Excretory System

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Introduction

If you exercise on a hot day, you are likely to lose a lot of water in sweat. Then, for the next several hours, you may notice that you do not pass urine as often as normal and that your urine is darker than usual.
Do you know why this happens? Your body is low on water and trying to reduce the amount of water lost in urine. The amount of water lost in urine is controlled by the kidneys, the main organs of the excretory system.

Excretion

Excretion is the process of removing wastes and excess water from the body. It is one of the major ways the body maintains homeostasis.
Although the kidneys are the main organs of excretion, several other organs also excrete wastes.
They include the large intestine, liver, skin, and lungs. All of these organs of excretion, along with the kidneys, make up the excretory system.
The roles of the other excretory organs are summarized below:

The large intestine eliminates solid wastes that remain after the digestion of food.
The liver breaks down excess amino acids and toxins in the blood.
The skin eliminates excess water and salts in sweat.
The lungs exhale water vapor and carbon dioxide.

Urinary System

The kidneys are part of the urinary system, which is shown in Figure below.
The main function of the urinary system is to filter waste products and excess water from the blood and excrete them from the body.

Kidneys and Nephrons

The kidneys are a pair of bean-shaped organs just above the waist. A cross-section of a kidney is shown in Figure below.
The function of the kidney is to filter blood and form urine.
Urine is the liquid waste product of the body that is excreted by the urinary system. Nephrons are the structural and functional units of the kidneys.
A single kidney may have more than a million nephrons!

Filtering Blood and Forming Urine

As shown in Figure below, each nephron is like a tiny filtering plant. It filters blood and forms urine in the following steps:
Blood enters the kidney through the renal artery, which branches into capillaries. When blood passes through capillaries of the glomerulus of a nephron, blood pressure forces some of the water and dissolved substances in the blood to cross the capillary walls into Bowman’s capsule.
The filtered substances pass to the renal tubule of the nephron. In the renal tubule, some of the filtered substances are reabsorbed and returned to the bloodstream. Other substances are secreted into the fluid.
The fluid passes to a collecting duct, which reabsorbs some of the water and returns it to the bloodstream. The fluid that remains in the collecting duct is urine.

Excretion of Urine

From the collecting ducts of the kidneys, urine enters the ureters, two muscular tubes that move the urine by peristalsis to the bladder (see Figure above). The bladder is a hollow, sac-like organ that stores urine.
When the bladder is about half full, it sends a nerve impulse to a sphincter to relax and let urine flow out of the bladder and into the urethra.
The urethra is a muscular tube that carries urine out of the body. Urine leaves the body through another sphincter in the process of urination.
This sphincter and the process of urination are normally under conscious control.

Kidneys and Homeostasis

The kidneys play many vital roles in homeostasis. They filter all the blood in the body many times each day and produce a total of about 1.5 liters of urine.
The kidneys control the amount of water, ions, and other substances in the blood by excreting more or less of them in urine.
The kidneys also secrete HORMONES that help maintain homeostasis. Erythropoietin, for example, is a kidney hormone that stimulates bone marrow to produce red blood cells when more are needed.
The kidneys themselves are also regulated by hormones. For example, antidiuretic hormone from the hypothalamus stimulates the kidneys to produce more concentrated urine when the body is low on water.

Kidney Disease and Dialysis

A person can live a normal, healthy life with just one kidney. However, at least one kidney must function properly to maintain life.
Diseases that threaten the Health and functioning of the kidneys include kidney stones, infections, and diabetes.
Kidney stones are mineral crystals that form in urine inside the kidney. They may be extremely painful. If they block a ureter, they must be removed so urine can leave the kidney and be excreted.
Bacterial infections of the urinary tract, especially the bladder, are very common. Bladder infections can be treated with antibiotics prescribed by a doctor. If untreated, they may lead to kidney damage.
Uncontrolled diabetes may damage capillaries of nephrons. As a result, the kidneys lose much of their ability to filter blood. This is called kidney failure.
The only cure for kidney failure is a kidney transplant, but it can be treated with dialysis. Dialysis is a medical procedure in which blood is filtered through a machine.

The urinary system is a vital system in the body that helps to remove waste products and toxins from the blood. It consists of two kidneys, two ureters, a bladder, and a urethra.

The kidneys are two bean-shaped organs that are located in the lower back, just above the waist. They are responsible for filtering the blood and removing waste products, such as urea, creatinine, and uric acid. The kidneys also help to regulate blood pressure, produce red blood cells, and maintain the body’s fluid balance.

The ureters are two tubes that carry urine from the kidneys to the bladder. The bladder is a muscular sac that stores urine until it is time to urinate. The urethra is a tube that carries urine from the bladder out of the body.

The urinary system works by filtering the blood and removing waste products. The kidneys contain millions of tiny units called nephrons. Each nephron has a glomerulus, which is a Network of capillaries that filters the blood. The glomerulus is surrounded by Bowman’s capsule, which collects the filtered blood. The filtered blood then flows into the proximal convoluted tubule, where it is further processed. The proximal convoluted tubule leads to the loop of Henle, which is a U-shaped structure that helps to concentrate the urine. The loop of Henle leads to the distal convoluted tubule, where the urine is further processed. The distal convoluted tubule leads to the collecting duct, which carries the urine to the bladder.

Urination is the process of emptying the bladder. When the bladder is full, it sends a signal to the brain that it is time to urinate. The brain then sends a signal to the muscles in the bladder to contract, which forces the urine out of the bladder and through the urethra.

Urine is a waste product that is produced by the kidneys. It is a clear, yellow liquid that contains water, waste products, and electrolytes. The main waste products in urine are urea, creatinine, and uric acid. Urea is a waste product that is produced when the body breaks down proteins. Creatinine is a waste product that is produced when the body breaks down muscle tissue. Uric acid is a waste product that is produced when the body breaks down purines.

The kidneys are responsible for maintaining the body’s fluid balance. They do this by reabsorbing water from the urine. The kidneys also help to regulate blood pressure by secreting hormones that control the production of urine.

The kidneys are also responsible for maintaining the body’s acid-base balance. They do this by secreting Acids And Bases into the urine.

The urinary system is a vital system in the body that helps to remove waste products and toxins from the blood. It also helps to regulate blood pressure, produce red blood cells, and maintain the body’s fluid balance.

Here are some frequently asked questions and short answers about the excretory system:

What is the excretory system?
The excretory system is a group of organs that work together to remove waste products from the body.
What are the main organs of the excretory system?
The main organs of the excretory system are the kidneys, ureters, bladder, and urethra.
What are the functions of the excretory system?
The functions of the excretory system are to remove waste products from the blood, regulate blood volume and pressure, and produce urine.
How does the excretory system work?
The excretory system works by filtering the blood to remove waste products, which are then excreted in the form of urine.
What are some common problems with the excretory system?
Some common problems with the excretory system include kidney stones, urinary tract infections, and kidney failure.
How can I keep my excretory system healthy?
You can keep your excretory system healthy by drinking plenty of fluids, eating a healthy diet, and exercising regularly.
What are some signs and symptoms of problems with the excretory system?
Some signs and symptoms of problems with the excretory system include pain, blood in the urine, and changes in urination habits.
When should I see a doctor about problems with the excretory system?
If you have any of the signs or symptoms of problems with the excretory system, you should see a doctor right away.
What are the treatments for problems with the excretory system?
The treatments for problems with the excretory system vary depending on the specific problem. However, some common treatments include medication, surgery, and lifestyle changes.
What is the outlook for people with problems with the excretory system?
The outlook for people with problems with the excretory system varies depending on the specific problem. However, with proper treatment, most people with problems with the excretory system can live long and healthy lives.

The main function of the excretory system is to:
(A) remove waste products from the blood
(B) regulate blood pressure
(C) produce urine
(D) produce sweat
The kidneys are the main organs of the excretory system. They are located in the:
(A) abdomen
(B) chest
(C) head
(D) back
The kidneys filter waste products from the blood and produce urine. Urine is then transported to the bladder, where it is stored until it is excreted from the body.
The bladder is a muscular sac that stores urine. When the bladder is full, it sends a signal to the brain that it is time to urinate.
The urethra is a tube that carries urine from the bladder to the outside of the body.
The excretory system is important for maintaining homeostasis, or a stable internal Environment. Homeostasis is essential for life.
If the excretory system is not working properly, waste products can build up in the blood. This can lead to serious health problems, such as kidney failure.
There are a number of things that can affect the health of the excretory system, including:
(A) dehydration
(B) infection
(C) kidney stones
(D) all of the above
Dehydration can occur when a person does not drink enough fluids. This can lead to a build-up of waste products in the blood.
Infection can occur in the kidneys, bladder, or urethra. This can lead to inflammation and pain.
Kidney stones are hard deposits that can form in the kidneys. They can cause severe pain and can block the flow of urine.
There are a number of things that people can do to keep their excretory system healthy, including:
(A) drinking plenty of fluids
(B) eating a healthy diet
(C) exercising regularly
(D) all of the above
Drinking plenty of fluids helps to flush waste products out of the body.
Eating a healthy diet helps to prevent the formation of kidney stones.
Exercising regularly helps to keep the kidneys healthy.
If you have any concerns about your excretory system, it is important to see a doctor.