5.2: Homeostasis Flashcards
What is excretion?
The removal of metabolic waste from the body
What are the main excretory products?
- CO2 from respiration
- Nitrogen-containing compounds such as urea
- Bile pigments
What are the excretory organs?
- Lungs
- Liver
- Kidneys
- Skin
What is excreted out of the lungs and how?
- Carbon dioxide from respiring tissues —> bloodstream as hydrogencarbonate ions —> llungs
- CO2 diffuses into the alveoli to be excreted as you breathe out
What is excreted out of the liver and how?
- Some substances produced from metabolic roles will be passed into bile for excretion
- Involved in converting excess amino acids into urea (broken down by deammination)
- Nitrogen containing part of molecule is combined in CO2 to make urea
What is excreted out of the kidneys and how?
- Urea passed into the bloodstream to the kidney
- Transported in solutions: dissolved in plasma
- Removed from blood to be part of urine
What is excreted out of the skin and why?
- Sweat contains salts, urea, water, uric acid & ammonia
- Losing this maintains body temperature and water potential of the blood
Why is excretion important?
Some products are toxic and may interfere with cell processes, altering the pH
This means normal metabolism is prevented
Other products may act as inhibitors
What is deammination and why does it occur?
Amino acid + oxygen —> keto acid + ammonia
- The body cannot store excess amino acids
What is the formation of urea and why does it occur?
Ammonia + carbon dioxide —> urea + water
- Urea is less toxic than ammonia
What does the liver do?
Responsible for ensuring that everything in the blood is at the correct concentration (products of digestion, toxins and vitamins)
What is the hepatic artery?
- Oxygenated blood from the heart travels towards the liver
- Supplies the oxygen that is essential for aerobic respiration
What is the hepatic portal vein?
Deoxygenated blood enters the liver from the digestive system
What is the deoxygenated blood like in the hepatic portal vein?
- Blood is rich in the products of digestion
- Concentration are uncontrolled
- Important that substances do not continue to circulate around the body before their concentrations are adjusted
What is the structure of the liver?
- Liver is divided into lobes
- Lobes are further divided into lobules
- Cells, blood vessels and chambers are arranged to ensure the greatest possible contact between the blood and the liver cell