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nutrition in humans - Coggle Diagram

- - - - physical digestion
        
        (chewing action of teeth) smaller pieces → increase SA:V for salivary amylase to work on
        
        saliva also keeps the mouth moist & moistens food so its easier to swallow
      - chemical digestion
        
        (salivary amylase → breaking down starch to maltose)
        
        opt: pH7
      - tongue
        
        taste buds (identify & select suitable foods), mixes food with saliva, roll food into bolus (small slippery round masses)
  - - - contains 2 layers of muscles
        which work antagonistically
        
        longitudinal (outer side)
        
        longitudinal contract, circular relax → gut dilates, it becomes wider & shorter. widens lumen for food to enter
        
        circular (inner side)
        
        circular contract, longitudinal relax → lumen narrow and longer. food is squeezed or pushed forward
        
        both sets of muscles produce long slow contractions which move food along the gut via peristalsis
        
        enables food to be mixed with the digestive juices, and also pushes or propels the food along the gut
    - - peristalsis: rhythmic, wave-like muscular contractions in the wall of the alimentary canal
  - - - functions
        
        store food
        
        protein digestion
        
        churning
        
        kill microorganisms ((HCl acids)
    - - peristalsis by stomach muscles - churning food - further physical digestion, mix food with gastric juice
    - - provide acidic environment for pepsin to work (proteins → peptones) [opt: pH 2/3]
  - - - does not secrete the enzymes
        
        receives pancreatic juice from the pancreas via the pancreatic duct
        
        has all 3 enzymes (pancreatic amylase, lipase, tryspin)
        
        receives bile from the bile duct
        
        pH 8-9 (alkali)
        
        pancreatic & bile juice have sodium hydrogen carbonate ions which creates the alkaline medium
    - - absorbs digested food
        
        intestinal gland
        
        ~juice, lipase, erepsin, lactase, maltase
      - mineral salts are also absorbed in the ileum
      - most enzymes here (the different glands & mucus)
    - - → connected to the stomach by the pyloric sphincter in the pylorus
        
        → main function is to further chemically digest food
        
        → lining of the walls contain glands which secrete digestive enzymes & is also adapted to absorb digested food products & water
    - - large SA:V
        
        ^rate of absorption of food subs
        
        inner surface is highly folded
        
        folds bear numerous minute finger-like projections (villi)
        
        villi have thin walls/membrane - epithelium cells (one cell thick)
      - membranes that separate food subs from blood are thin
        
        reduces diffusion distance, faster
      - long to provide sufficient time for absorption
      - richly supplied with blood capillaries & lymphatic capillaries to carry away absorbed food subs
        
        (the continued removal maintains a concentration gradient for absorption, each villus has a network)
    - - glucose & aa (diffusion & AT thru blood capillaries of villi)
      - glycerol + fatty acids (diffuse into epithelium, combine to form minute fat globules which enter lacteals)
  - - - connecting the LI to the anus, receive stool from the colon (lets yk that there is stool to be evacuated, holds it at first) → mucus glands (protective layer against the bacteria)
    - - small tube like structure is attached to the first part of the LI (also called the colon), no proper defined roles in the immune system
    - - pouch within the peritoneum that is considered to be the beginning of the large intestine
    - - The longest part of the large intestine
    - - absorb water & electrolytes (help body regulate chem reactions)
      - producing and absorbing vitamins
      - forming and propelling feces toward the rectum for elimination
        
        removal is called egestion/defecation
    - - control the expulsion of feces
        for the feces to pass through, before exiting the body
      - undigested & unabsorbed matter is stored temporarily mainly here
- - - - 1st source is hepatic artery (delivers blood from the heart)
        
        2nd is hepatic portal vein (delivers blood from the intestines) → sugars & aa
    - - production of bile
        
        bile salts
        
        emulsify fats - breakdown fats into small globules/droplets
      - iron storage
        
        bile pigment (haemoglobin broken down into bilirubin (waste product) → must be get rid from the body → follow faeces out
      - protein synthesis
        
        synthesised proteins found in blood plasma from aa in the diet (e.g. prothrombin & fibrinogen)
        
        regulates blood clotting
      - deamination of aa
      - detoxification (alcohol)
  - - - endocrine
        
        Regulates blood sugar by creating and releasing important hormones directly into the bloodstream (insulin & glucagon)
        
        → without duct
        → secrete hormones
      - exocrine
        
        Helps in digestion by producing enzymes including trypsin, chymotrypsin, amylase & lipase
        
        → ducted gland
        
        → pancreatic duct
        
        → digestive enzymes
- - - - transported to liver by hepatic portal vein
        
        capillaries at both ends
      - uptake & use of food
      - sugar + aa (SI) and water + mineral salts (LI)
        
        glucose:
        
        in liver & muscles, excess are converted into glycogen for storage (6h)
        
        excess glycogen is turned into fats for storage
        
        aa:
        
        excess is not stored --> deamination
        
        amino group -> ammonia (gas), taken into cells as its highly soluble, can change pH
        
        converted into urea (not toxic, excreted in urine)
        
        carbon residue --> glucose --> glycogen for storage