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  7. A2 Unit F214 - Communication, Homeostasis and Energy

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excretion topic summary
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a brief summary of excretion : excretory organs, liver and kidney structure, kidney transplant, kidney failure, pregnancy testing, anabolic steroid testing. diagrams for structure of liver and kidney bullet points to summarise sequence of events in excretion key words highlighted for better r...

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  • January 4, 2024
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  • 2023/2024
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EXCRETION
BIOLOGY
___


Notes

Removal of metabolic waste

Kidneys, liver + lungs remove toxic products of metabolism from blood

- Kidneys control water potential of blood + excrete waste in urine
- Liver excretes waste products via bile into small intestine, then it’s removed in
faeces, and metabolises ingested toxins
- Lungs excrete CO2

2 main excretory products :

1. CO2: product of aerobic respiration

Build-up: reduce oxygen transport by blood by causing oxyhaemoglobin to
dissociate with oxygen & combining with haemoglobin to form
carbaminohaemoglobin

= respiratory acidosis: blood pH falls below 7.35 = homeostatic mechanisms
removing CO2 don’t function properly

2. Excess amino acids undergo deamination, removing their amine group

Amino acid + oxygen → keto acid + ammonia

Keto acid used in respiration / stored as carbohydrate or fat

Ammonia water soluble and toxic = converted to urea in Ornithine cycle

, 3. Bile pigments from breakdown of haemoglobin from old red blood cells in liver,
excreted in bile into small intestine via gall bladder + bile duct


LIVER
● Hepatic artery : oxygenated blood from aorta
● Hepatic vein : carries blood away from liver to vena cava
● Hepatic portal vein : blood rich in nutrients from small intestine

Cylindrical lobule: rows of hepatocytes (liver cells can divide + replicate) with :

- Mitochondria : produce lot of ATP =active
- Golgi apparatus: making , modifying + packaging lots of proteins
● Centre: central vein (branch of hepatic vein)
● Blood from hep artery + hep portal vein flows btw rows of hepatocytes towards
central vein in sinusoids (channels) that increase oxygen content of blood from
hep portal vein
● Hepatocytes take up what required from blood = shed their products into it
● Btw rows canaliculi (channels) receive bile secreted from hepatocytes + connect
up with bile ducts at edge of lobule
● Bile emulsifies lipids, stored temporarily in gall bladder b4 periodic release into
small intestine
● Kupffer cells (macrophages) attached to walls of sinusoids that destroy old
erythrocytes + remove bacteria & foreign particles from blood

, Stained with haemotoxylin + eosin


FUNCTIONS

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