9.2 Urine Formation in the Nephron

• What are the four processes of the formation of urine?

  1. Glomerular filtration
  2. Tubular reabsorption
  3. Tubular secretion
  4. Water reabsorption
• How does glomerular filtration work?

  Moves water and solutes (except proteins from blood plasma into the nephron)
• How does tubular reabsorption work?

  Removes useful substances like Na+ from the filtrate and returns them into the blood for reuse by body systems
• How does tubular secretion work?

  Moves additional wastes and excess substances from the blood into the filtrate
• How does water reabsorption work?

  Removes water from the filtrate and returns it to the blood for reuse by body systems
• What's the first process of the formation of urine?

  Glomerular filtration
• What are the two factors that contribute to the glomerular filtration?

  1. Permeability of the capillaries of the glomerulus
  2. Blood pressure
• What does the tubular reabsorption process involve in the proximal tubule?

  Active and passive transport mechanisms and the cells are richly endowed with mitochondria
• What is the function of the loop of Henle?

  Reabsorb water and ions from the glomerular filtrate
• What does the descending limb of the loop of Henle encounter?

  An increasingly salty environment and the cells are permeable to water and slightly permeable to ions
• What happens when the cells are permeable to water and slightly permeable to ions in the descending limb?

  The medulla's salty environment and permeability of the descending limb results into water diffusing from the filtrate to the capillaries by osmosis.