measuring about 7 to 8 inches in length, it forms the last segment of the gastrointestinal tract. The rectum is located anterior to the bones ofsacrum and the coccyx. It terminal part is called the anal canal which is about 1 inch in length.[49]

The primary job of the rectum is to collect feces and contribute to the process of defecation. The desire for defecation is associated with the start of the mandatory contractions in the rectal region.[50]

Two types of sphincters are involved in the process of defecation.The smooth muscle sphincter guarantees the major part of the continence while the striated muscle sphincter contributes a complementary action in case of the urgent need.[51]

  • The Anus:

    The anus is the posterior most part of the gastrointestinal tract (which begins at the mouth) and it serves as an opening for the anal canal to the exterior. Measuring about 1 inch in length, the anal canal is the terminal part of the rectum. The anal aperture is guarded by two sphincters which control and regulate the passage of feces during defecation.

The external sphincter is made up of the skeletal muscle while the internal one is composed of smooth muscle fibers.[52]

Excretory System Diseases

The disorders of the excretory system are specifically related to the malfunctioning of the kidneys, urinary bladder, ureters, urethra, large intestine, rectum and anus. Though the lungs and the skin also serve as excretory organs, their diseases are usually grouped among the respiratory system disorders and the integumentary system disorders, respectively.

Some of the excretory system disorders are described below along with their diagnostic symptoms and common remedies.

  • Kidney Stones

Formed on the inner surface of the kidneys, the kidney stones or renal calculi are the solid pieces of materials composed of mineral crystals. The stones result from the precipitation of the substances dissolved in urine. The presence of certain substances at higher concentrations than normal increase the likelihood of kidney stone formation.

Though stones can form from any material, 80% of all the kidney stones result from precipitation of calcium in the urine. Uric acid, cystine and magnesium ammonium phosphate (struvite) are some of the other common stone compositions.

A personal history of kidney stones poses the highest risk for the formation of renal calculi. Metabolic disorders, genetic diseases and unhealthy dietary habits are some of the other risk factors for the disease. However, a family history of kidney stones, recurrent urinary tract infections and certain medications, like calcium based antacids and diuretics, also serve as the risk factors for the development of the disease.[53]

  • Symptoms/Diagnosis

The passage and migration of stones from the kidneys to the ureters gives rise to the symptoms. As described in the Encyclopedia of Diseases and Disorders (2011), the signs and symptoms of the kidney stones development include:

  • Intense pain in the lower abdomen, back or groin (often requiring hospitalization).
  • Renal colic (pain associated with stones) occurring in paroxysms for up to an hour.
  • Presence of blood in the urine.
  • Experiencing pain during urination and a frequent sensation of needing to urinate.
  • Nausea and vomiting.
    • Treatment

Effective medical and surgical therapies are available for managing kidney stones and preventing recurrence. The diagnosis can be carried out through clinical symptoms, and radiological imaging, like CT scanning, or ultrasound.

Pain killers are used to relieve pain. Shock wave lithotripsy is used for the removal of the stones. However, they can also be removed through the skin or by the use of an endoscope.[54]

As the patents with the personal history of the kidney stones are at the highest risk of the recurrence of the disease, they need to be very careful. Its prevention requires medications, changes in diet and drinking lots of fluids.[55]

  • Bladder Cancer

According to Mallory (2005), the cancer of bladder is the fourth most widespread type of carcinoma in men. On the other hand, in women, it is the eighth most common type of cancers.[56]

Bellmunt (2015) calls it an environmental disease on the basis of the observation that it shows geographic variation. Its incidence is higher in the old men than in the young individuals.

The risk factors for bladder cancer include tobacco smoking, water arsenic, occupational exposures, the infestation of Schistosoma haematobium and certain medications.[57]

  • Symptoms/Diagnosis

The following bladder cancer symptoms, as highlighted by James (2006) will help in the diagnosis of the disease:

  • Hematuria or blood in the urine.
  • Gross hematuria or too much blood in the urine which turns it pink or red.
  • Frequent urination.
  • Urinary urgency which is the feeling of sudden, strong desire to urinate.
  • Low urine output due to obstruction in ureteral orifices.
  • Feeling of a mass in the lower abdomen.
  • Kidney failure. [58]
    • Treatment

Different therapies may be suggested for the treatment of metastatic and invasive types of bladder cancer. The metastatic bladder cancer is usually very difficult to treat. Aggressive chemotherapy is used for cancer that has spread outside of the bladder. Mostly, a combination of four drugs (cisplatin, Adriamycin, vinblastine and methotrexate) is given (James, 2006).[59]

In case of invasive bladder cancer, the treatment should be sought right away to prevent its spread outside of the bladder. Surgery can be a solution only if all of the cancer is removed.[60]

  • Urethritis

Do you know urethritis is one of the most common genitourinary infections affecting both men and women? Urethritis is characterized by the inflammation of the urethra which is the tube that drains the urine.

Mostly,the sexually transmitted diseases are the cause of urethritis. The infection is caused by either chlamydia or gonorrhea.[61]

  • Symptoms/Diagnosis

Muma, R. D., & Lyons, B. A. (2011) list the following diagnostic symptoms of urethritis:

  • Frequent urination during the daytime as well as nighttime.
  • Urinary urgency and difficulty in urination.
  • Urethral discomfort caused by walking.
  • Abnormal vaginal bleeding.
  • Urethral discharge of yellowish green color (gonococcal infection) or clear (non-gonococcal infection).
    • Treatment

In case of both gonococcal and non-gonococcal urethral infections, an appropriate antibiotic therapy may be administered to the patients. The treatment is generally a single dose regiment and it should be started immediately.[62]

Excretory System Facts

  1. Do you know water is also produced as a metabolic waste in the body through the breakdown of glucose?[63]
  2. Is skin also an organ of the excretory system? Water produced as a metabolic waste is removed through the kidneys, the lungs and the skin.[64]
  3. Children are unable to control urination until they reach the age of 2 to 3 years.[65]
  4. When you take high-protein diet (say, 100g/day or more) you must drink plenty of water to excrete urea and avoid the risk of dehydration.[66]
  5. A large amount of carbon dioxide, around 200ml/minute, is produced by cellular processes.[67]
  6. Do you know only 1% of the ejaculate (fluid released during ejaculation) is sperm while the remainder 99% is the semen or seminal fluid.[68]
  7. When you do not drink enough water, the antidiuretic hormone (ADH) is released by the pituitary gland which causes the filtering organs (the kidneys) to remove more water from the urine. So, the urine will be more concentratedand less in volume.[69]
  8. As an excretory organ, the skin contains sweat glands which help in the elimination of urea and inorganic salts along with water.[70]
  9. While working in the capacity of an excretory organ, the skin helps in the regulation of body temperature by producing sweat which evaporates and causes cooling.[71]
  10. The kidneys adjust to the amount of water you drink. If you drink more water, they will produce more diluted or watery urine and vice versa.[72]
  11. Working in coordination with the liver, the lungs and buffers, the kidneys play an important role in the acid-base balance in the body.[73]
  12. As an endocrine gland in the body, the kidneys secrete the hormones, like renin, calcitriol and erythropoietin.

Here renin influences blood pressure, calcitriol affects calcium balance and erythropoietin stimulates the production of erythrocytes.[74]

  1. Do you know chronic renal failure leads to the signs of anemia? It is because renal failure causes a decrease in erythrocyte production.[75]
  2. In addition to the elimination of the waste products of metabolism, the kidneys also excrete foreign substances, like drugs, pesticides and other harmful chemicals that are ingested in food. [76]
  3. On average, the urinary bladder can hold 700 to 800 ml or almost a quart of the urine.[77]
  4. When the bladder is filled less than half, the stretch receptors in its walls send a message to the brain which induces the desire to urinate.[78]
  5. In addition to the formation and expulsion of feces, the large intestine also syntheses three important vitamins, namely, vitamin K, biotin and vitamin B5.

These vitamins are synthesized by the bacteria in the colon. Vitamin K, biotin and vitamin B5 are used for blood clotting, glucose metabolism and the synthesis of certain neurotransmitters and hormones, respectively.[79]

  1. Do you know 80% of all the kidney stones are composed of calcium?[80]
  2. Ammonia, urea and uric acid are the toxic nitrogenous wastes produced in your body as the result of catabolic reactions.[81]
  3. As a metabolic waste, ammonia is more toxic than urea and your body needs more water for its elimination.[82]
  4. Your body needs a large volume of water, around half a liter, to eliminate just 1g of nitrogen in the form of ammonia.[83]
  5. Surprisingly, only 0.05 liter is enough to excrete 1g of nitrogen in the form of urea. In other words, 10% of water required for ammonia excretion is enough for excretion of urea![84]
  6. The excretion of 1 g of nitrogen in the form of uric acid needs just 0.001 l of water. In other words, in case of uric acid, only less than 1% water is required to excrete an equivalent amount of nitrogen in the form of ammonia.[85]
  7. Urea is the most toxic nitrogenous waste in the body and it is highly soluble in water.[86]
  8. Uric acid is the least toxic nitrogenous waste with very low solubility in water.[87]
  9. The animals excreting ammonia, urea and uric acid as the principal nitrogenous waste are termed as ammonotelic, ureotelic and urecotelic, respectively.[88]
  10. Are you ureotelic? Certain bony fish, cartilage fish, adult amphibians and mammals (including humans) are ureotelic.[89]


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