Ch 16Excretory Products and their Elimination — Class 11 Biology, concept-first.

Before looking at the human system in detail, it helps to see the bigger picture: what exactly needs to leave the body, and how different animals across the animal kingdom manage it.

In humans, the excretory system is built around a small set of organs that together produce, carry, store and expel urine: a pair of kidneys, a pair of ureters, a single urinary bladder and a urethra.

Urine is not made in a single step. It is produced through three linked processes that occur in different regions of the nephron: glomerular filtration, reabsorption and secretion.

Each segment of the renal tubule has its own particular job in shaping the filtrate into urine, handling reabsorption and secretion in characteristic ways.

One of the defining abilities of mammals is that they can produce a urine much more concentrated than their body fluids.

Kidney function is not left to run on its own — it is closely monitored and adjusted by hormonal feedback loops.

Micturition is the act of passing urine out of the body. It is not continuous: urine produced by the nephrons is first carried down to the urinary bladder, where it collects and is held until the body…

The kidneys are the main organs of excretion, but they are not the only ones. The lungs, the liver and the skin also share the task of clearing waste substances from the body.

When the kidneys fail to work properly, waste that they would normally clear begins to build up in the body, and this can become dangerous.

The body constantly produces substances it must get rid of, including many nitrogen-containing compounds, ions, carbon dioxide and water.

Higher-order thinking problems from the NCERT Exemplar.