URINARY SYSTEM

The urinary system (or urinary tract) works as your body’s filtration system. When your
urinary system removes toxins and wastes from your body, it comes out as pee (urine). To be
able to pee, your body must pass this waste through a series of organs, ducts and tubes. If there’s
a problem at any step in this process, it can affect if you’re able to pee normally.
The urinary system consists of 4 major organs; the kidneys, ureters, urinary bladder and
the urethra. Together these organs act to filter blood, remove waste products, create urine and
transport urine out from the body.
The urinary system is also called the excretory system, because held within the urine are
the various excreted products, including by-products such as urea and uric acid, drugs, excess body
fluid and excess salts (electrolytes). These functions play an important role in maintaining
appropriate levels of water and salts (electrolytes) in the blood.

Urinary system organs

The organs of the urinary

system are the kidneys, ureters,
bladder and urethra. The kidneys
perform the filtration functions of the
urinary system and create urine,
while the remaining organs act as
transport tubes or provide temporary
urine storage. The anatomy of the
urinary system can be seen here in
the urinary system diagram.
KIDNEY

The kidneys are paired retroperitoneal organs located anterolateral to the spinal cord, near
the posterior body wall. They are roughly 12 cm in length and 6 cm wide, spanning from T12 to
L3 vertebral levels. The bean-shaped kidneys are somewhat protected by the lower rib cage, and by
a protective layer of perirenal fat. On their concave medial surface is the renal hilum, which is the
location where the ureters, blood vessels and nerves enter or exit the organ.

The most important blood vessels entering and exiting the kidneys are the renal
artery and renal vein. The adrenal glands sit on the superior pole of each kidney. Internally, the
kidneys consist of 2 layers; a highly vascularized outer renal cortex and an inner renal medulla.
Spanning across these two layers are millions of the kidneys’ functional units, the nephrons.

Nephrons are the filtering structure of the

kidney. They have two main parts, the renal
corpuscle and the renal tubule. The renal
corpuscle is a small ball of capillaries
(glomerulus) surrounded by a double layered
epithelial capsule (glomerular or Bowman's
capsule) similar to pushing your hand into a
balloon.
The renal tubule is formed by small
convoluted tubes which are closely associated
with blood vessels. Corpuscles are situated in the
renal cortex, while tubules dive into the medulla.
Water, electrolytes and waste products are
exchanged between the blood vessels and the
capsule/tubes of the nephrons by the process of both passive and active transport.
The products to be removed from the blood, or returned to the blood are very carefully
selected by these cells. Any liquid or chemical that remains in the nephrons’ tubes becomes urine.
The filtrate, or urine, gets carried out of the nephrons by collecting ducts, traveling through various
parts of the kidney before reaching the ureters.

URINARY BLADDER

The urinary bladder is a muscular sac whose function is to temporarily store urine. It is
located in the pelvis, just posterior to the pubic symphysis. Its walls consist of smooth
muscle which allows the bladder to stretch, permitting the bladder to store an increasing amount of
urine.
When distended with urine, the bladder sends a signal to the nervous system to initiate the process
of micturition (urination). In males, the neck of the bladder is surrounded by the prostate gland.
 The urethra is a single thin walled tube that carries urine from the bladder to outside of the
body. It is associated with two urethral sphincters, an internal smooth muscle (involuntary) urethral
sphincter and an external skeletal muscle (voluntary) urethral sphincter. The urethra differs
between sexes, with the female urethra being much shorter in length and the opening located
anterior to the vagina. The male urethra is longer as it travels the length of the penis, with the
opening located at the tip of the glans penis. The male urethra has the double function of both urine
and semen transportation.
Urinary System Function

The main function of the urinary system is to remove waste products from the body and
maintain water, electrolyte and acid-base (pH) balance in the blood. It does this through the
formation of urine. Waste products are filtered from the blood into the urine filtrate by nephrons.
Water, electrolyte and acid-base balance is a finely controlled process of filtration, reabsorption
and secretion, also occurring through nephrons.
The urinary system has a homeostatic relationship with many other body systems, by
which one or both rely on the other for effective functioning. For example the endocrine
system produces hormones such as antidiuretic hormone and aldosterone, which help to control the
kidney’s reabsorption of water and salts. This same water and salt balance is vital for the accurate
function of the muscular system, cardiovascular system and nervous system. Without appropriate
levels of sodium, potassium and calcium contraction of skeletal and cardiac muscle and the
function of nerves would be disrupted. Further, water and electrolyte balance in the body is
necessary for maintaining blood volume and blood pressure. While systemic blood pressure of the
cardiovascular system is responsible for driving the passive filtration of water and substances out
of the glomerulus into the glomerular capsule.
The urinary system has other endocrine functions too, with the kidney producing the
enzyme renin, the hormone erythropoietin and acting in the conversion of vitamin D. Our bodies
derive vitamin D either through diet or by skin synthesis when exposed to ultraviolet light. It is
then processed, firstly by the liver then by the kidneys, to transform it from its initial inactive
prohormone state into the active product of 1,25 vitamin D (calcitriol). Activated Vitamin D can
then be used by the body in various processes, including the absorption of calcium from the
gastrointestinal tract and the deposition of calcium into bone. Erythropoietin is produced by
specialized kidney cells, called interstitial cells, in response to tissue hypoxia. Low oxygen
situations such as anemia, living at high altitude or certain cardiac and pulmonary diseases will
result in tissue hypoxia. Erythropoietin acts on stem cells in bone marrow to increase red blood cell
production, this in turn results in more red blood cells circulating in our blood, carrying more
oxygen around the body and raising oxygenation of tissues. Renin is a hormone that plays a very
important role in blood pressure control, via the renin-angiotensin-aldosterone mechanism. Low
blood pressure, low sodium levels, or specific sympathetic nervous system activity stimulates
juxtaglomerular cells in the kidneys to produce renin.
Renin then acts like an enzyme on the plasma protein angiotensinogen, converting it to angiotensin
I. Angiotensin I has some vasoconstrictor properties but for the most part it leaves the kidneys and
enters the circulatory system to travel to the lungs. Here angiotensin I is converted to angiotensin II
by angiotensin converting enzyme. Angiotensin II has a number of functions; it is a strong
vasoconstrictor, it acts on the kidneys to decrease salt and water excretion and it stimulates the
production of aldosterone from the adrenal glands (which also decreases salt and water excretion).
All these actions individually result in increased blood pressure, acting together gives an enhanced
effect.

Conditions and Disorders Affecting the Urinary System

The urinary system plays a vital role in filtering waste, regulating fluid balance, and
eliminating toxins from the body. However, various conditions and diseases can affect the
kidneys, ureters, bladder, and urethra, leading to discomfort, infections, or life-threatening
complications. These disorders may be congenital (present at birth) or develop due to infections,
lifestyle factors, or underlying health conditions. Understanding these urinary system disorders is
essential for early diagnosis and effective management.

Urinary Tract Infections (UTIs) and Sexually Transmitted Infections (STIs)

Urinary tract infections (UTIs) are among the most common conditions affecting the
urinary system. They occur when bacteria, usually Escherichia coli (E. coli), enter the urinary
tract through the urethra and multiply in the bladder. UTIs can affect any part of the urinary tract,
including the kidneys (pyelonephritis), bladder (cystitis), and urethra (urethritis). Symptoms
include a burning sensation during urination, frequent urges to urinate, cloudy or strong-smelling
urine, and pelvic pain. Sexually transmitted infections (STIs), such as chlamydia and gonorrhea,
can also cause urinary symptoms, leading to urethritis and bladder discomfort. UTIs and STIs are
typically treated with antibiotics prescribed by a healthcare provider.
Kidney Stones

Kidney stones are solid deposits of minerals and salts that form in the kidneys due to
dehydration, high levels of calcium, oxalate, or uric acid, and certain metabolic disorders. These
stones can vary in size, from tiny grains to larger masses that obstruct the urinary tract. When
kidney stones move into the ureters (ureteral stones), they can cause severe pain, blood in the
urine (hematuria), nausea, and difficulty urinating. Small stones may pass naturally through
urine, while larger stones may require medical intervention, such as extracorporeal shock wave
lithotripsy (ESWL) to break them into smaller pieces or surgical removal in severe cases.

Urination Problems (Incontinence, Retention, and Overactive Bladder)

Urination problems can significantly impact a person's quality of life. Urinary

incontinence, or loss of bladder control, can result in urine leakage when coughing, laughing,
sneezing, or engaging in physical activity. Overactive bladder (OAB) causes a sudden and
frequent urge to urinate, often disrupting daily activities and sleep. Urinary retention occurs
when the bladder does not completely empty, leading to discomfort, urinary tract infections, and
increased bladder pressure. These conditions are often managed through behavioral therapies,
pelvic floor exercises, medications, or medical devices like catheters. In some cases, surgical
interventions may be necessary to improve bladder control.

Urinary Tract Obstructions

Urinary tract obstructions occur when a blockage prevents urine from flowing freely
through the urinary system. This can be caused by kidney stones, tumors, an enlarged prostate
(benign prostatic hyperplasia, BPH), pregnancy, or conditions such as Crohn’s disease. A
blockage in the ureters (ureteral obstruction) or bladder outlet obstruction can lead to painful
urination, difficulty urinating, and kidney damage if left untreated. Treatment options vary
depending on the cause and severity of the obstruction, ranging from medications to relieve
symptoms to surgical procedures such as stent placement or tumor removal.
Kidney Disease and Kidney Failure

Kidney disease is a serious condition that affects the filtering function of the kidneys.
Chronic kidney disease (CKD) is often caused by high blood pressure and diabetes, both of
which damage the blood vessels in the kidneys over time. As kidney function declines, waste
products build up in the bloodstream, leading to complications such as fluid retention, electrolyte
imbalances, and increased risk of heart disease. Symptoms of kidney disease include fatigue,
swelling in the legs, decreased urine output, and persistent itching. If kidney function deteriorates
to the point of kidney failure, dialysis or a kidney transplant may be required to sustain life.
Preventing kidney disease involves managing blood pressure, controlling blood sugar levels, and
maintaining a healthy lifestyle.

Interstitial Cystitis (Painful Bladder Syndrome)

Interstitial cystitis, also known as painful bladder syndrome, is a chronic condition that
causes bladder inflammation, leading to pelvic pain, frequent urination, and discomfort during
urination. Unlike bacterial UTIs, interstitial cystitis does not respond to antibiotics and has no
known cure. Its exact cause is unclear, but factors such as immune system dysfunction, nerve
abnormalities, or bladder lining defects may contribute to the condition. Treatment focuses on
symptom relief through medications, bladder training, physical therapy, and lifestyle
modifications such as avoiding irritants like caffeine and acidic foods.

Structural Problems and Congenital Defects

Some individuals are born with abnormalities in the urinary system that can affect normal
urine flow and bladder function. One such condition is an ectopic ureter, where the ureter does
not connect properly to the bladder, leading to urine leakage. Another example is vesicoureteral
reflux (VUR), where urine flows backward from the bladder into the ureters and kidneys,
increasing the risk of infections and kidney damage. In females, bladder prolapse (cystocele) can
occur, where the bladder drops into the vagina due to weakened pelvic floor muscles, often as a
result of childbirth or aging. Many of these structural issues require surgical intervention to
correct anatomical defects and restore normal urinary function.
What are common symptoms of urinary tract conditions?
Symptoms vary depending on what condition you have. Many conditions share similar
symptoms, like:

 Changes in how you pee. This could include many different symptoms like having to pee
more or less often and pain when you pee.
 Changes in your pee. This may include pee that’s brown, cloudy or contains blood.
 Pain in your abdominal region. Since most of your urinary organs are in your abdomen,
people with urinary issues may have pain, tenderness or feel pressure in that region of
their body.
 Fever, muscle aches and general unwell feeling. These could all be symptoms that
indicate infection. You may also experience nausea or vomiting.

Conclusion

The urinary system is susceptible to a wide range of disorders, from infections and
kidney stones to chronic conditions such as kidney disease and structural abnormalities. While
some urinary disorders can be managed with medications and lifestyle changes, others may
require surgical treatment to prevent complications. Early detection and proper medical care are
essential in maintaining urinary health and preventing long-term damage to the kidneys and other
parts of the urinary tract. If symptoms of urinary problems arise, seeking medical attention can
help diagnose and treat the condition before it leads to more serious health concerns.

Sources:

Urinary system. (2023, October 30). Kenhub.

https://www.kenhub.com/en/library/anatomy/urinary-system

Professional, C. C. M. (2025, February 7). Urinary System. Cleveland Clinic.

https://my.clevelandclinic.org/health/body/21197-urinary-system
 News-Medical. (2022, December 29). How does the urinary tract work?
https://www.news-
medical.net/health/How-Does-the-Urinary-Tract-Work.aspx