Transcript ball and bile

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
• Chewing:
The Mouth: Mechanical
– 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:
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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?
– 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:
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?
– 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
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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!
• How can we reduce tooth decay?
1) Fluoride in water and
toothpaste
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Strengthens enamel of teeth by
resisting bacteria acid
Not done in Asia…Thoughts?
2) Brush BEFORE meals, not after
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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
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Bacteria can hide in space between
gums and teeth
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
• 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
• 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
• Glands in stomach
release Gastric juices
(Pepsin and HCl)
• 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” 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
• 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
• 6 m long but only 2.5 cm wide; covers 9m2
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
• 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
• After absorption, food
molecules are assimilated
• Assimilation to become a
useful part of a cell or organ
• 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
• 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
• 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)