Study guide: Urinary System

📋 Course Outline

1. Excretion and Urinary Organs
2. Kidney Structure and Functions
3. Nephron and Urine Formation
4. Urine Composition and Disorders
5. Ureters, Bladder, and Urethra

📖 1. Excretion and Urinary Organs

★ Must-know

• The four organs of excretion are:

  • kidneys
  • sweat glands
  • lungs
  • intestines

• The urinary system consists of:

  • two kidneys
  • two ureters
  • the urinary bladder
  • the urethra

Further detail

📌 Renal refers to the kidney; renal physiology and nephrology concern kidney function, whereas urology concerns the urinary system.

📖 2. Kidney Structure and Functions

★ Must-know

• The kidneys lie on the posterior wall of the abdominal cavity, behind the parietal peritoneum.

• The kidney has a renal cortex, renal medulla, and renal pelvis.

• Kidneys excrete nitrogenous wastes including:

  • urea
  • uric acid
  • ammonia
  • creatinine

• The kidneys regulate blood volume by determining how much water is excreted and help regulate the blood's electrolyte content.

Further detail

• The renal artery is identified as the kidney's blood supply.

• The kidneys help regulate blood pH by controlling hydrogen-ion excretion and are involved in long-term blood-pressure regulation and red blood cell production through erythropoietin secretion.

📖 3. Nephron and Urine Formation

🔑 Key Concepts & Definitions

• Tubular reabsorption: The movement of water and dissolved substances from the glomerular filtrate in the tubules into the blood of the peritubular capillaries.
• Tubular secretion: The movement of very small amounts of selected substances from the blood into the tubules.

★ Must-know

• The nephron includes renal tubules and renal blood vessels.

• Urine formation involves:

  • glomerular filtration
  • tubular reabsorption
  • tubular secretion

Further detail

• Glomerular filtration produces glomerular filtrate, also called ultrafiltrate, and is associated with glomerular filtration pressure and the glomerular filtration rate (GFR).

💡 Memory Hook

Filtration → reabsorption → secretion

📖 4. Urine Composition and Disorders

🔑 Key Concepts & Definitions

• Urochrome: A pigment formed from the breakdown of hemoglobin in the liver.
• Oliguria: Urine output of less than 400 mL/day.
• Specific gravity: The ratio of the amount of solute to volume.
• Uremia: A condition in which substances that should have been excreted in urine remain in the blood.

★ Must-know

• Urine is composed mostly of water (95%), nitrogen-containing waste, and electrolytes.

Further detail

• Hormones that work on the kidneys include:

  • aldosterone
  • antidiuretic hormone
  • natriuretic peptides
  • parathyroid hormone
  • calcitonin

• Urinary nitrogenous waste includes:

  • urea
  • uric acid
  • ammonia
  • creatinine

📖 5. Ureters, Bladder, and Urethra

★ Must-know

• The urinary tract includes:

  • ureters
  • urinary bladder
  • urethra

• Urination is also called micturition or voiding.

Further detail

• The micturition reflex is identified as part of urinary function.

• Muscarinic agonists and medications with antimuscarinic side effects are identified as pharmacology issues related to the urinary system.