Urinary System: Function and Organs

Urinary System Function

• Maintains blood salts, water, and pH.
• Excretes metabolic wastes via urine.
• Metabolic wastes are by-products of normal cell and tissue activities.

Major Organs

• Kidneys
• Ureter
• Bladder
• Urethra

Excretion of Metabolic Wastes

• Human metabolic waste contains mostly nitrogen compounds.
• Examples of metabolic waste: urea, creatinine, ammonium, and uric acid.
  • Urea is a waste product of amino acid metabolism and the primary waste product in urine, and is secreted by the kidneys.
  • Ammonia comes from the liver, breaks down amino acids, and is secreted by the liver.
  • Creatinine & uric acid come from the breakdown of creatine and other amino acids, and are secreted by the liver.

Kidney Functions

• Water and salt balance is a key function.
• Sodium (Na) and Potassium (K) are removed from the blood to regulate blood pressure.
• Regulate the acid-base balance of the blood.
• Filters 180 liters of blood daily.
• Filtration occurs through nephrons.
• Nephrons interact with arteries to filter blood and maintain blood pH.
• This function is done via the renal vein & artery
• Healthy blood pH is 7.4.

Hormone Secretion by Kidneys

• The kidneys also work in the endocrine system by releasing aldosterone and producing EPO.
• Kidneys release renin, an enzyme, that leads to the release of aldosterone by the adrenal glands.
• Aldosterone regulates the water salt balance of the blood.
• Adrenal glands are located on top of the kidneys.
• EPO is a hormone that regulates red blood cell production.

Ureters

• Move of urine from the kidneys to the bladder.
• Small, muscular tubes that are 25cm (9.84in) long and 5mm (.2in) wide.
• Ureters contain three layers.
  • Inner mucus membrane.
  • Smooth muscle layer.
  • Outer fibrous connective tissue.
• Peristalsis causes urine movement to the bladder from the kidneys.

Bladder

• Bladder is a storage container for urine.
• Contains three openings; two for the ureters, and one for the urethra.
• The bladder wall is expandable because of its three layers of smooth muscle.
• Can hold 700-900 mL of urine.
• Contains mucus that lines the walls and prevents backflow.
• Two sphincters control urine flow into the urethra; one is voluntary, and one is involuntary.

Urethra

• A small tube that extends from the bladder to an external opening.
• Functions in removing urine from the body.
• Male urethras are part of the reproductive system and transport semen as well as urine.
• Female urethras are separate from the reproductive system.

Urinary System Disorders

• Illnesses such as diabetes, hypertension, and heart disease can exacerbate urinary disorders.
• Kidney stones consist of hard granules made of calcium, phosphate, uric acid, and protein.
  • Kidney stones form in the kidneys and may pass unnoticed, but can block and destroy nephrons.
• Uremia occurs when kidney stones destroy ²⁄₃ of the kidney's nephrons.
  • Causes waste buildup in the blood.
  • Causes retention of water and salts, leading to edema.
  • Edema is fluid accumulation in the tissues, which can lead to heart failure.

Hydration and Performance

• Water is 60-70% of a person's body weight.
• Intracellular water is inside of cells.
• Extracellular water is outside of cells.
• Dehydration can occur in both intracellular and extracellular fluids.

Intracellular and Extracellular Dehydration

• Intracellular dehydration is the loss of fluid from inside the cell, leading to water leaving the cell and entering the extracellular fluid.
  • Cells look shriveled, and organelles may not function correctly.
• Extracellular dehydration is loss of fluid from the extracellular space and blood, it is caused by diuretic use.
• Both intracellular and extracellular dehydration are dangerous.

Hydration Levels

• Dehydration means there is a loss of fluid from either within or outside cells.
• Dehydration leads to decreased performance, sickness, and death.
• Hydration can be measured by assessing urine color, urine specific gravity, or consistency of saliva.
• Greater than 2% dehydration can impair aerobic and potentially anaerobic performance.
• A dehydration level of 1% can impair children.
• Fluid loss through sweat can increase heat storage, heart rate, decrease stroke volume, and increase perceived effort.
• Fluid loss is often higher in people with higher body weights and/or surface areas.

Maintaining Hydration

• Start training in a euhydrated state with normal electrolyte levels via checking urine color.
• Consume sports drinks that contain 460mg of electrolytes per liter and carbs while training.
• After exercise, consume 150% of lost weight within six hours.