How do the kidneys clean the blood? (1 point)

• Kidneys clean the blood by breaking down nutrients.
• Kidneys clean the blood by filtering it to remove wastes.
• Kidneys clean the blood by absorbing nutrients.
• Kidneys clean the blood by destroying microbes and preventing infection.

4.6.7 - Quick Check: The Excretory System

Biology B - Winn / 4. The Human Body / 4.6. The Excretory System
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Kidneys clean the blood by filtering it to remove wastes.

The correct answer is: Kidneys clean the blood by filtering it to remove wastes.

To understand how the kidneys clean the blood, we need to know a bit about the anatomy of the kidneys. The kidneys are two bean-shaped organs located on either side of the spine in the lower back. Each kidney contains millions of tiny filtering units called nephrons.

The process of cleaning the blood starts in the nephrons. As blood passes through the nephrons, there are small blood vessels called capillaries that weave around the nephrons. When blood enters these capillaries, there is a process called filtration that occurs.

During filtration, the blood pressure forces small molecules like water, electrolytes, and waste products to pass from the capillaries into tiny tubules in the nephron. These waste products include urea, uric acid, creatinine, and various toxins. Meanwhile, larger molecules like proteins and blood cells are too big to pass through the filtration process and remain in the blood.

Once the waste products are in the tubules, the kidneys selectively reabsorb certain substances that the body needs, such as water, glucose, and electrolytes. By reabsorbing these substances, the kidneys prevent excessive loss and help maintain homeostasis in the body.

After the filtration and reabsorption processes, the remaining waste products, along with excess water and electrolytes, flow through the tubules and eventually form urine. This urine travels from the kidneys down to the bladder through tubes called ureters, and is eventually eliminated from the body through the urethra.

So, to summarize, the kidneys clean the blood by filtering it in the nephrons, removing waste products and excess water, while reabsorbing essential substances.

http://kidshealth.org/kid/htbw/kidneys.html