Final answer:
The opisthonephric kidney is responsible for filtering blood and maintaining osmotic balance by regulating water and salt concentrations in the body. It contains nephrons with loops of Henle for urine concentration and renal pyramids for waste collection.
Step-by-step explanation:
The opisthonephric kidney is an organ found in certain vertebrates, including fish and amphibians, functioning in excretion and osmoregulation. Its main role is to maintain osmotic balance by filtering blood, reabsorbing essential electrolytes, and excreting metabolic wastes, such as urea.
This kidney type tends to be elongated with nephrons (functional units of the kidney) that have a mesonephric (middle segment) origin, and in some species may also have a metanephric (rear segment) component.
Despite the environment, an opisthonephric kidney can osmoregulate, meaning it works to control the concentration of water and salts within the body.
The nephrons typically consist of a renal corpuscle (comprised of a glomerulus and Bowman's capsule), followed by a renal tubule that contains the loop of Henle, which is essential for concentrating urine and conserving water. Wastes are collected in the renal pyramids, part of the kidney's medulla, which then empty into the ureter.