Which is the basic filtration unit in the human excretory system?

Hint: The organs that are involved in the removal of the waste products of metabolism from the animal body are termed as excretory organs. A pair of kidneys, a pair of ureters, a urinary bladder and a urethra are the various components of the human excretory system.

Complete answer:
The basic filtration unit in the human excretory system is a nephron. Nephrons or uriniferous tubules are the structure and functional units of the kidney. A kidney is composed of numerous nephrons that are held together by connective tissues. The nephrons are much coiled in the outer region of the kidneys and run almost straight in the inner region

There are two types of nephrons inside the kidneys, based on their location: cortical nephrons and Juxta-medullary nephrons.

- The cortical nephrons comprises about 80% of the total nephrons and lie in the renal cortex. They have very short loops of Henle that extend only upto a limit into the medulla.
- The juxta-medullary nephrons have their Bowman’s capsules, close to the junction of the cortex and medulla and have very long loops of Henle, extending deep into the medulla.
- The cortical nephrons help in controlling the normal water supply in the body. However, when there is shortness in the water supply, then juxtamedullary nephrons regulate the plasma volume.
- Each cortical nephron is formed of two parts- Bowman’s capsule and Renal tubule.
- Renal tubule is long and coiled and is formed of proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule

Hence, the correct answer is option (B).

Note: Excretion regulates the volume, composition, ionic contents, pH and osmotic pressure of the body fluids by removing substances in harmful quantity and conserving materials necessary for normal functioning of the body.