excretion

• Excretion is the removal from organisms of:

  • toxic materials
  • waste products of metabolism
  • substances in excess requirements
• A metabolic waste of respiration is Carbon dioxide.
• Excretion takes place in:

  • urethra
  • skin
  • mouth
• Excretory organs:

  • kidneys
  • lungs
  • liver
  • skin
• The lungs are responsible for the excretion of gaseous wastes, primarily carbon dioxide from cellular respiration in cells throughout the body
• Exhaled air also contains water vapor and trace levelsof some other waste gases
• Deamination- break down of excess amino acid to form urea
• The liver:

  • Regulate blood sugar level
  • Stores substance such as iron and vitamins
• Sweat glands in the skin secrete a fluid waste called sweat or perspiration; however, its primary functions are temperature control and pheromone release.
• Sweating also maintains the level of salt in the body. It also removes traces of urea
• Selective reabsorption - process by which useful molecules(e.g. ions, glucose and amino acids), after being filtered out ofthe blood are reabsorbed or re-enters the bloodstream (fromthe filtrate formed in the nephron).
• nephrons - tiny structures that filter the blood
• Structures found in the cortex of nephrons:

  • Glomerilus
  • Boumans capsule
  • Proximal Convulated tubule
  • Distal convoluted tubule
  • Efferent arteriole
  • Afferent arteriole
• Structures found in the medulla of nephrons:

  • Loop of Henle
  • Collecting duct
• Excretion is important in living organisms because many waste products are harmful and if these build up in cells, they damage and kill the cells.
• The kidneys excrete water, nitrogenous waste and salts as urine
• The lungs excrete carbon dioxide and water vapour during exhalation
• The skin excretes water, urea and salts as sweat. It also excretes heat
• The liver excretes bile pigments and makes nitrogenous waste
• A renal artery carries blood to each kidney
• A renal vein carries blood away from the kidneys
• Waste substances produced during metabolism

  • Carbon dioxide - respiration
  • Water - respiration
  • Nitrogenous compounds - deamination
  • Bile pigments
  • Heat - metabolism
• Bile pigments are produced by the breakdown of haemoglobin from red blood cells in the liver
• Substances excreted from the body:

  • Carbon dioxide
  • urea
  • Bile pigments
• Nephrons produce urine
• Each nephron has a network of blood capillaries wrapped around it which leads from the glomerulus and joins into a venue into the renal vein
• Nephrons join into collecting ducts In the cortex
• Ultrafiltration occurs in the glomerulus
• Afferent arteriole gives the glomerulus blood at a high pressure
• kidneys - make urine
• ureter - tube carrying urine to the bladder
• bladder - bag with muscular walls which stores urine temporarily
• sphincter muscle - regulates urine release from the bladder
• urethra - takes urine from bladder to the outside of the body
• glomerulus - cluster of capillaries at the end of an arteriole
• selective reabsorption occurs in the nephrons
• ultrafiltration occurs in the glomeruli
• Proximal convoluted tubule reabsorbs the following:

  • glucose
  • amino acids
  • some water
  • some salts
  • hormones
  • vitamins
• Loop of hence reabsorbs the following:

  • some water
• Distal convoluted tubule reabsorbs the following:

  • some salts
  • some water