Overview
This lecture covers the structure and function of the nephron, the kidney's functional unit, focusing on its role in filtration, reabsorption, secretion, and urine formation.
Nephron Structure
- The nephron is the basic functional unit of the kidney, with 1-2 million per kidney.
- It begins with the renal corpuscle, made up of the glomerulus and Bowman's capsule.
- The proximal convoluted tubule follows, characterized by its convoluted (twisted) shape.
- Next is the loop of Henle, with descending and ascending limbs.
- The nephron continues into the distal convoluted tubule, also convoluted.
- The process ends in the collecting duct, which gathers urine from multiple nephrons.
Nephron Function
- Filtration occurs in the glomerulus, where blood is filtered to form filtrate.
- Bowman's capsule collects the filtrate from the glomerulus.
- Reabsorption retrieves valuable substances from the filtrate back into the blood, primarily in the proximal tubule, loop of Henle, distal tubule, and collecting duct.
- Secretion adds waste products from the blood into the tubule for elimination.
- The final urine, containing wastes, passes through the collecting duct to the renal pelvis, then moves via the ureter to the bladder, and exits through the urethra.
Key Terms & Definitions
- Nephron — The kidney’s functional unit responsible for filtration and urine formation.
- Renal corpuscle — Initial nephron section consisting of the glomerulus and Bowman's capsule.
- Glomerulus — Capillary network where blood filtration occurs.
- Bowman’s capsule — Structure collecting the filtrate from the glomerulus.
- Proximal convoluted tubule — First nephron tubule where most reabsorption and secretion occur.
- Loop of Henle — U-shaped nephron segment important for reabsorption.
- Distal convoluted tubule — Nephron segment further from the start, involved in reabsorption and secretion.
- Collecting duct — Channel that collects urine from several nephrons and leads to the renal pelvis.
- Filtration — Movement of substances from blood into the nephron.
- Reabsorption — Return of useful substances from the filtrate to blood.
- Secretion — Transfer of additional wastes from blood into nephron.
Action Items / Next Steps
- Review next lecture on glomerular filtration rate and factors affecting it.