Urinary System Overview

Overview of the Urinary System

• Function: Primarily responsible for urine production and water conservation.
• Roles: Critical for determining what stays in the body and what is excreted.

Components of the Urinary System

• Two Main Groups:
  1. Kidneys: Major excretory organs.
  • Function: Filter blood and produce urine.
  1. Urinary Tract: Includes three components that transport urine out of the kidneys:
  • Ureters: Tubes that carry urine from the kidneys to the urinary bladder.
  • Urinary Bladder: Temporary storage for urine before expulsion.
  • Urethra: Controls the expulsion of urine from the bladder to outside the body.

Functions of the Kidneys

• Homeostasis: The kidneys play a critical role in maintaining bodily balance through various mechanisms:
  • Fluid Balance: Regulates water volume in the body, determining how much water to retain or expel.
  • Electrolyte Balance: Maintains levels of essential electrolytes by regulating their loss or retention.
  • Acid-Base Balance: Provides long-term regulation of blood pH, contrasting with the instant effects of the respiratory system.
  • Metabolic Waste Removal: Eliminates metabolic byproducts.
  • Blood Pressure Maintenance:
  • Involves fluid balance regulation and the hormonal influence of angiotensin II on blood volume and peripheral resistance.
  • Regulation of Erythropoiesis:
  • Produces the hormone erythropoietin, which stimulates red blood cell production.
  • Activation of Vitamin D: Necessary for calcium homeostasis.
  • Gluconeogenesis: Produces glucose from non-carbohydrate sources during fasting.

Filtrate vs. Urine

• Filtrate:
  • Initial fluid produced in the kidneys through blood filtration.
  • Consists of blood plasma components excluding proteins (e.g., water, ions, nutrients).
• Urine:
  • Heavily modified filtrate after processing within the kidneys.
  • Primarily composed of water, electrolytes, and metabolic waste.
  • Represents less than 1% of the filtrate produced (99% reclaimed by the body), indicating how vital the reabsorption process is to life.