Overview
This lecture introduces the basic functions of the kidneys, focusing on nephron structure and the three main processes: filtration, reabsorption, and secretion.
Basic Kidney Structure and Function
- Kidneys contain many blood vessels that branch into the cortex.
- Each kidney has about 1 million nephrons, the functional units.
- The nephron consists of a renal corpuscle (filtering "ball") and a series of renal tubules (tubes).
- The main function of nephrons is to filter blood.
Kidney Filtration Process
- Blood enters the renal corpuscle where filtration begins.
- Filtration is based on size: large items (red/white blood cells, large proteins) remain in the blood.
- Small waste products (urea, uric acid), water, salts, and sugars leave the blood and enter the renal tubules.
Reabsorption of Useful Substances
- Filtration also allows important small molecules (sugar, salts, water) to leave the blood.
- Reabsorption is necessary to recover these useful substances back into the bloodstream.
- Capillaries near the tubules help transfer good substances back into the blood.
Secretion of Additional Wastes
- Not all waste is initially filtered out; some remains in the blood after the first filtration.
- During reabsorption, additional wastes are actively pumped from the blood into the renal tubules for excretion.
Key Terms & Definitions
- Nephron — The functional unit of the kidney that filters blood and forms urine.
- Renal Corpuscle — The ball-like structure in the nephron where filtration occurs.
- Renal Tubules — Tubes in the nephron where reabsorption and secretion happen.
- Filtration — The process by which small molecules move from the blood into the nephron.
- Reabsorption — The process of moving useful substances from the nephron back into the blood.
- Secretion — The active transport of additional waste from blood into the nephron for excretion.
Action Items / Next Steps
- Review and be able to explain the filtration, reabsorption, and secretion steps.
- Watch YouTube videos to reinforce understanding of kidney processes.
- Prepare for the next lecture on detailed nephron and renal tubule anatomy.