Overview
This lecture covers the structure, function, and importance of the urinary (renal) system, including its roles in filtering blood, maintaining homeostasis, and handling waste elimination.
Structure of the Urinary System
- The urinary system (renal system) includes the kidneys, ureters, bladder, and urethra.
- Kidneys are bean-shaped organs located behind a layer of muscle in the lower back.
- Ureters transport urine from the kidneys to the bladder.
- The bladder stores urine until it is released through the urethra.
Function of the Kidneys
- Kidneys filter blood approximately 400 times per day to remove waste products.
- Blood enters the kidneys via the renal artery.
- Filtering occurs in about a million small units called nephrons.
- Clean blood leaves the kidneys through the renal vein and returns to the body.
Homeostasis and Regulation
- The urinary system helps maintain homeostasis by balancing water, ions (potassium, sodium, calcium, magnesium, phosphate), pH, and blood pressure.
- The kidneys remove excess ions and water to keep internal conditions stable.
Formation and Storage of Urine
- Waste and excess substances are removed from the blood to form urine.
- Urine contains urea (from protein breakdown), excess water, and some ions.
- The bladder can hold up to 800 milliliters of urine.
- Two sphincter muscles control urine release: the first is automatic, the second is under voluntary control.
Kidney Failure and Treatment
- Kidney failure can result from conditions like diabetes or high blood pressure.
- When kidneys fail, waste accumulates in the blood and dialysis may be required.
- Dialysis mimics kidney function by filtering blood and balancing ions.
- A kidney transplant may eventually be needed; only one kidney is necessary for normal function.
Key Terms & Definitions
- Renal system — another name for the urinary system.
- Nephron — the functional filtering unit of the kidney.
- Homeostasis — maintaining stable internal body conditions.
- Urea — waste from protein metabolism found in urine.
- Dialysis — a medical process that filters blood when kidneys fail.
- Sphincter — a muscle that controls the passage of urine from the bladder.
Action Items / Next Steps
- Watch the recommended video on how kidneys remove urine from the body.