Urinary System Overview

Urinary System Overview

• The urinary system filters blood, removes waste and excess water, resulting in urine.
• It comprises the kidneys, ureters, bladder, and urethra.
• The system's primary function is to maintain normal body fluid volume and composition, and for excreting waste products and drugs.

Organs and Functions

• Kidneys: Filter blood and produce urine.
• Ureters: Tubes that transport urine from the kidneys to the bladder.
• Bladder: Stores urine until it is released from the body.
• Urethra: Tube that carries urine from the bladder to the outside of the body.

Common Urinary Issues

• Urinary tract infections (UTIs): Occur when bacteria enter the urinary tract through the urethra.
  • Can affect the kidneys, urethra, or bladder.
  • Treated with antibiotics.
• Kidney stones: Small masses formed by clumped waste products.
  • Can cause severe pain and block urine flow.
• Urinary incontinence: Loss of bladder control, leading to unintentional urine leakage.
  • Often exacerbated by coughing, laughing, sneezing, or jumping.
• Overactive bladder: Frequent and sudden urge to urinate.
• Urinary retention: Inability to completely empty the bladder.
• Growths or tumors: Can obstruct urine flow in any part of the urinary tract.
• Enlarged prostate: Can block the urethra, making urination difficult.
• Kidney disease: A common and serious condition affecting the urinary system.
  • Often caused by high blood pressure or diabetes.
  • Can lead to kidney failure.
• Painful bladder syndrome: Inflammation of the bladder, often treated with medications and physical therapy.
• Congenital abnormalities: Some babies are born with conditions affecting urinary tract formation.
  • Ex: ectopic ureter (ureter connects to a different location than the bladder)
• Bladder prolapse: Bladder drops into the vagina or hangs outside the vaginal opening.
  • May require surgery.

Symptoms and Diagnosis

• Many conditions have similar symptoms, including:
  • Pain or burning during urination.
  • Frequent urination.
  • Difficulty urinating.
  • Blood in urine.
  • Pain in the back or sides.
• Diagnosis involves assessment of symptoms and various tests, such as urine tests, blood tests, imaging scans, and cystoscopy.

Prevalence

• UTIs: More than 60% of women experience at least one UTI in their lifetime.
• Urinary incontinence: Over half of people who have given birth experience urinary incontinence.
• Kidney stones: Affect approximately 1 in 10 people.
• Chronic kidney disease: Affects 37 million people in the US.

Maintaining Urinary System Health

• Practice good hygiene.
• Maintain a healthy lifestyle.
  • Drink plenty of fluids.
  • Eat a healthy diet.
  • Manage weight.
  • Avoid smoking and excessive alcohol consumption.

Signs to Seek Medical Attention

• Difficulty or pain while urinating.
• Bloody urine.
• Frequent urination.
• Urinary incontinence.
• Pain in the back or sides.

Conclusion

• The urinary system is vital for maintaining overall health.
• Conditions affecting the system can significantly impact quality of life.
• Early diagnosis and treatment are crucial to prevent long-term complications.
• Prompt medical attention is essential for any urinary system concerns.

The Urinary System

• The Urinary system is responsible for maintaining the body's fluid volume and composition, and for excreting waste products and drugs.
• The Urinary system is composed of two kidneys, two ureters, the urinary bladder, and the urethra.

Kidneys

• Kidneys filter blood and produce urine
• Each kidney contains microscopic functional units called nephrons
• The nephron is the functional unit of the kidney, responsible for filtering blood and producing urine.
• The glomerulus is a network of capillaries within the nephron, where filtration takes place.

Blood Flow Through the Nephron

• Blood enters the nephron through the afferent arteriole.
• Blood exits the nephron through the efferent arteriole.
• The glomerular capillaries are surrounded by Bowman's capsule.
• Blood is filtered in the glomerulus, producing filtrate that passes into the Bowman's capsule.

Filtration

• Water and small molecules pass through the semipermeable walls of the glomerulus and glomerular capsule.
• Larger molecules and blood cells do not pass through during filtration.
• Filtration removes water and small molecules from the blood, leaving behind large molecules, blood cells, and plasma proteins within the capillaries.

Selective Reabsorption

• Takes place in the tubules of the nephron.
• Essential constituents needed by the body are reabsorbed back into the blood capillary.
• Active transport takes place at carrier sites in the epithelial membrane.
• Energy is needed to transport substances against their concentration gradients.
• The renal threshold refers to the concentration of a substance in the blood. If the renal threshold is exceeded, the substance will appear in the urine.
• For example, glucose is typically reabsorbed by the tubules, but hyperglycemia can exceed the renal threshold, resulting in glucosuria (glucose in the urine).

Hormones that regulate reabsorption

• Parathormone and calcitonin work together to regulate calcium and phosphate reabsorption.
• Antidiuretic hormone (ADH) increases water reabsorption by increasing the permeability of the convoluted tubules, resulting in concentrated urine.
• Aldosterone increases sodium reabsorption in the tubules, leading to increased excretion of potassium.
• Angiotensin II is a vasoconstricting hormone.

Tubular Secretion

• Some substances not required or in excess to body’s need may remain in blood after filtration due to speed of filtration, such as hydrogen ions and drugs like penicillin and aspirin.
• Substances in the blood that are filtered or not filtered, but are in excess in the body are actively secreted into the convoluted tubules.
• These substances are actively secreted into the convoluted tubules.
• Energy is needed for active secretion.

Urine Composition

• The final composition of urine depends on the amounts of water and solutes that are filtered, reabsorbed, and secreted.
• Urine is predominantly composed of water, urea and creatinine.

Water Balance

• The body gains water through liquids and food, and water is lost through urine, feces, perspiration, and expired air.
• The body regulates water balance through thirst and by adjusting the excretion of water in urine, mediated by antidiuretic hormone (ADH).

Electrolyte Balance

• Sodium and potassium are primary electrolytes in the body, ingested in food.
• Sodium and potassium balance is regulated by aldosterone, which controls their excretion in the urine.
• Calcium balance is ingested in food and is regulated by parathyroid hormone (PTH) and calcitonin.
• PTH acts on kidney tubules to reabsorb calcium.
• PTH increases calcium reabsorption from the kidneys, while calcitonin decreases calcium retention by the kidney.
• Aldosterone regulates the excretion of sodium.
• Calcitonin acts on kidney tubules to absorb less calcium.

Self Assessment

• Understand how the nephron filters the blood, including the different processes of filtration, reabsorption, and secretion.
• Explain how the urinary system maintains water balance and electrolyte balance.