Absorbed Nutrients

• Assimilation


  • the process whereby some of the absorbed nutrients are converted into new cytoplasm used to provide energy
  • after absorption, the blood in the villi is rich in nutrients. The blood capillaries unite to form larger blood vessels, which then unite to form the hepatic portal vein
  • the hepatic portal vein transports nutrients from the small intestine to the liver
• Glucose after absorption


  • in the liver, most absorbed sugars are converted into glycogen and stored
  • some glucose is transported by blood leaving the liver, and is distributed around the body to be used for energy during cell respiration
  • excess glucose is transported back to the liver and stored as glycogen for use in the future
• Amino acids after absorption


  • amino acids that enter the cells are converted into new cytoplasm that is used for growth and repair of worn-out parts of the body
  • amino acids are also used to form enzymes and hormones
  • in the liver, excess amino acids have their amino groups removed and converted into urea (deamination)
  • urea is removed from the body in the urine, remains of deaminated amino acids are converted into glucose in the liver
• Fats after absorption


  • Fats are absorbed into the lymphatic capillaries, which join to form larger lymphatic vessels, discharging fats in to blood stream
  • blood carries fats to all parts of the body, especially the liver
  • when there is enough glucose, fats are not broken down to provide energy needed for vital activities in the body
  • Excess fat is stored in adipose tissues beneath the skin and around the heart and kidneys. Adipose tissues protect organs by acting as shock absorbers
• Functions of liver


  1. production of bile
  2. deamination of amino acids
  3. regulating blood glucose concentration
  4. breakdown of hormones
  5. detoxification
• Regulation of blood glucose concentration


  • liver plays key role in keeping amount of glucose in the blood constant, especially after a heavy meal or fasting
  • pancreas contains special groups of cells known as islets of Langerhans which secrete the hormones insulin and glucagon into the bloodstream. Both insulin and glucagon together help to regulate the level of glucose in the blood
• Breakdown of hormones


  Hormones are broken down in the liver after they have served their purpose
• Detoxification


  • harmful substances may be absorbed into the blood from the gut, these substances (e.g. food preservative benzoic acid) are made harmless by the liver cells
  • alcohol is broken down by the liver. Alcohol can cause damage to the digestive system and slow down brain functions
  • liver cells contain an enzyme which breaks down alcohol to compounds that can be used in respiration, providing energy for cell activities
• Hepatic vein vs hepatic portal vein

  • Hepatic vein has oxygen-poor blood
  • Hepatic portal vein has nutrient-rich blood
• Hormones


  • a chemical substance produced in very small quantities by an endocrine gland. it is transported in the bloodstream to target organs where it exerts its effects
  • can influence growth, development and activity of an organism
  • chemical messengers that help various parts of the body to respond, develop and work together smoothly
  • some glands produce only hormones, while other glands such as the pancreas produce both hormones and other secretions
• Pancreas


  • produces pancreatic juice
  • contains special groups of cells known as Islets of Langerhans which secrete hormones insulin and glucagon into the bloodstream
  • hormones help to regulate concentration of glucose in the blood
• High blood glucose level


  • After a meal, blood glucose level increases above normal, pancreas detects this and produces insulin
  • insulin is transported in the blood to liver and muscle cells
  • insulin makes cell membranes more permeable to glucose, allowing more glucose to diffuse into the liver and muscles cells
  • insulin stimulates liver and muscle cells to convert excess glucose into glycogen
  • Insulin increases the use of glucose for respiration
• Low blood glucose level


  • when blood glucose level drops, pancreas detects the change and produces glucagon
  • glucagon is transported in the blood to the liver
  • glucagon increases blood glucose concentration by stimulating the conversion if glycogen into glucose