Role of the Kidneys and Water Regulation

Functions of the Kidneys

• Filtering Blood: The primary function is to filter the blood and remove waste products.
• Waste Product - Urea:
  • Formed in the liver during deamination.
  • Deamination converts excess amino acids into fats and carbohydrates for storage.
• Regulation of Ions and Water:
  • Ions like sodium and potassium are essential, but need to be regulated to prevent cellular damage.
  • Ions are lost during sweating and primarily regulated through the kidneys.

Water Regulation

• Sources of Water:
  • Consumed through food and drinks.
  • Lost through skin (sweat), lungs (breathing), and mainly kidneys (urine).
• Importance of Regulation:
  • Osmosis affects cells depending on body water levels.
  • Excess water can cause cells to swell and burst.
  • Lack of water can cause cells to shrink.

Nephron Structure and Function

• Each kidney contains around one million nephrons.
• Filtration Process:
  • Nephrons filter blood, absorbing small substances like water, glucose, amino acids, and urea.
  • Large molecules like proteins and cells are not filtered.
• Selective Reabsorption:
  • Glucose is fully reabsorbed as it is always useful.
  • Water is partially reabsorbed.
  • Urea is not reabsorbed, forming part of urine.

Regulation of Water Levels

• Hypothalamus and Water Concentration:
  • Detects water concentration in the bloodstream.
  • Signals the pituitary gland if water levels are low.
• Antidiuretic Hormone (ADH):
  • Released by the pituitary gland upon receiving signals from the hypothalamus.
  • ADH instructs kidney tubules to reabsorb more water, reducing urine production.
• Negative Feedback Loop:
  • Maintains water balance by adjusting ADH levels in response to body water levels.
  • Decreases ADH if water levels are high, increasing urine production.