EXCRETION
BIOLOGY
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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
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
