Cells
and
unite
to
form
tissues
,
and
tissues
combine
to
form
organs
.
-
A
tissue
is
a
group
of
cells
-
Common
origin
-
Function
together
to
carry
out
specialized
activities
-
Tissues
may
be
Hard
(
bone
)
,
(
fat
)
,
or
liquid
(
blood
)
-
Tissues
vary
tremendously
with
respect
to
the
kinds
of
cells
present
,
how
the
cells
are
arranged
,
and
types
of
fibres
present
(
if
any
)
.
-
Histology
is
the
science
that
deals
with
the
study
of
tissues
.
-
specialize
in
laboratory
studies
of
cells
and
tissue
for
diagnoses
Cells
combine
to
form
4
primary
tissues
which
contribute
to
homeostasis
by
providing
diverse
functions
including
protection
,
support
,
communication
between
cells
,
and
resistance
to
disease
.
tissue
-
Covers
body
surfaces
and
lines
organs
,
body
cavities
,
duct
,
and
forms
glands
.
Allows
body
to
interact
with
its
internal
and
external
environments
Connective
tissue
-
Protects
,
supports
,
and
binds
organs
,
stores
energy
as
fat
,
provides
immunity
Muscle
tissue
-
Generates
the
physical
needed
to
make
body
structures
move
and
generate
body
heat
Nervous
tissue
-
Detect
changes
in
body
and
outside
,
and
respond
by
generating
nerve
impulses
that
activate
muscular
contractions
and
secretion
Normally
,
most
cells
within
a
tissue
remain
anchored
to
other
cells
or
structures
.
Only
a
few
cells
such
as
move
freely
through
the
body
.
However
,
many
cells
migrate
extensively
during
the
growth
and
development
process
before
birth
.
A
germ
layer
is
a
group
of
cells
in
an
embryo
that
interact
with
each
other
as
the
embryo
develops
and
contribute
to
the
formation
of
all
organs
and
tissues
.
Tissues
of
the
body
develop
from
three
primary
germ
layers
:
Ectoderm
,
Endoderm
,
and
Mesoderm
Epithelial
tissues
develop
from
all
three
germ
layers
All
connective
tissue
and
most
muscle
tissues
derive
from
Nervous
tissue
develops
from
Epithelial
tissue
consists
of
cells
arranged
in
sheets
,
in
either
single
or
multiple
layers
-
Closely
packed
and
held
tightly
together
-
Covering
and
lining
of
the
body
-
Free
surface
3
major
functions
:
-
Selective
barrier
that
regulates
the
movement
of
materials
in
and
out
of
the
body
-
Secretory
surfaces
that
release
products
onto
the
free
surface
-
Protective
surfaces
against
the
environment
Epithelial
tissues
illustrate
a
basic
biological
principle
:
structure
closely
correlates
with
function
Surfaces
of
epithelial
cells
differ
in
structure
and
have
specialized
functions
-
(
free
)
surface
(
Faces
the
body
surface
,
body
cavity
,
lumen
,
or
duct
)
-
Lateral
surfaces
(
Faces
cells
)
-
Basal
surface
(
Opposite
of
apical
layer
and
adhere
to
materials
)
Rest
on
a
Basement
membrane
Thin
double
extracellular
layer
that
serves
as
point
of
attachment
and
support
for
overlying
epithelial
tissue
Consists
of
:
a
)
lamina
-
Closer
to
and
secreted
by
the
epithelial
cells
-
Contains
laminin
,
collagen
,
glycoproteins
,
and
b
)
Reticular
-
Closer
to
the
underlying
connective
tissue
-
Contains
collagen
secreted
by
the
connective
tissue
cells
features
of
epithelial
tissue
:
-
Own
nerve
supply
-
Avascular
or
its
own
blood
supply
-
Blood
vessels
in
the
adjacent
connective
tissue
bring
in
nutrients
and
eliminate
waste
(
exchange
is
by
diffusion
)
-
High
rate
of
cell
division
for
renew
and
repair
-
Numerous
roles
in
the
body
(
i
.
e
.
protection
and
)
Two
main
types
of
epithelial
tissue
:
1
-
Covering
and
lining
epithelium
(
)
a
)
Outer
covering
of
skin
and
some
internal
organs
b
)
Inner
lining
of
blood
vessels
,
ducts
and
body
cavities
,
and
interior
of
respiratory
,
digestive
,
urinary
and
reproductive
systems
.
2
-
Glandular
epithelium
a
)
Secreting
portion
of
glands
(
thyroid
,
adrenal
,
and
sweat
glands
)
Normally
classified
according
to
:
-
Arrangement
of
cells
into
layers
-
Shapes
of
cells
see
the
pictures
!
!
!
Arrangement
of
cells
in
layers
-
Consist
of
one
or
more
layers
depending
on
function
Simple
epithelium
(
Single
layer
of
cells
that
function
in
diffusion
,
osmosis
,
filtration
,
secretion
,
or
absorption
)
epithelium
(
Appear
to
have
layers
because
cell
nuclei
at
different
levels
;
All
cells
reach
basement
membrane
but
not
all
reach
the
apical
surface
;
Cells
that
reach
apical
surface
may
contain
cilia
or
secrete
mucus
(
e
.
g
.
goblet
cells
)
)
Stratified
epithelium
(
Two
or
more
layers
of
cells
that
protect
underlying
tissues
in
areas
of
wear
and
tear
)
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