Excretion and the urinary system
Introduced| English | Meaning |
|---|---|
| excretion/ekˈskreʃn/ | The removal from an organism of metabolic waste and substances present in excess of its requirements. |
| kidneys/ˈkɪdniz/ | The pair of organs that filter blood and produce urine. |
| urea/juːˈrɪə/ | A nitrogen-containing compound formed from excess amino groups in mammals and excreted mainly in urine. |
| urine/ˈjʊərɪn/ | The fluid waste produced by the kidneys, containing urea, excess salts and water. |
| ureters/ˈjʊəretəz/ | The tubes carrying urine from the kidneys to the bladder. |
| bladder/ˈblædə/ | The muscular sac storing urine. |
| urethra/jʊəˈriːθrə/ | The tube carrying urine out of the body. |
| deamination/ˌdiːmɪˈneɪʃn/ | The removal of an amino group from an amino acid or another molecule. |
Taking out the chemical rubbish
- Your body's reactions constantly make waste that would poison you if it built up.
- Removing this waste is excretion 排泄, and the kidneys 肾脏 are the body's main filter.
Urea is produced from the breakdown of excess:
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The liver makes urea from excess amino acids.
Carbon dioxide is excreted by the:
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CO₂ from respiration leaves via the lungs.
What needs removing
- Carbon dioxide (from respiration) — removed by the lungs.
- Urea 尿素 (from breaking down excess protein) — removed by the kidneys.
- Excess water and salts — also removed by the kidneys.
The kidneys make urine 尿液, which passes down the ureters 输尿管 to the bladder 膀胱 and out of the urethra 尿道
Excretion and the kidneys
The kidneys clean the blood, removing urea and adjusting water, and make urine.
The organs that filter the blood to make urine are the:
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Kidneys filter blood and form urine.
Put the urinary pathway in order.
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Kidney → ureter → bladder → urethra.
The urinary system
- The kidneys filter the blood, making urine.
- Urine flows down the ureters to the bladder, where it is stored, then out through the urethra.
A dialysis machine cleans the blood when the kidneys stop working
The breakdown of excess amino acids in the liver is called ______.
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Deamination produces urea.
The liver's role
- The liver breaks down excess amino acids, making urea (this is deamination 脱氨基作用).
- The urea is carried in the blood to the kidneys to be removed.
Excretion removes waste from reactions, not undigested food. Urea and carbon dioxide are made by the body's own chemistry. Faeces (undigested food) leave by egestion, which is not excretion.
The kidneys filter the blood and make urine
You've got it
- excretion removes metabolic waste: CO₂ (lungs), urea and excess water/salts (kidneys)
- urinary system: kidneys → ureters → bladder → urethra
- the liver makes urea from excess amino acids (deamination)