Which of the following describes a nephron?

The correct answer is a functional unit of the kidney because nephrons are the basic structural and functional units that make up the kidneys. Each kidney contains approximately one million nephrons, which are responsible for filtering blood, reabsorbing essential substances, and excreting waste products in the form of urine. The nephron consists of various components, including the glomerulus, tubules, and collecting ducts, each playing a crucial role in the process of urine formation.

This understanding of nephrons is fundamental in veterinary medicine, as they are vital in maintaining fluid and electrolyte balance, regulating blood pressure, and contributing to acid-base balance in the body. Recognizing the nephron's role can help in diagnosing and treating renal diseases in animals.