Excretion in Humans and Plants

It is the biological process by which toxic metabolic wastes are removed from the body.

• Many unicellular organisms eliminate wastes from their bodies by simply diffusing them into the surrounding water
• The same job is performed by specialised organs in complex multicellular organisms

Excretion in Humans

Skin

Skin acts as a minor excretory organ in humans. The waste product excreted by the skin is sweat. Sweat is produced by the sweat glands. It is composed of salts and urea. When the sweat comes out from the human body it helps in keeping the body cool in hot climates.

Lungs

Lungs help in removing excess carbon dioxide and some water vapour from our bodies that occurs when we breathe out.

Human Excretory System

The human excretory system is responsible for the elimination of waste in human beings. Humans have two kidneys, two ureters, a urinary bladder and a urethra as part of their excretory system.

Kidneys

• Kidneys are the major excretory organ that removes waste from the human body
• Kidneys are bean-shaped and are located on either side of the backbone
• The length of a kidney varies from 10 to 12 cm and weighs about 120g to 170g in human beings
• Our kidney has a number of subunits known as nephrons
• Nephrons are referred to as the functional unit of kidneys
• One human kidney can have 1 million nephrons
• Nephrons carry out the process of secretion and the process of excretion
• Nephrons are made up of a malpighian body that has two parts- glomerulus and renal tubules
• The product of the kidney is urine

Ureter

• The kidney is connected to the renal pelvis by a thin and muscular tube which is known as the ureter
• The ureter functions between the kidneys and the urinary bladder

 Urinary Bladder 

• It is a muscular sac-like structure that stores urine
• It is responsible for controlling the passage of urine
• It has the capacity to store urine of about 400 to 600 ml

Urethra

• It helps to expel urine from the body
• It is also responsible for carrying sperm in males

Mechanism of excretion

• One on each side of the backbone, the kidneys are positioned in the belly
• Urine is transported from the kidneys to the urinary bladder, where it is retained until it is expelled through the urethra the ureters

• The kidneys eliminate nitrogenous waste from the blood, such as urea or uric acid

• The fundamental filtration unit in the kidneys is a cluster of blood capillaries with very thin walls

• The filtration units known as nephrons are found in enormous numbers in each kidney
• The cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate is related to each capillary cluster in the kidney
• Each kidney’s urine eventually reaches the ureter, a lengthy tube that connects the kidneys to the urinary bladder

• Urine is stored in the urinary bladder until it is pushed out via the urethra by the pressure of the inflated bladder
• The bladder is a muscular organ that is controlled by the neurological system

Artificial kidney (Haemodialysis)

• An artificial kidney can be utilised in the event of renal failure
• Artificial kidneys are made up of multiple semi-permeable tubes suspended in a tank of dialysing fluid
• Except for the absence of nitrogenous wastes, this fluid has the same osmotic pressure as blood
• An artificial kidney is a device that uses dialysis to eliminate nitrogenous waste products from the blood

Excretion in Plants

To get rid of the trash, plants employ a variety of methods. Waste material could be kept in cell vacuoles or as gum and resin, removed in falling leaves, or expelled into the surrounding soil, for example. Plants can also excrete water by transpiration.

Conclusion

Excretion is the biological process by which toxic metabolic wastes are removed from the body. In unicellular organisms, the waste is eliminated from the body by simple diffusion but in complex multicellular organisms, it is done by specialised organs. Excretion in humans can be done with the help of skin, Lungs and Kidneys. Kidneys are the main organs for excretion that removes the waste from the human body. They are bean-shaped and are located on the other side of the backbone. Kidneys contain a number of subunits known as nephrons which are referred to as the functional unit of the kidney. One human kidney can have 1 million nephrons. Nephrons carry out the process of secretion and the process of excretion. Nephrons are made up of a malpighian body that has two parts- glomerulus and renal tubules. The product of the kidney is urine. The excretory system in humans also comprises the ureter, urinary bladder and urethra. The ureter functions between the Kidneys and the urinary bladder. The urinary bladder is responsible for controlling the passage of urine and it stores the urine. The urethra is responsible for expelling urine out of the body.  An artificial kidney can be utilised in the event of renal failure. It is a device that uses dialysis to eliminate nitrogenous waste products from the blood. Plants can also excrete waste in the form of water vapour by the process of transpiration.

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