The digestive system
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The Digestive System. Feed Me!. Digestive system uses mechanical and chemical energy to break organic material Material is absorbed into the cells of our bodies; used to make energy or other molecules Mechanical: Grinding, smashing tearing, crushing Chemical: Enzymes and Acidic solutions.

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Feed me
Feed Me!

  • Digestive system uses mechanical and chemical energy to break organic material

  • Material is absorbed into the cells of our bodies; used to make energy or other molecules

  • Mechanical:

    • Grinding, smashing tearing, crushing

  • Chemical:

    • Enzymes and Acidic solutions

The mouth mechanical
The Mouth: Mechanical

  • Chewing:

    • Tearing and grinding food into small lumps; increase surface area for enzyme activity

  • Teeth:

    • Strongest bones in the body; 32 in a normal mouth

    • Incisorscutting food; 8

    • Caninestearing food; 4

    • Premolars grinding food; 8

    • Molarsgrinding food ; 12

  • Tongue:

    • Strongest muscle in the body

    • Pushes food down esophagus

    • Taste food

    • Wet area for chemical digestion


  • How many sets of teeth do we have?

    • 2; milk teeth (fall out) and permanent teeth

  • Wisdom teeth last molars to form (may never form)

    • Ruins teeth placement in many people (mouth too small)

    • Removed surgical

  • Parts of a tooth:

  • Crown part of tooth above gums

  • Gums flesh around jaw bone

  • Enamel hard outer layer; easily scrubbed away if weakened

  • Dentine soft, bone-like middle of tooth

  • Root blood vessels/nerves keeping tooth alive

  • Cement strong material holding tooth to jaw

Tooth pain is the worst pain
Tooth Pain is the WORST Pain

  • Why do we brush our teeth?

    • Reduce bad breath

    • Reduce tooth decay

    • Reduce gum disease

  • What causes all these?

    • Bacteria living on our teeth; eating mashed food

    • Bacteria produce acid as they eat; slowly breakdown enamel

  • Plaque sticky layer of food and bacteria

  • Cavity holes in teeth from tooth decay

  • Pulp cavity decay reaches root; extremely painful!

The war against plaque
The War Against Plaque!

  • How can we reduce tooth decay?

  • Fluoride in water and toothpaste

    • Strengthens enamel of teeth by resisting bacteria acid

    • Not done in Asia…Thoughts?

  • Brush BEFORE meals, not after

    • After meals your mouth acidity is much higher, so the enamel is weak; must wait 30 mins!

    • Brushing after can make teeth decay faster

  • Brush your gums

    • Bacteria can hide in space between gums and teeth

The mouth chemical
The Mouth: Chemical

  • Salivary glands:

    • Hidden under tongue

    • Release mucus (watery solution) and enzymes to help breakdown food

  • Amylase:

    • Enzyme that breaks down starch into di and monosaccharaides

  • Bolus:

    • Ball of mashed food

  • Taste buds:

    • Alert us to nutrients we need to consume

    • Sugar Sweet

    • Acids Sour

    • Toxins Bitter

    • Salts Salty

    • Protein Umami

The o esophagus
The (O)Esophagus

  • Swallowing pushes food down the esophagus to the stomach

  • Peristalsis:

    • Contractions of muscle waves move food in one direction

  • Food has to pass by the trachea (entrance to the lungs) so a small cartilage cover (epiglottis) blocks the opening

  • Eating too fast can send food “Down the Wrong Pipe”

The stomach mechanical
The Stomach: Mechanical

  • Walls of stomach contract to crush food and help mix food with digestive juices

  • Pyloric Sphincter muscular ring at exit of stomach that lets a small amount of digested food (chyme) through at a time

  • Why?

    • Too much acidic liquid in the intestine at one time will damage it

The stomach chemical
The Stomach: Chemical

  • Glands in stomach release Gastric juices (Pepsin andHCl)

  • Pepsin breaks down proteins into amino acids

  • HCl keeps the stomach at a pH 2!

  • Food can take up to 4 hours to digest; become chyme

  • Why doesn’t HCl eat through the stomach?

    • Lining of stomach makes protective mucus

Heart burn and stomach ulcers
Heart Burn and Stomach Ulcers

  • “Heart Burn” is when stomach acid gets into the esophagus and causes a burning feeling in the chest

  • Caused by spicy food

  • Stomach Ulcer is a hole in the stomach lining which can cause major health problems

  • Caused by high acidic levels

The small intestine chemical
The Small Intestine: Chemical

  • Duodenum (first 25cm)

    • Pancreas releases enzymes to:

      • Amylase: Starch  Maltose

      • Trypsin: Proteins Peptides

      • Lipase: Fats Fatty Acids

      • NaHCO3 to neutralize stomach acid

    • Liver releases bile to:

      • Break apart fat globs (emulsify)

      • Neutralize pH

    • Gallbladder releases extra bile when needed

  • Ileum second round of enzymes to finish digestion; absorption

The small intestine mechanical
The Small Intestine: Mechanical

  • 6 m long but only 2.5 cm wide; covers 9m2How does this fit inside you?

    • Villi folds on the intestine membrane; one cell thick so absorption can occur

  • Peristaltic contractions move food through intestine and continue to break down food

  • Food is absorbed into the blood through villus

  • Lacteals absorb fatty acids/glycerols into lymph which carries it to blood in heart

  • Capillaries absorb sugars and amino acids

  • Hepatic portal vein transfer food molecules to liver

You ate it now use it
You Ate It, Now Use It

  • After absorption, food molecules are assimilated

  • Assimilation to become a useful part of a cell or organ

  • Liver

  • Glycogen is made from excess blood glucose

  • Amino acids used to make proteins

  • Fatty acids/glycerols are made into fat

  • Form cholesterol from fat

  • Excess amino acids deaminated

Liquid waste
Liquid Waste

  • Excess water, vitamins, minerals, drugs and toxins are removed as urine

  • Most of urine is Urea

  • Deamination excess amino acids cannot be stored, so liver removes the amino group (NH2) to make sugars and fats

    • NH2 becomes ammonia (NH3)

    • NH3 joins CO2 to make Urea

    • Urea is toxic, so it is filtered from the blood by the kidneys

The large intestine
The Large Intestine

  • Only 1.5m long but 6.5cm wide

  • Indigestible material is compacted as much water as possible is absorbed back into the body

  • Anaerobic bacteria produce vitamins B and K for us while digesting the material

  • After 18-24 hours, waste is removed from the body as feces

  • Passes through the last part of the digestive system, the rectum (the butt)

    • Anus releases feces (egestion)