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The process of
breaking down food
into molecules the
body can use is called
digestion.
Digestion occurs in the
gastrointestinal tract,
or digestive tract,
which is a long tube
which begins at the
mouth and winds
through the body to
the anus.
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Digestion includes
the mechanical and
chemical
breakdown of food
into nutrients
• Mechanical digestion
begins when the teeth
cut and grind food.
• The tongue also aids in
mechanical digestion
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Saliva is produced
by the salivary
glands to begin
chemical digestion
of food.
Salivary amylase is
the chemical in
saliva that begins
the chemical
digestion
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The pharynx is an
open area that
begins at the back
of the mouth, and
serves as a
passageway for
both air and food.
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food is then forced
from the pharynx
into the esophagus.
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The stomach is an organ involved in both
mechanical and chemical digestion.
It is located in the upper left side of the
abdominal cavity, just below the diaphragm.
Mechanical
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The stomach has three
layers of smooth
muscle—a circular layer,
a longitudinal layer, and
a diagonal layer.
These muscles churn the
food within the stomach
and help to carry out
mechanical digestion.
Chemical
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Gastric fluid carries out
chemical digestion in the
stomach.
Gastric fluid is a liquid
that is secreted by the
gastric glands in the
stomach.
Hydrochloric acid within
the gastric fluid helps
dissolve food and
minerals and keep
bacteria at bay.
The liver produces bile, which is
vital to digesting fats.
It also stores glucose, makes
proteins, and breaks down toxic
substances.
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The gallbladder is a saclike organ that stores
and concentrates bile.
The gallbladder releases the bile through a
common bile duct into the small intestine.
• The pancreas has two roles in digestion
• The first role it plays is to increase the pH
of the stomach acid by producing sodium
bicarbonate.
• The second role it plays is to secrete
enzymes that help to further break down
carbohydrates, proteins, lipids and
nucleic acids.
It is also responsible for secreting the
hormones insulin and glucagon
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The chyme from the
stomach will further
break down in the
small intestine.
Absorption occurs
mostly in the small
intestine.
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Once absorption is complete in the small
intestine, peristalsis will move the remaining
contents into the colon or large intestine.
The colon initiates contractions that move the
material out of the body.
As nutrients and water are absorbed from the
matter in the colon, the matter solidifies into
feces.
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The nervous system includes two major divisions.
The first division is the central nervous system
and is made up of the brain and the spinal cord.
The brain is the control center of the nervous
system.
The spinal cord carries nerve signals between the
body and the brain.
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The second division is the peripheral nervous
system that sends information to and from
the central nervous system.
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Somatic Nervous System
The somatic nervous system contains motor
neurons that control the movement of
skeletal muscles.
The somatic system is considered voluntary,
but can operate without conscious control.
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Somatic system also
relays the signals in
reflexes.
Reflexes are
involuntary and often
self-protective
movements. An
example is the
patellar, or kneejerk, reflex.
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Autonomic Nervous System
The autonomic nervous system controls
internal body conditions by regulating
smooth muscles in blood vessels and organs.
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The sympathetic
division prepares
the body when
activated by
physical or
emotional stress.
For example, pupils
dilate and heart
rate increases.
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The
parasympathetic
division controls
the internal
environment during
routine conditions.
For example, pupils
constrict and heart
rate decreases.
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Cerebrum- largest part of the brain, divided
into two hemispheres
The two hemispheres are divided into four
lobes: the frontal, parietal, temporal, and
occipital
Through years of study scientists have
determined how and where various functions
are localized in the brain.