D4.1 - Overview of Excretory System

Excretory System Overview

• The excretory system is responsible for removing waste products from the body.
• Cellular respiration produces waste products that need elimination.
• Lungs eliminate carbon dioxide.
• Liver breaks down toxins.
• Kidneys eliminate toxins and maintain blood pH and water balance.
• The excretory system includes multiple systems working together to remove various wastes.

Principal Structures of the Excretory System

• The excretory system includes the kidneys, ureters, urinary bladder, and urethra.

Waste Excretion and Internal Equilibrium

• The process of cellular respiration produces wastes.
• These wastes must be eliminated.
• Lungs eliminate carbon dioxide.
• The liver breaks down ingested toxins.
• Kidneys help eliminate these toxins.
• Kidneys also maintain pH and water balance in the bloodstream.

Urinary Tract

• Kidneys remove toxins via the urinary tract.
• The urinary tract consists of the bladder, kidneys, ureters, and urethra.
• A human kidney is approximately the size of a fist.
• A human kidney weighs about 1 pound.

Importance of Kidneys

• Body cells break down complex compounds into smaller ones.
• Some simple compounds can be toxic.
• The liver removes amine groups from proteins, producing ammonia.
• The liver combines ammonia with CO2 to form urea.
• Kidneys filter out urea and uric acid from the blood.
• Urea and uric acid contain ammonia, which is unwanted.

Urinary Tract Terminology

• Renal arteries carry oxygenated blood to the kidneys.
• Kidneys remove waste and excess water.
• Kidneys maintain chemical balance, such as sodium, potassium and calcium.
• Ureters carry urine from the kidneys to the bladder.
• Urethra carries urine from the bladder to the body's exterior.
• Renal veins return blood from the kidneys to the heart.

Anatomy of the Urinary Tract

• The aorta carries oxygenated blood to the kidneys.
• The kidneys filter waste and excess water from the blood.
• Filtered substances are sent through ureters to the bladder.
• Urine exits the body via the urethra.
• Filtered blood returns to the heart through renal veins.

Kidney Terminology

• Cortex is the outer layer of the kidney.
• Medulla is the inner layer of the kidney, inside the cortex.
• Renal pelvis is the hollow area where the kidney joins the ureter.

Anatomy of the Kidneys

• Kidneys have three main layers:
  • Cortex: outer layer of connective tissue.
  • Medulla: inner layer beneath the cortex.
  • Renal pelvis: hollow chamber connecting the kidney to the ureter.

The Nephron

• Nephron is the functional unit of the kidney.
• Kidneys consist of millions of slender tubules called nephrons.
• Approximately one million nephrons are in each kidney.
• Nephrons filter blood, removing waste and returning needed substances.

The Nephron (Continued)

• Nephrons extend across the cortex and medulla.
• Nephrons remove waste products and other solutes from the blood.
• Nephrons allow for the reabsorption of water and solutes.
• Nephrons help maintain homeostasis.
• Waste and excess water not reabsorbed form urine.

Nephron Diagram

• Diagrams show nephrons, their parts, and their relationship with blood vessels.
• Structures within nephrons include Bowman's capsule, glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting duct.

Bladder Volume

• Bladder stretches when urine volume reaches 200 mL.
• Stretching sends a message to the brain, signaling the need to urinate.
• At 400 mL, a more urgent message is sent.
• At 600 mL, loss of voluntary control of bladder occurs.

Test your knowledge about the excretory system and its functions. This quiz covers the principal structures involved, waste excretion processes, and how the body maintains internal equilibrium. Perfect for students studying human biology or anatomy!