The Digestive System

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

The Mouth: Mechanical Chewing: Chewing: – Tearing and grinding food into small lumps; increase surface area for enzyme activity Teeth: 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: Tongue: – Strongest muscle in the body – Pushes food down esophagus – Taste food – Wet area for chemical digestion

Smile! How many sets of teeth do we have? 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) Wisdom teeth  last molars to form (may never form) – Ruins teeth placement in many people (mouth too small) – Removed surgical Parts of a tooth: Parts of a tooth: 1)Crown  part of tooth above gums 2)Gums  flesh around jaw bone 3)Enamel  hard outer layer; easily scrubbed away if weakened 4)Dentine  soft, bone-like middle of tooth 5)Root  blood vessels/nerves keeping tooth alive 6)Cement  strong material holding tooth to jaw

Tooth Pain is the WORST Pain Why do we brush our teeth? Why do we brush our teeth? – Reduce bad breath – Reduce tooth decay – Reduce gum disease What causes all these? 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 Plaque  sticky layer of food and bacteria Cavity  holes in teeth from tooth decay Cavity  holes in teeth from tooth decay Pulp cavity  decay reaches root; extremely painful! Pulp cavity  decay reaches root; extremely painful!

The War Against Plaque! How can we reduce tooth decay? How can we reduce tooth decay? 1)Fluoride in water and toothpaste  – Strengthens enamel of teeth by resisting bacteria acid – Not done in Asia…Thoughts? 2)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 3)Brush your gums  – Bacteria can hide in space between gums and teeth

The Mouth: Chemical Salivary glands: Salivary glands: – Hidden under tongue – Release mucus (watery solution) and enzymes to help breakdown food Amylase: Amylase: – Enzyme that breaks down starch into di and monosaccharaides Bolus: Bolus: – Ball of mashed food Taste buds: Taste buds: – Alert us to nutrients we need to consume – Sugar  Sweet – Acids  Sour – Toxins  Bitter – Salts  Salty – Protein  Umami

The (O)Esophagus Swallowing pushes food down the esophagus to the stomach Swallowing pushes food down the esophagus to the stomach Peristalsis: 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 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” Eating too fast can send food “Down the Wrong Pipe”

The Stomach: Mechanical Walls of stomach contract to crush food and help mix food with digestive juices 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 Pyloric Sphincter  muscular ring at exit of stomach that lets a small amount of digested food (chyme) through at a time Why? Why? – Too much acidic liquid in the intestine at one time will damage it

The Stomach: Chemical Glands in stomach release Gastric juices (Pepsin and HCl) Glands in stomach release Gastric juices (Pepsin and HCl) Pepsin breaks down proteins into amino acids Pepsin breaks down proteins into amino acids HCl keeps the stomach at a pH 2! HCl keeps the stomach at a pH 2! Food can take up to 4 hours to digest; become chyme Food can take up to 4 hours to digest; become chyme Why doesn’t HCl eat through the stomach? Why doesn’t HCl eat through the stomach? – Lining of stomach makes protective mucus

Heart Burn and Stomach Ulcers “Heart Burn” is when stomach acid gets into the esophagus and causes a burning feeling in the chest “Heart Burn” is when stomach acid gets into the esophagus and causes a burning feeling in the chest Caused by spicy food Caused by spicy food Stomach Ulcer is a hole in the stomach lining which can cause major health problems Stomach Ulcer is a hole in the stomach lining which can cause major health problems Caused by high acidic levels Caused by high acidic levels

The Small Intestine: Chemical Duodenum (first 25cm)  Duodenum (first 25cm)  – Pancreas releases enzymes to: Amylase: Starch  Maltose Amylase: Starch  Maltose Trypsin: Proteins  Peptides Trypsin: Proteins  Peptides Lipase: Fats  Fatty Acids Lipase: Fats  Fatty Acids NaHCO 3 to neutralize stomach acid NaHCO 3 to neutralize stomach acid – Liver releases bile to: Break apart fat globs (emulsify) Break apart fat globs (emulsify) Neutralize pH Neutralize pH – Gallbladder releases extra bile when needed Ileum  second round of enzymes to finish digestion; absorption Ileum  second round of enzymes to finish digestion; absorption

The Small Intestine: Mechanical 6 m long but only 2.5 cm wide; covers 9m 2 How does this fit inside you? 6 m long but only 2.5 cm wide; covers 9m 2 How 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 Peristaltic contractions move food through intestine and continue to break down food Food is absorbed into the blood through villus Food is absorbed into the blood through villus Lacteals  absorb fatty acids/glycerols into lymph which carries it to blood in heart Lacteals  absorb fatty acids/glycerols into lymph which carries it to blood in heart Capillaries  absorb sugars and amino acids Capillaries  absorb sugars and amino acids Hepatic portal vein  transfer food molecules to liver Hepatic portal vein  transfer food molecules to liver

You Ate It, Now Use It After absorption, food molecules are assimilated After absorption, food molecules are assimilated Assimilation  to become a useful part of a cell or organ Assimilation  to become a useful part of a cell or organ Liver  Liver  1)Glycogen is made from excess blood glucose 2)Amino acids used to make proteins 3)Fatty acids/glycerols are made into fat 4)Form cholesterol from fat 5)Excess amino acids deaminated

Liquid Waste Excess water, vitamins, minerals, drugs and toxins are removed as urine Excess water, vitamins, minerals, drugs and toxins are removed as urine Most of urine is Urea Most of urine is Urea Deamination  excess amino acids cannot be stored, so liver removes the amino group (NH 2 ) to make sugars and fats Deamination  excess amino acids cannot be stored, so liver removes the amino group (NH 2 ) to make sugars and fats – NH 2 becomes ammonia (NH 3 ) – NH 3 joins CO 2 to make Urea – Urea is toxic, so it is filtered from the blood by the kidneys

The Large Intestine Only 1.5m long but 6.5cm wide Only 1.5m long but 6.5cm wide Indigestible material is compacted as much water as possible is absorbed back into the body 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 Anaerobic bacteria produce vitamins B and K for us while digesting the material After hours, waste is removed from the body as feces After hours, waste is removed from the body as feces Passes through the last part of the digestive system, the rectum (the butt) Passes through the last part of the digestive system, the rectum (the butt) – Anus releases feces (egestion)