BRAINCAKEOsmoregulation in Mammals
In mammals the main organs of osmoregulation are the kidneys. They have two linked jobs:
• excretion: removing metabolic waste, mainly urea made in the liver, from the blood
• osmoregulation: controlling the water potential of the blood by adjusting how much water and how many ions are kept in the body
Each kidney contains about a million tiny tubules called nephrons. Blood is filtered at the start of each nephron, making a fluid called filtrate. Useful substances are then taken back into the blood, and the remaining fluid leaves as urine. By changing how much water is reabsorbed, the kidneys change the concentration of the urine:
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Key terms in this lesson
- water potential
- A measure of the tendency of water molecules to move out of a solution, which determines the direction of osmosis.
- loop of henle
- A hairpin-shaped section of a nephron that dips into the kidney medulla, creating a high solute concentration that allows concentrated urine to form.
More in Homeostasis
- Hormonal Control of the Heart
- Additional Responses
- Protein Homeostasis in the Liver
- Osmoregulation
- Structure and Function of the Kidney
- Ultrafiltration
- Selective Reabsorption
- Proximal Convoluted Tubule
All 41 lessons in Homeostasis · All Edexcel A-level Biology topics