4. smooth muscle tissue

1. Smooth Muscle Tissue
•Smooth Muscle Tissue – The name
“smooth muscle” comes from the
fact that this muscle tissue lacks
the visible striations that are a
noticeable characteristic of the
other two muscle tissues, skeletal
and cardiac muscle.

2. •Smooth muscle fibers
contain numerous
myofibrils that are
oriented along the long
axis of the fiber, and
which extend from end
to end within the fiber.
These myofibrils are
composed of the same
thin myofilaments of
actin and myosin
contained in the other
muscle tissues, except
that they are arranged
in a more random
fashion.

3. •This means that
the thicker myosin
filaments do not
line up to produce
a “banded” or
“striped” look,
consequently,
smooth muscle
contains no
visible striations.
This is why it is
called non-
striated muscle
tissue.

4. •Smooth muscle is
located in the walls of
many internal organs
which is why it is
often called “visceral”
muscle. Organs such
as the stomach,
intestines, urinary
bladder, uterus,
arteries, veins, base of
hair follicles, and in
the iris of the eye are
all examples of organs
containing smooth
muscles in their walls.
smooth muscle in an artery wall

5. •Smooth muscle is therefore responsible
for the movement of food through the
digestive tract (called “peristalsis”), the
constriction of blood vessels, the
emptying of the bladder, the “labor”
pains of childbirth as well as for pushing
the baby out of the mother’s body, and
many more important bodily functions.

6. •Individual
smooth
muscle fibers
are elongated
with tapering
ends.

7. Can you see the elongated, tapered
fibers?

8. •Smooth Muscle
fibers are
arranged with
their tapered ends
overlapping so
they can form
different
functional
structures. These
functional
structures are
bundles, sheets,
or cords.

9. Bundles
Cord
Sheet

10. •As with
cardiac
muscle
tissue, each
smooth
muscle fiber
has a single,
oval shaped
nucleus
located in
the center of
the cell.

11. •Smooth muscle, unlike skeletal and
cardiac muscle, contracts very slowly,
maintains the contracted state for an
extended period of time, and relaxes
very slowly, even though the contraction
mechanism is identical to that of the
other two. As with cardiac muscle,
smooth muscle tends not to fatigue even
when the contracted state is held for a
long time. This is very different than
skeletal muscle.

12. •One additional important feature of
smooth muscle is that it can “stretch”
without causing an increase in the
internal pressure of the organ. This is an
important fact when one considers the
possibility of a “full” stomach, bladder,
intestine, or when a woman is pregnant
and the baby continues to grow inside
the uterus for up to nine months.

13. General Characteristics
1.Location –
Commonly found
in the walls of
internal organs

14. 2.Cell type or
description –
Elongated,
tapered fibers
arranged as
bundles, sheets,
or cords
What functional unit is this a picture of?

15. 3.Myofibril
arrangement-
least dense, yet still
run end to end within
the cell
random;
consequently no
visible striations
Notice the same actin & myosin as in
skeletal & cardiac muscle arranged in
the same sarcomere formation.

16. 4.Location of
nucleus
or nuclei –
One oval nucleus
located in the center
of the cell.
Note all the darkly stained nuclei

17. 5.Vascular Supply
and relative
rank-
-Good blood supply
when used, reduced
to minimal levels
when inactive, highly
variable with activity
-Ranks 3
rd
among
muscle tissues
Arrows pointing to capillaries

18. 6.Description of
contraction
and control
factor –
-Rhythmic, slow to
contract & relax,
holds contraction
without fatigue.
-Involuntary
contraction
7.Alternative
names –
Involuntary, non-
striated or
Visceral muscle

20. Longitudinal View (long Axis)
Note the elongated, tapered fibers, lack of striations, and single, centered nucleus

21. Another Longitudinal View
Note the elongated, tapered fibers, lack of striations, and single, centered nucleus

22. Cross-sectional View (short axis)
Dark areas are single centered nuclei that were cut through

23. Some slides include both views in one!!
Longitudinal section
Cross-section

24. A comparison of all three
Note the organs from which each type comes

25. A. C.
1.What tissue is “A”?
2.What tissue is “B”?
3.What tissue is “C”?
B.

26. •“A” was Skeletal Muscle Tissue.
•“B” was Smooth Muscle Tissue.
•“C” was Cardiac Muscle Tissue.
Did you get them right?

27. A.
B.
C.
Now, name the primary and a
secondary identifying characteristics
that are visible in each slide that
helped you name the tissue.
B.

28. •A hint here:
–The primary identifying characteristic
would be one that is visible and unique to
that tissue only.
–A secondary identifying characteristic is
one that is common to two, but when
combined with other visible traits,
assures the tissue’s identity.

29. A.
B.
C.
Here they are again.
B.

30. •Primary for “A” - multiple,
peripheral nuclei
•Secondary for “A” – dark
striations, or long, cylindrical
fibers
•Primary for “B” – no striations
at high magnification
•Secondary for “B” – single,
centered nucleus, elongated,
tapered fibers
•Primary for “C” – intercalated
discs
•Secondary for “C” –
branching, weaving network,
single, centered nucleus, or
light striations

31. Can you identify the two muscle tissues
in this slide?

32. Use primary identifying
characteristics to identify them.

33. smooth
cardiac

34. Identify each of the following:
A. B. C.