Homeostasis- Liver Flashcards
What is excretion?
The removal of metabolic waste from the body and the removal of by-products and unwanted substances from normal cellular processes
What substances are excreted from the body?
1) Carbon dioxide from cellular respiration
2) Urea from excess amino acids (nitrogenous waste)
3) Bile pigments from the breakdown of haemoglobin
How are amino acids stored in the body?
- Amino acids contain as much energy as carbohydrates
- However, body cannot store amino acids
- The body doesn’t want to waste such useful substances
- Therefore, liver deaminates excess amino acids and remaining molecules either used in respiration or converted to lipids for storage
Process of deamination:
1) Deamination
-Occurs in the liver
-Toxic amino group removed (ammonia)
Amino acid + Oxygen —-> Keto Acid + Ammonia
2) Formation of urea
-Ammonia reacted with carbon dioxide to form urea and water
-Urea is excreted
What is the liver?
- An accessory organ of the digestive system
- Reddish brown, wedge shaped organ with two lobes
- Heaviest internal organ and largest gland in human body
What are the functions of the liver?
1) Detoxification of various metabolites
2) Synthesis of proteins and biochemicals necessary for digestion and growth
3) Regulation of glucose store
4) Decomposition of red blood cells
5) Production of hormones
What is a hepatocyte?
Main type of cell making up liver tissue
What are the features of hepatocytes?
1) Have nuclei which are round and prominent, with dispersed chromatin
2) Have numerous mitochondria
3) Have prominent Golgi apparatus
4) Are very metabolically active
5) Have large amounts of smooth ER
6) Have many free ribosomes
What are Kupffer cells?
- Macrophages in the liver
- Primary function is to remove foreign debris, pathogens, gut bacteria and endotoxins from bacteria in the blood when it passes through the liver
Which blood vessels supply the Liver?
Liver receives a dual blood supply 1) Hepatic artery 2) Hepatic portal vein Away from Liver 1) Hepatic vein
What is the hepatic artery?
- Carries oxygenated blood directly from the heart via the aorta to the liver
- It is narrow and branched at the liver end only
What is the hepatic portal vein?
- Carries blood from the gastrointestinal tract, gallbladder, spleen and pancreas to the liver
- Contain nutrients and toxins extracted from digested food
- It is wide and branched at both the liver and small intestine ends
What is the hepatic vein?
- Drains deoxygenated blood from the liver into the inferior vena cava
- Only branched at the liver end
What is the biliary tract?
- System of ducts that collects products from the liver and the pancreas and drains them into the small intestine
- Bile consists of water, electrolytes, bile acids, cholesterol, phospholipids and bilirubin
- Some components of bile are synthesised by hepatocytes, others are extracted from the blood by the liver
Liver Anatomy:
- Liver composed of lobules and their associated blood vessels
- Each lobule is a six sided structure, consisting of hepatocytes
- Lobules arranged in irregular, branching, interconnected plates around a central vein
- Blood passes through large endothelium lined spaces called sinusoids
- Blood from hepatic artery and hepatic portal vein mixed together in sinusoids
