Urinary System and Nephrons Vocabulary

Water's Importance

• Essential for Bodily Reactions: Major component in cellular processes and breakdown of food molecules.
• Functions of Water:
  • Regulates body temperature.
  • Moistens tissues in the eyes, mouth, and nose.
  • Lubricates joints.
  • Dissolves minerals and nutrients for absorption.
  • Flushes out waste products.
  • Delivers nutrients and oxygen to cells.
• Water Loss: Occurs through urine, sweat, feces, and evaporation from lungs.

The Urinary System

• Purpose: Helps conserve water and maintains balance in the body.
• Consequences of Water Loss: Drops in blood pressure, shriveling of cells, loss of homeostasis.
• Components:
  • Kidneys: Filter blood to remove waste and produce urine.
  • Ureters: Carry urine from kidneys to the bladder.
  • Urinary Bladder: Stores urine.
  • Urethra: Conducts urine from bladder to the exterior.
• Homeostasis Functions: Regulates water, ions, pH, blood pressure, and red blood cells.

Structures of the Urinary System

• Kidneys:
  • Shape: Bean-shaped organs located along the abdominal cavity's posterior wall.
  • Function: Filtering of metabolic wastes, excess ions, and chemicals to form urine.
• Ureters: Tubes that transport urine from kidneys to the urinary bladder.
• Urinary Bladder: Sac-like organ for urine storage.
• Urethra: Length varies; ~2 inches in females, 8-10 inches in males.

Kidney and Nephron Diagram Labels

• Kidney Components:
  1. Cortex
  2. Medulla
  3. Pelvis
• Nephron Structures:
  1. Glomerulus
  2. Bowman's capsule
  3. Proximal convoluted tubule
  4. Loop of Henlé
  5. Distal convoluted tubule
  6. Collecting duct
• Additional Structures:
  • Branches of renal artery/vein.
  • Capillaries.
  • Calyx.

Functionality of Kidney Structures

• Renal Pelvis: Upper end of ureter, collects urine from kidney.
• Renal Medulla: Innermost kidney part; regulates urine concentration.
• Renal Cortex: Outer part housing arterioles/venules that perfuse nephrons.
• Medullary Pyramid: Transporting motor fibers in the brainstem (though not part of kidney function).
• Calyx: Collects urine from renal papillae.
• Renal Capsule: Membranous sheath protecting kidneys.

Components of the Nephron

• Afferent Arteriole: Feeds blood into glomerulus.
• Efferent Arteriole: Carries blood away from glomerulus.
• Glomerulus: Cluster of capillaries filtering waste from blood.
  • Filtration occurs here, initiating urine formation.
• Bowman's Capsule: Cup-like structure enclosing glomerulus; involved in blood filtration.
• Proximal Convoluted Tubule: Major site for reabsorption of Na+ and nutrients.
• Loop of Henle: Long loop regulating water and salt reabsorption.
• Distal Convoluted Tubule: Modulates extracellular fluid volume and electrolyte balance.
• Collecting Duct: Funnels urine from kidneys to ureter.

Filtration and Nephrons

• Functions:
  • Regulate body fluid balance and remove wastes.
  • Control blood pH, blood pressure, and blood volume.
• Nephrons: Tiny filters managing blood composition; around 1 million per kidney.
• Blood Pathway: Blood from renal artery → nephron → renal vein.
• Glomerular Filtration Rate (GFR): Approx. 125 ext{ mL/min}, indicating fluid and substance filtering rate.

Diagnosing Kidney Disease

• Kidney Function Issues: Failure to filter blood can lead to kidney disease.
• Polycystic Kidney Disease (PKD):
  • Caused by mutations in PKD-1 and PKD-2 genes.
  • Inheritance: Autosomal dominant; equal risk in males and females.
  • Mutations can be spontaneous without prior family history.
• Chronic Kidney Disease (CKD): Slow damage to kidneys; significant risk for many adults.
• eGFR Importance: Essential for assessing kidney function; lower values indicate severity and need for interventions like dialysis or transplantation.

Additional Information: Maintenance of Homeostasis

• Homeostatic Functions of Kidneys:
  • Ion Regulation: Control excretion of potassium, sodium, calcium, etc.
  • pH Control: Regulate hydrogen and bicarbonate ions for blood pH.
  • Osmolarity: Maintain isotonic conditions for cells via water control.
  • Coordinate water excretion through antidiuretic hormone (ADH).
  • Blood Pressure Monitoring: Adjusts reabsorption of water to manage blood volume.

Summary

• The urinary system plays a crucial role in maintaining homeostasis, regulating essential functions like fluid balance, waste removal, pH control, and blood pressure management through its complex structures and processes involving kidneys and nephrons.