Digestion
Ch 35.1
Pages 946-953
The Function of the
Digestive System
To disassemble the food you
eat into its component
molecules for use in your
body as energy.
Is like a disassembly line
Mechanical and Chemical Digestion
Mechanical digestion –
the physical process of
physically breaking down
food into smaller pieces.
Chemical Digestion – the
chemical process of
breaking down food with
the use of enzymes.
Step 1 – The Mouth
Mechanical Digestion occurs
when you chew, this
prepares food for chemical
digestion.
Chemical Digestion occurs
when saliva in the mouth
contains an enzymes called
amylase that breaks down
starch into di or
monosaccharide.
Step 2 – Swallowing Food
Tongue shapes food into a ball and
swallowing forces food into the
esophagus.
Esophagus – muscular tube
connects mouth to stomach.
Food moves down by peristalsis – a
series of involuntary smooth muscle
contractions along walls of digestive tract.
Epiglottis – Flap that closes over the
opening to the respiratory tract as you
swallow (so food doesn’t go down the
wrong way), after food passes epiglottis
opens again.
Step 3 – The Stomach
Stomach – Muscular pouch like
enlargement of the digestive tract.
Mechanical digestion in the stomach by
muscular churning – muscles contract
breaking down food.
Chemical Digestion in the stomach by
the secretion of gastric juices that
contain HCl and Pepsin (enzyme that
begins the digestion of proteins in food).
Food stays in stomach 2-4 hours and is
liquid by the time it leaves the stomach
to go to the small intestine.
Step 4 - The Small Intestine
Small intestine – is named
small because it is narrow.
Digestion is completed in the
small intestine by muscle
contractions and chemical
digestion (amylase). The
pancreas and liver help with
chemical digestion as well.
Liquid food is absorbed by the
small intestine, indigestible
material moves onto large
intestine.
Pancreas and Liver
Pancreas – soft flattened
gland secretes digestive
enzymes and hormones.
Breaks down carbs,
proteins and fats.
Liver – Large, complex
organ that produces bile
that is stored in your gall
bladder.
Bile – Chemical substance
that helps break down fat.
Step 5 – Large Intestine
Indigestible material passes to
large intestine (into a
muscular tube called the
colon).
Large intestine absorbs water
and eliminates waste out by
feces.
Process of digestion takes 24-
33 hours.