c) Excretion is the process of getting rid of excess water only.
The human excretory system organs include:
- A pair of kidneys
- A pair of ureters
- A urinary bladder
- A urethra
Excretion is the process where all the metabolic wastes are removed from the body. Excretion in humans is carried through different body parts and internal organs in a series of processes.
- Blood contains both useful and harmful substances. Hence, we have kidneys which separate useful substances by reabsorption and toxic substances by producing urine.
- Kidney has a structural filtration unit called nephron where the blood is filtered. Each kidney contains a million nephrons.
- Capillaries of kidneys filter the blood and the essential substances like glucose, amino acids, salts, and the required amount of water get reabsorbed and the blood goes into circulation.
- Excess water and nitrogenous waste in humans are converted to urine.
- Urine thus produced is passed to the urinary bladder via the ureters.
- The urinary bladder is under the control of the Central Nervous System.
- The brain signals the urinary bladder to contract and through the urinary opening called the urethra, we excrete the urine.