15.4 Excretion, Homeostasis And The Liver Flashcards
Excretion
Removal of waste products of metabolism from the body
Main metabolic waste products
Carbon dioxide
Bile pigments
Nitrogenous waste products (urea)
How is CO2 excreted?
Waste products of cellular respiration excreted from the lungs
What are bile pigments?
Breakdown of haemoglobin from old RBCs in the liver
How are bile pigments excreted?
Excreted in the bile from the liver into the small intestine via the gall bladder and bile duct
Why is urea formed?
From breakdown of amino acids in the liver
How is urea excreted?
By the kidneys in the urine
Blood vessel that supplies liver with oxygenated blood
Hepatic artery
Blood vessel that removes deoxygenated blood from the liver
Hepatic vein
Hepatic portal vein
Carries blood containing products from digestion from the intestines to the liver
Hepatocytes adaptations
Large nuclei
Prominent Golgi apparatus
Lots of mitochondria
Metabolically active cells
What happens in the sinusoids?
Blood from the hepatic artery and hepatic portal vein is mixed
This increases O2 content of blood supplied to hepatocytes
Kupffer cells
Act as macrophages for liver
Ingest foreign particles, help protect against disease
Journey of bile from liver
Hepatocytes secrete bile from RBC breakdown into canaliculi
Bile drains into bile ducts that take it to the gall bladder
Functions of liver
Carbohydrate metabolism
Deamination of excess amino acids
Detoxification
Carbohydrate metabolism
When blood glucose concentration rises, insulin rises and hepatocytes are stimulated to convert glucose into glycogen
When blood glucose concentration falls, hepatocytes convert glycogen back into glucose due to glucagon
Transamination
Conversion of one amino acid into another
Deamination
Removal of amine group from a molecule
Body cannot store amino acids or proteins, so excess would be excreted and wasted without hepatocytes
Deaminate amino acid - convert into ammonia - urea
How is ammonia converted into urea?
Via the ornithine cycle
How is hydrogen peroxide broken down?
Hepatocytes contain catalase enzyme
Splits hydrogen peroxide into oxygen and water
How is alcohol broken down?
Alcohol dehydrogenase
Ethanol is broken down into ethanal
Ethanol broken down into ethanoate - used in respiration, or to build fatty acids
Cirrhosis
Normal liver tissue is replaced by fibrous scar tissue
Stages of alcoholic liver disease
1- alcoholic fatty liver disease
2- alcoholic hepatitis
3- liver cirrhosis
Alcohol fatty liver disease
Big fat filled vesicles displace nuclei of hepatocytes and liver gets larger
Alcohol hepatitis
Fatty liver as well as damaged hepatocytes, sinusoids/hepatic veins become narrowed
Alcoholic cirrhosis
Liver tissue is irreversibly damaged
Hepatocytes die and replaced with fibrous tissue
Hepatocytes can no longer divide, so liver shrinks and loses ability to deal with toxins in the body
