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7-human nutrition - Coggle Diagram

- - - - they are needed for energy
      - they are needed to make cell membranes
      - if in excess, it is stored under the skin or around some organs
    - - they are organic substances needed only in small amounts
        
        if you do not get enough of them you may get a deficiency disease
    - - they are inorganic substances needed only in small amounts
    - - they are needed to build new cells
      - they are used to make new proteins, including antibodies
    - - it is present in cytoplasm, blood plasma and as a solvent for metabolic reaction
    - - they are needed for energy
      - they include starch and sugar
    - - fibre helps to stimulate peristalsis (the movement of muscles in the alimentary canal)
- - - - food does not pass through them
      - the pancreas secretes a fluid containing enzymes that aids digestion in the duodenum
        
        it passes through the pancreatic duct
      - the liver secretes "bile", which also helps with digestion
        
        bile is alkaline so that the natural acidic mixture in the stomach can be neutralised
    - - it is a long tube running from the mouth to the anus
      - its walls contain muscles that relax and contract
        
        this is called "peristalsis"
      - it can be completely closed in certain points by "sphincter muscles"
      - it is lubrificated with mucus to help food slide
        
        it is secreted in "goblet cells" that are found in the lining of this canal
      - the mouth
        
        here, teeth bite and grind food, commencing physical digestion
        
        the tongue mixes food with saliva
        
        saliva is a mix of water,mucus and amylase
        
        saliva is produced in salivary glands
      - the large intestine
        
        it is divided into two parts
        
        the colon, which absorbs much of the water still in the food
        
        the rectum stores undigested food as faeces, which are then ejected through the anus
      - the oesophagus
        
        here, food slides down from the mouth into the stomach
        
        the hole in the middle of the oesophagus is called "lumen"
        
        the entrance to the stomach is closed by a sphincter muscle
      - the stomach
        
        it has strong, muscular walls that relax and contract to mix the food with enzymes and mucus
        
        these walls contain goblet cells, in addition to cells which produce enzymes (protease) and acid (pH 2, optimum for protease)
        
        the food here can sit for one or two hours until it is let into the duodenum
      - the small intestine
        
        it is the part of the alimentary canal between the stomach and the colon
        
        it is divided in two parts
        
        nearest to the stomach is the duodenum
        
        nearest to the colon is the ileum
        
        this is where nutrients and water are absorbed into the blood
- - - - large pieces of food are broken down into smaller ones
        
        this is done thanks to teeth
        
        the visible part of every teeth is enamel, which is the hardest substance produced by animals, but it can be dissolved by acids
        
        under enamel there is dentine, still very durable but not as enamel
        
        in the middle of the tooth there are nerves and blood
        
        the part of the tooth that is inside the gum is called "cement" and it has fibres growing out of it
      - this does not change the chemical composition of food
    - - the large molecules of food are broken down into smaller ones
        
        for example, amylase breaks down starch into maltose, which is then broken down to glucose thanks to maltase
        
        the protease in the stomach is called "pepsin", and is located inside the gastric juice, while that inside the duodenum is called "trypsin"
        
        since lipids are insoluble, bile emulsifies them into small droplets
- - - - it is here that maltase acts and many nutrients are absorbed by passing inside the blood capillaries
        
        all these blood capillaries join up and form the "hepatic portal vein", which takes all these substances to the liver