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DIGESTIVE SYSTEM
ANATOMY OF THE DIGESTIVE SYSTEM
The digestive system is used for breaking down food into nutrients which then pass into the
circulatory system and are taken to where they are needed in the body.
There are four stages to food processing:
Ingestion: taking in food
Digestion: breaking down food into nutrients
Absorption: taking in nutrients by cells
Egestion: removing any leftover wastes
The digestive system consists of a muscular tube, the digestive tract, also called the gastrointestinal
(GI), and composed:
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Mouth
Pharynx
Esophagus
Stomach
Small intestine and large intestine
Anus
Accessory digestive organs are outside the digestive tract, but they secrete substances which are
released into it.
 Salivary glands. These are six glands which release saliva into the mouth.
 Liver. It carries out important functions for the organism. It secretes bile, which is stored in
the gall bladder.
 Pancreas, which secrete pancreatic juice into small intestine.
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DIGESTIVE SYSTEM
DIGESTION
Digestion of food involves both mechanical and chemical processes.
Through digestion, large food particles are converted into smaller components that can be readily
absorbed into the bloodstream.
Mechanical digestion is simply the aspects of digestion achieved through a mechanism or
movement. There are two basic types of mechanical digestion.
mouth. Mastication (chewing) begins the process of breaking down food into nutrients. As a type
mechanical digestion, chewing our food is an important part of the digestive process because
smaller pieces are more readily digested through chemical digestion.
nical digestion also involves the process known as peristalsis. Peristalsis is
simply the involuntary contractions responsible for the movement of food through the esophagus
and intestinal tracts.
Chemical digestion involves those aspects of digestion achieved with the application of chemicals
to our food.
Digestive enzymes and water are responsible for the breakdown of complex molecules such as fats,
proteins, and carbohydrates into smaller molecules. These smaller molecules can then be absorbed
for use by cells.
The presence of these digestive enzymes accelerates the digestion process.
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DIGESTIVE SYSTEM
Mouth
In the mouth there are both mechanical digestion (teeth break down
food) and chemical digestion thanks to the saliva.
Begins when food enters the mouth.
It is physically broken down by the teeth.
It is begun to be chemically broken down by amylase, an enzyme in
saliva that breaks down carbohydrates
The tongue moves the food around until it forms a ball called a bolus.
The bolus is passed to the pharynx (throat) and the epiglottis makes
sure the bolus passes into the esophagus and not down the windpipe
PHARYNX
It is a channel common to the digestive and respiratory system. It
connects mouth with the esophagus, and nose to larynx. It has a flap,
the epiglottis, that closes over the respiratory tract to prevent food from
obstructing it.
OESOPHAGUS
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It is a muscular tube
It moves food by waves of muscle contraction called peristalsis.
It moves physically the food along to the stomach.
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DIGESTIVE SYSTEM
STOMACH
Food is temporarily stored here.
Gastric juices are secreted.
Stomach has layers of muscle that line the inside
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Chemical reactions take place in the stomach, breaking
down and dissolving its nutrients.
Digestion of proteins takes place in the stomach
SMALL INTESTINE
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Here continue the chemical reactions on the food. The chime is mixed with intestine juices,
bile and pancreatic juices and form the chyle.
Fats, carbohydrates and proteins are digested and then the absorption of nutrients takes
place here. It s walls have a folds called intestinal villi. These villi have very fine blood
vessels, the capillaries, through which the nutrients pass into the bloodstream.
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DIGESTIVE SYSTEM
LARGE INTESTINE AND ANUS
LARGE INTESTINE
 Its function is to absorb water
from the remaining indigestible
food matter
 The feces are formed here.
ANUS
 It is an opening at the end of the
digestive tract.
 Its function is to control the
expulsion of feces
SALIVARY GLANDS
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The salivary glands are glands with ducts, that
produce saliva.
They also secrete amylase, an enzyme that breaks
down starch into maltose, so in the mouth start the
digestion of carbohydrates.
PANCREAS
Pancreatic juice digests all major nutrient types
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Produces chemicals to help break down macromolecules
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Food does not go through the pancreas
LIVER
This is the largest organ in the body. It carries out
important functions for the organism.
 Produces bile, which is stored in the gallbladder, to help digest fat.
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DIGESTIVE SYSTEM
Complete this table:
Digestive
process
Complex
sugars
Action of saliva
in the mouth
They are cut
into smaller
fragments
Chemical digestion
Lipids (fats) Proteins
The remain
unaltered
They remain
unaltered
Water and
minerals
They remain
unaltered
Stomach
Small
intestine……
Large intestine
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