Lecture Notes: The Urinary System

Functions of the Urinary System

• Removal of metabolic wastes from bodily fluids.
  • Urine contains metabolic wastes, unlike fecal matter which removes solid waste from the digestive system.
• Regulation of blood volume and blood pressure.
  • Kidneys secrete hormones to regulate based on blood flow and fluid levels.
• Regulation of plasma concentrations of electrolytes (e.g., sodium, potassium, chloride).
• Stabilization of blood pH.
  • Managing H+ ions and bicarbonate ions influences pH (normal blood pH = 7.4, slightly basic).
• Conservation of valuable nutrients.

Organs and Tissues of the Urinary System

• Kidneys

  • Bean-shaped organs located on either side of the spine.
  • Left kidney slightly higher than the right due to the liver.
  • Functions in filtering blood and creating urine.
  • Key structures: renal cortex, renal medulla, renal pyramids, major/minor calyxes, renal pelvis, and hilum.

• Ureters

  • Tubes that transport urine from kidneys to the urinary bladder.

• Urinary Bladder

  • Temporary storage organ for urine.

• Urethra

  • Tube that carries urine from bladder to outside.
  • Longer in males than females.

Kidney Structure and Function

• Blood Supply
  • Over 1 liter of blood flows through kidneys each minute.
  • Blood enters via renal arteries and exits via renal veins.
• Nephrons
  • Microscopic filtering units.
  • Components:
    • Glomerulus (capillary bundle)
    • Bowman's capsule
    • Proximal convoluted tubule (PCT)
    • Loop of Henle
    • Distal convoluted tubule (DCT)
    • Collecting duct

Urine Formation

1. Filtration: Blood pressure forces water and solutes across the glomerulus into Bowman's capsule.
2. Reabsorption: Vital nutrients reabsorbed from tubular fluid into blood.
3. Secretion: Waste products secreted into tubular fluid.

Components of Urine

• Primarily water (95%).
• Contains urea, creatinine, uric acid, and urochrome (gives yellow color).
• Urine is sterile when initially excreted.

Disorders and Conditions

• UTI (Urinary Tract Infection): More common in females due to shorter urethra.
• Kidney Stones: Hard deposits forming in kidneys, can be treated with sound waves.
• Dialysis: Needed in renal failure to filter blood externally.
• Kidney Transplant: Long-term solution for kidney failure, requires immunosuppressants.
• Glomerulonephritis: Inflammation due to antibody buildup affecting filtration.
• Incontinence: Loss of bladder control, common in elderly and during pregnancy.

Miscellaneous

• Peristalsis in ureters helps move urine to the bladder.
• Urinary reflexes trigger micturition (urination).