The process of removal of biological wastes which are toxic to our body is known as excretion. Biological wastes such as nitrogenous compounds, undigested food matter are removed through specialized organs of the excretory system in humans.
Excretory system of humans:
The excretory system of humans consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. The urine produced in kidneys is passed through the ureters and collected in the urinary bladder for excretion.
Urine is produced so as to filter out the waste products such as urea and uric acid from the blood. The blood from different organs of the body is collected and drained into various blood capillaries present on the outer wall of kidneys. Each blood capillaries on the kidneys have a cup-shaped tube to collect the capillaries.
The kidneys play an essential role infiltration and the structural and functional unit of filtration is called as nephrons. Each kidney is made up of several nephrons that are packed together. The simpler food substances such as glucose, amino acids, ions, and salts are selectively reabsorbed from the urine by the nephrons in the kidneys. If the water is present excessively, there is increased absorption of the ions from the urine.
The urine thus formed in the kidney is passed on to the ureters and is collected in the urinary bladder. The urinary bladder is a thick-walled muscular bag which collects the urine until a certain amount of pressure acted by nervous system is provided. Once the pressure builds up, the urine is excreted out of the body.
Excretion in plants:
Plants have different methods to excrete the biological wastes. The most common method of excretion is a loss of water through a process called as transpiration. Plants have the ability to lose old tissues and leaves that collect dead cells over a period of time. Other ways of excretion include storing of waste products in cellular vacuoles, in old xylem in the form of gums and resins and dissipating wastes into the soil around the plants.