_____ is a tuft of capillaries formed by the afferent arteriole which is a fine branch of _____

Answer

To answer the question, we need to fill in the blanks regarding the structure of the nephron and the blood supply involved.

1. **Identify the tuft of capillaries**: The term that fits in the first blank is "glomerulus." The glomerulus is a network of tiny blood vessels (capillaries) that plays a crucial role in the filtration of blood.

2. **Identify the source of the afferent arteriole**: The second blank refers to the source of the afferent arteriole. The afferent arteriole is a branch of the "renal artery." The renal artery supplies blood to the kidneys, and the afferent arteriole carries blood into the glomerulus.

Putting it all together, the complete answer is:
"**Glomerulus** is a tuft of capillaries formed by the afferent arteriole which is a fine branch of **renal artery**."