Egestion: Egestion is the process by which the body eliminates digestive food residue and waste products from the body. These include indigestible matter, such as fiber, and dead cells and bacteria. These waste products are made into the form of feces in the large intestine and eliminated through the rectum and the anus.
Conditions that afflict egestion include diarrhea, obstruction, fecal impaction, constipation, gastroenteritis, ulcerative colitis, and colon cancer.
Excretion in Animals, Humans and Plants!
Chemical reactions occur in the cells of living organisms all the time to carry out the life processes.
The sum of these reactions is called metabolism. Metabolism produces useful products as well as toxic (poisonous) by-products.
These toxic substances have to be removed as they are harmful if allowed to accumulate. The removal of metabolic waste products from the body of an organism is known as excretion.
The major excretory products are carbon dioxide, excess water, and nitrogenous compounds like ammonia, urea, uric acid, etc. Carbon dioxide and water are produced in the process of tissue respiration. Nitrogenous compounds are formed from the breakdown of proteins and amino acids. Water and salts in excess of the body's needs are also excreted.
We acquire most of the water with our food and drink and some by metabolism, e.g., the water produced during cellular respiration. Other excretory products include chemicals from medicines, toxic substances, and circulating hormones that have already served their purpose. We will learn how metabolic wastes get eliminated.
Excretion in animals :
Many unicellular organisms like Amoeba throw out their wastes by diffusion from their body surface. Protozoan's have no organs for excretion. As they live in an aquatic habitat, their wastes are eliminated by diffusion through the plasma membrane.
Simple multicellular organisms like Hydra throw out solid waste matter through their mouth. Higher multicellular organisms have well-defined specialized excretory organs. These organs could be simple tubular structures as in flatworms and leech.
The excretory organs of insects (e.g., grasshopper, cockroach and housefly) are also tubular. They remove nitrogenous wastes from the body fluid and help in maintaining the water balance in the body.
In vertebrates, the main organs of excretion and maintenance of water balance are the kidneys.
Excretion in human beings :
Although the kidneys are the main organs of excretion, the skin, lungs and liver also help in excretion.
Skin:
Our skin has sweat glands, through which we excrete small amounts of water, urea and salts.
Liver:
The liver excretes bile, which contains bile pigments. These are produced by the breakdown of old RBCs in the liver. As hemoglobin breaks down, its iron is retained, while the pigment (haem) is excreted with the bile. The liver also excretes cholesterol.
Lungs:
The lungs help in getting rid of carbon dioxide, formed as a result of cellular respiration, through exhalation.
What is the difference between Egestion and Excretion?
• Excretion is simply the discharge of metabolic waste while egestion is the discharge of leftover food in the gut.
• The discharged matter has never passed through a cell in egestion, while it has in excretion.
• Egestion usually takes place at the anus and rarely through the mouth, whereas excretion takes place through many organs such as nares or mouth, skin, and cloaca or sex organs.
• Some excretory processes are mammal-specific but none of like that for egestion.
• Egestion is one process, but excretion could be different processes.
Reference:
www.differencebetween.com › Science & Nature › Science › Biology
www.biologydiscussion.com/essay/ excretion -in-animals...and.../1570
www.bbc.co.uk/schools/gcsebitesize/science/triple_ocr_gateway/.../1/