What does the medulla of kidney contain?

The medulla of the kidney contains the collecting ducts, which are responsible for concentrating the urine. The collecting ducts are lined with specialised cells that can transport water and solutes out of the urine, allowing the kidney to produce a concentrated urine that is low in water content. The medulla also contains the loops of Henle, which are long, U-shaped structures that help to create a concentration gradient in the medulla. The loops of Henle are responsible for reabsorbing water and solutes from the urine, allowing the kidney to produce a concentrated urine.