A juxtamedullary nephron features long loops of Henle that extend far into a kidney's medulla, whereas cortical nephrons have short loops of Henle and are almost entirely embedded in the kidney's cortex, according to Dr. Dawn A. Tamarkin of Springfield Technical Community College. These loops of Henle in nephrons are responsible for extracting minerals and reabsorbing water into the body.
Long loops in juxtamedullary nephrons create a gradient in the kidneys by which the osmosis of solutes occurs. This is where substances are filtered out of the blood and into the urine. As water dips down into the loop of Henle in these nephrons, water is permeable to the surrounding tissue. As the countercurrent goes back upward, salt is permeable to the surrounding medulla, according to Midlands Technical College.
Both types of nephrons regulate solutes and water in the blood. Southwest Tennessee Community College states that of the total amount of nephrons in the kidneys, 15 percent are juxtamedullary nephrons and 85 percent are of the cortical variety.
The medulla is the inner part of the kidney in mammals. The cortex is the outer layer that surrounds the medullas. Loops of Henle are small tubes that allow for water and minerals to pass into urine or back into the body, according to Encyclopedia Britannica.