The fluid that enters vertebrate nephrons is called the filtrate. What is the source of the filtrate?

• A. Urine
• B. Lymphatic fluid
• C. Cells of the kidney
• D. The loop of Henle
• E. Blood in capillaries

Answer: (E)

Verified step by step guidance

1. Understand that the nephron is the functional unit of the kidney, responsible for filtering blood and forming urine.
2. Recognize that the process of filtration occurs in the glomerulus, a network of capillaries located at the beginning of the nephron.
3. Identify that the filtrate is the fluid that is filtered out of the blood in the glomerulus and enters the nephron.
4. Note that the filtrate contains water, ions, glucose, and small molecules, but not large proteins or blood cells, which remain in the blood.
5. Conclude that the source of the filtrate is the blood in the capillaries of the glomerulus, as it is from here that the fluid is filtered into the nephron.