MCAT Basics (from MedSchoolCoach) The Excretory System
Apr 17, 2025
Explore the fascinating roles of the kidneys, liver, skin, lungs, and large intestine in waste elimination. Discover how kidneys filter blood and how the liver's lobules manage metabolic breakdown. Learn about the importance of alveoli in gas exchange and the body's urea cycle. Uncover the processes of ammonia conversion and electrolyte regulation. Dive into how the liver detoxifies substances and how carbon dioxide is exhaled to avoid acidosis. Each organ plays a vital part in maintaining our body's balance and health.
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Excretory System Defined And Distinguished
- The excretory system removes metabolic wastes, excess electrolytes, toxins, and gases to maintain homeostasis.
- It differs from the digestive system (inputs) and contains the urinary system (urine production and elimination).
Kidney Structure And Urine Pathway
- Kidneys contain about a million nephrons that filter toxins, salts, and water from blood and produce urine.
- Urine travels via long ureters to the bladder, which stores urine before expulsion through the urethra.
Hepatic Lobule Flow Patterns
- The liver has two lobes and hexagonal hepatic lobules with portal triads at the corners and a central vein in the middle.
- Blood flows from the triads through sinusoids into the central vein while bile flows from the lobule center outward toward bile ducts.
