The Excretory Sysyetm Removes Waste Products

What is excretion?

the removal of the wastes of metabolism from the body

What are the organs that are involved in the processing of wastes/in the excretion of wastes?

• lungs - involved in the excretion of CO2 that is produced by all body cells during cellular respiration

• liver - has an important role in processing many substances for excretion (e.g. amino acids)

• sweat glands - secret sweat, which is largely water, containing by-products of metabolism (e.g. salts, urea, lactic acid)

• alimentary canal - passes out bile pigments, which enter the small intestine with the bile and are the breakdown products of haemoglobin from RBC

• kidneys - responsible for maintains the constant concentration of materials in the body fluids, removing nitrogenous wastes of urea, uric acid and creatinine

What is the liver and its functions?

• located in the upper abdominal cavity

• very large organ with a host of different functions, including the preparation of materials for excretion

• proteins make up the structural materials of cells so as long as the body has a sufficient supply of carbohydrates and fats/stored fat, then little protein is used in energy-releasing reactions

  • excess protein from the diet cannot be stored in the cell, so processes are required to remove it from the body

• most of the protein breakdown occurring in the body at all times is incomplete

• worn-out cells are a source of protein, and are broken down into constituent amino acids, where most of it is used to make new proteins

  • very small amount of amino acids is lost from the body via urine, skin, hair and fingernails

• the proteins which have built up from aminos acids, become the primary constituents of cell structures, enzymes, antibodies and many glandular secretions but if other energy sources have been used up, the body is able to metabolize large amounts of proteins, breaking them down to produce energy

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