15.4 Excretion, Homeostasis & the Liver Flashcards
What is excretion?
Removal of WASTE products
of METABOLISM from body
What are the main waste products in mammals?
CARBON DIOXIDE
BILE PIGMENTS
NITROGENOUS WASTE (UREA)
What are the blood vessels of the liver?
Hepatic artery
Hepatic vein
Hepatic portal vein
What are the main cells of the liver called?
hepatocytes
What are hepatocytes?
Main cells of the liver
Why do hepatocytes have large nuclei, prominent golgi apparatus and many mitochondria?
they are highly metabolically active
What are sinusoids?
spaces in liver lobule
brings oxygen + nutrient rich blood close to hepatocytes for diffusion.
What type of cells do sinusoids contain?
Kupffer cells
What are Kupffer cells?
macrophage-like cells found in sinusoids
which PHAGOCYTOSE foreign particles
protecting the liver from DISEASE
What are canaliculi?
channels in the liver lobule
which hepatocytes secrete bile into
What does bile contain?
bilirubin, a pigment from breakdown of haemoglobin
What is the bile duct?
vessel where bile drains into from the canaliculus
carries bile to gallbladder
What is a portal triad?
3 vessels found together in liver lobule
hepatic portal vein + hepatic artery + bile duct
In the liver, how is blood detoxified & removed of foreign particles, and how do hepatocytes receive nutrients?
- blood from HEPATIC PORTAL VEIN + HEPATIC ARTERY mix in SINUSOID
- Venous blood contains TOXIC BYPRODUCTS of metabolic processes, so DETOXIFIED (using catalase + alcohol dehydrogenase)
- Mixed blood contains high concentration of O2 + nutrients, diffuses into hepatocytes. - Foreign particles phagocytosed by KUPFFER CELLS
- lowers risk of disease - Blood drains into CENTRAL VEIN + transported to heart via HEPATIC VEIN
Which vessels does blood enter the liver lobule sinusoid by?
hepatic portal vein + hepatic artery
Which vessel does blood leave the liver lobule by?
central vein
How is bile formed, secreted + transported in the liver lobule?
- hepatocytes produce bile from BILIRUBIN
- SECRETED into CANALICULUS
- drains into BILE DUCT
- carried to GALLBLADDER for storage
What is bilirubin and what is it produced from?
yellow pigment
produced from breakdown of haemoglobin
What are the functions of the liver?
CARBOHYDRATE METABOLISM (glucoregulation)
DEAMINATION OF EXCESS AMINO ACIDS
DETOXIFICATION
What happens when blood glucose levels rise?
insulin levels rise (secreted by pancreas)
stimulates hepatoctes to convert glucose to glycogen
What happens when blood glucose levels decrease?
glucagon levels increase (secreted by islets of langerhans in pancreas)
stimulates hepatocytes to break down glycogen into glucose
What is deamination?
removal of amine group from an amino acid
Why are some amino acids in excess?
diet is unbalanced, never provides amino acids in perfect balance
Why must excess amino acids be either transaminated or deaminated?
body cannot store amino acids
What is transamination?
conversion of an amino acid type in excess
into an amino acid which is in short supply.
What is the process of the detoxification of ammonia called?
Ornithine cycle
What is the neutralisation of toxic products in the liver called?
detoxification
What substances are detoxified in the liver and using which enzyme?
hepatocytes contain catalase + alcohol hydrogenase:
catalase: H2O2 ⟶ H2O + H2
alcohol hydrogenase: ethanol ⟶ ethanal ⟶ ethanoate
Which enzymes are contained in hepatocytes?
catalase + alcohol dehydrogenase
What 2 processes can excess amino acid types undergo?
transamination
deamination
What is the ornithine cycle?
series of ENZYME CONTROLLED reactions
in the LIVER
converting AMMONIA from deamination ⟶ UREA
What are the steps of the ornithine cycle?
- amino acid deaminated ⟶ amine group ⟶ ammonia
- NH3 + CO2 + Ornithine ⟶ Citrulline + H2O
- Citrulline + NH3 ⟶ Arginine + H2O
- Arganine + 2H2O ⟶ Ornithine + Urea
What is the formula for urea?
CN2H4O
