Lecture Notes: Urinary System and pH Balance

Introduction

• Focus on the urinary system in human anatomy and physiology.
• Discuss maintaining osmotic pressure and eliminating metabolic waste.

Key Survival Challenges

1. Osmotic Pressure: Regulation of water and solute levels.
2. Eliminating Metabolic Waste: Includes carbon dioxide and nitrogenous waste.

Role of Various Organs

• Skin: Part of the integumentary system, excretes water.
• Liver: Detoxification, produces urea.
• Lungs: Expels carbon dioxide, part of the respiratory system.

Overview of the Urinary System

• Composed of kidneys, ureters, bladder, and urethra.
• Kidneys are key for urine production, containing approximately 1 million nephrons each.

Function of Nephrons

• Filtration: Occurs in the glomerulus within Bowman's capsule.
• Filtrate Composition: Water, glucose, amino acids, salts, ions, medications, vitamins, and urea.

Nephron Process

1. Reabsorption: Filtrate components move back into interstitial fluid.
2. Secretion: Waste remains in tubules; excretion via urine.

Types of Transport

• Passive Transport: Moves along concentration gradient.
• Active Transport: Requires ATP; moves substances against gradient.

Detailed Nephron Exploration

Proximal Convoluted Tubule

• Reabsorbs salt, water, glucose, amino acids, potassium, bicarbonate.
• Secretes hydrogen ions and ammonium.
• Regulates body's pH balance.

Loop of Henle

• Descending Limb: Water exits via aquaporins; solute concentration increases.
• Ascending Limb: Lacks aquaporins; salt exits via specific proteins.
  • Thin segment: Salt moves passively.
  • Thick segment: Active transport of salt.

Distal Convoluted Tubule

• Secretes hydrogen, potassium, ammonium.
• Reabsorbs salts, water, bicarbonate.
• Plays role in pH regulation.

Collecting Duct

• Converts filtrate to urine.
• Reabsorbs salt and water, controlled by hormones for body hydration.
• Urea partially reabsorbed, but some remains in filtrate.

Urine Production and Expulsion

• Urine produced in kidneys, moves through ureters, stored in bladder, excreted through urethra.

Conclusion

• Understanding the urinary system is crucial for maintaining body balance.
• Resources available for further learning and exam preparation.