The
is
among
the
most
important
digestive
organs
and
is
located
behind
the
stomach
The
is
the
heaviest
and
largest
gland
in
the
human
body
and
is
formed
of
four
lobes
.
The
hard
and
soft
palates
form
the
roof
of
the
and
the
pour
their
secretions
into
the
during
the
oral
phase
of
digestion
.
At
the
,
the
diameter
of
the
GI
tract
increases
to
form
a
hollow
sac
-
like
structure
made
of
three
layers
of
smooth
muscle
.
These
muscles
are
arranged
in
longitudinal
,
diagonal
and
circular
layers
.
The
is
among
the
most
important
digestive
organs
and
is
located
behind
the
.
It
secretes
a
large
number
of
enzymes
,
involved
in
the
digestion
of
carbohydrates
,
fats
,
and
proteins
.