excretion

• Excretion


  Removal of waste products of metabolism from the body
• Main metabolic waste products

  Carbon dioxide, bile pigments, urea
• Why is it important to remove metabolic waste products?

  Maintaining metabolism and homeostasis
• Details of excretion of bile pigments

  Formed from the breakdown of haemoglobin in the liver, excreted in the bile from the liver via the small intestine and gall bladder
• Details of excretion of nitrogenous waste products

  Formed from the breakdown of excess amino acids by the liver, all mammals produce urea to remove nitrogenous waste
• General structure of the liver

  Made up of lobes, has four vessels, has lobules
• Vessels in the liver

  Hepatic artery, hepatic vein, bile duct, hepatic portal vein
• Role of the hepatic artery

  To bring oxygenated blood to the liver from the heart via the aorta
• Role of the hepatic vein

  To carry deoxygenated blood from the liver to the heart by rejoining the vena cava
• Role of the hepatic portal vein

  To carry blood containing products of digestion from the intestines to the liver
• Name for liver cells

  Hepatocytes
• Structure of hepatocytes


  Large nuclei, prominent Golgi apparatuses, lots of mitochondria
• Structure of liver lobules

  Blood from the hepatic artery and vein mix in sinusoids, sinusoids surrounded by hepatocytes, sinusoids contain Kupffer cells, have canaliculi
• Reason for mixing blood in the sinusoids

  Increases the oxygen content of the blood from the hepatic portal vein
• Role of Kupffer cells

  To ingest foreign particles and help protect against disease
• Role of canaliculi


  To have bile secreted into them and carry it into the bile ductules which take it to the gall bladder
• Role of the bile duct

  To carry bile from the liver to the gall bladder so it can be stored until required to emulsify fats in the small intestine
• How the vessels are arranged in the lobules

  Hepatic artery and portal vein and bile duct are interlobular vessels on the outside, they lead either to or from the hepatic vein which is the interlobular vessel in the centre
• Role of the liver in storing glycogen

  Blood sugar concentration increases, insulin released, stimulates glycogen formation within the liver, can also be stimulated by glucagon to break down glycogen into glucose
• Detoxification reaction that happen in the liver

  Catalase breaks down hydrogen peroxide, ethanol dehydrogenase breaks down ethanol
• Equations showing the process of the breakdown of ethanol

  Ethanol -> Ethanal, Ethanal -> Ethanoate, Ethanoate + Coenzyme A -> Acetyl coenzyme A
• What is required for the break down of ethanol and fatty acids?

  NAD
• Types of reaction that the liver can do to detoxify

  Oxidation, reduction, methylation, combination
• Transamination


  Converting between amino acids
• Deamination


  Removing amine groups from a molecule
• Product of deamination


  Ammonia
• General process of the formation of urea

  Amino acid -> Ammonia -> Urea
• Name for the process of making urea

  Ornithine Cycle
• Equation for deamination


  Amino acid + Oxygen -> Ammonia + Keto acid
• Equation for the ornithine cycle

  Ammonia + CO2 -> Urea + H2O
• What can keto acids be used for?

  Respiration, lipid storage
• Sequence of events in the ornithine cycle

  Ammonia in, water out, citrulline, ammonia in, water out, arginine, water in, urea out, ornithine, carbon dioxide in
• Reasoning behind the process of nitrogenous compound removal

  Amino acids contain lots of energy so wasteful to excrete them
• Parts of the structure of the kidney

  Capsule. cortex, medulla, renal vein, renal artery, pelvis, ureter
• Capsule of the kidney


  Hard outer layer of the kidney, protects against mechanical damage
• Medulla of the kidney

  Beneath the cortex, contains the loop of Henle and the collecting duct
• Pelvis of the kidney

  Where urine is emptied into, made of connective tissue
• Parts of the nephron

  Afferent arteriole, efferent arteriole, glomerulus, Bowman's capsule, loop of Henle, proximal convuluted tubule, peritubular capillaries, distal convuluted tubule, collecting duct
• Which parts of the nephron are in the medulla?

  Loop of Henle, collecting duct
• How to identify a glomerulus down a microscope

  Circular, surrounded by clear space, high concentration of irregularly arranged nuclei,