Q.Select the correct match:

Think of how a city handles waste water. It needs treatment plants to clean it, pipes to carry it, a holding tank to store it, and a final outlet to release it. The human body organises its excretory plumbing in much the same orderly way, and together these parts make up the excretory system structures.

In humans, the excretory system is built from a small set of organs working as a team: a pair of kidneys, a pair of ureters, a single urinary bladder and a urethra. Each has a clear role. The kidneys are the central organs, the treatment plants where urine is actually made. They are reddish-brown, bean-shaped structures lying against the back inner wall of the abdominal cavity. The ureters are the pipes that carry urine down from each kidney. The urinary bladder is the storage tank that collects and holds the urine, and the urethra is the final channel through which urine leaves the body.

Inside a kidney lies a further layer of structure. Each one is wrapped in a tough capsule and organised into an outer cortex and an inner medulla, with the medulla broken into cone-shaped medullary pyramids. On the inner concave surface is a notch called the hilum, the gateway through which the ureter leaves and blood vessels and nerves enter. Just inside sits a funnel-shaped renal pelvis with finger-like extensions called calyces. Most importantly, each kidney holds close to a million tiny tubular units called nephrons, and the nephron is the true functional unit where urine is made.