1. Temple University School of Medicine
Muscle
Laboratory
Thomas A. Marino, Ph.D.
Albert Lamperti, Ph.D.
Marvin Sodicoff, Ph.D.

2. Objectives
To be able to recognize and understand
how skeletal, smooth and cardiac
muscle is organized so that it functions
properly.
To be able to identify the subcellular
organization of the different types of
muscle.

3. Slide 26
Image 1/5
Skeletal muscle - Longi. sections, Low, Med., High mags.
Skeletal muscle cells are multinucleated and do not branch but rather have a
relatively straight course. Their nuclei are located at the periphery of the
cell (not seen well here). Cross-striations are an obvious characteristic of
skeletal muscle cells.

4. Slide 27
Image 1/4
Skeletal Muscle - Cross Sections, Low, Medium, High mags
Polygonally-shaped cross sections of skeletal muscle cells demonstrate their
peripherally placed nuclei just under the sarcolemma (cell membrane).
Endomysial connective tissue surrounding each muscle cell contains blood
vessels with their endothelial cells.

5. Slide 27, Image 2/4
Skeletal muscle - low & high mag
The connective tissue that surrounds: 1. the muscle bundle is the epimysium,
a dense irregular connective tissue, 2. a fascicle of muscle fibers is the
perimysium, 3. the muscle fiber is the endomysium . The endomysium
is made up of reticular fibers.

6. Slide 27 Image 3/4
Skeletal muscle - high mag.
Neuromuscle spindles in cross section have small intrafusal muscle fibers
surrounded by a connective tissue sheath. The larger extrafusal muscle
fibers surround the spindle. Compare the muscle spindle to the small
nerve bundle below it.

7. Slide 27
Image 4/4
Skeletal muscle, muscle spindle - high mag.
The intrafusal muscle fibers are small striated skeletal muscle fibers which
lie in a fluid-filled space which is surrounded by the connective tissue
capsule. Sensory and motor nerves end on these intrafusal muscle fibers.

9. EM
Skeletal muscle
Longitudinal
Section
At the fine structural level it is easier to see the A and I
bands. I bands are divided by Z lines. A sarcomere runs
from one Z line to the next. A series of sarcomeres that run
the length of the muscle fiber is called a myofibril. The A
band is divided by the H band which in turn is divided by the
M line. The H band is the region where only myosin exists.
The I band is the region where only actin exists.

11. EM 2
Skeletal muscle
In cross sections of myofibrils
, you can see cross
sections of actin and
myosin filaments.
Depending where along the
sarcomere you make your
section, determines whether
you will see just actin
filaments, actin and myosin
filaments or only myosin
filaments. Also note the
mitochondria in the field.

12. Slide 99 Image 1/2
Tongue, low mag.
Deep to the stratified squamous epithelium that covers the tongue is skeletal
muscle that is composed of small muscle cells that are arranged in a variety o
planes.

13. Slide 99
Image 2/2
Tongue, high mag.
At higher magnification you can see skeletal muscle cells that are cut in all
different directions. Here note the multiple nuclei in the muscle fibers.

15. Slide 17
Image 1/1
Pubic symphysis - low magnification
Skeletal muscle inserts into the dense fibrous connective tissue that
surrounds bone and cartilage - the periosteum and the perichondrium,
respectively.

16. Slide 26
Image 3/5
Cardiac Muscle - Longi Sections, Low, Medium, High mags
Cardiac muscle like skeletal is striated though the striations are usually not as
well defined. In addition, individual cardiac muscle cells are branched and
have centrally located nuclei (may be binucleate). The endomysial
connective tissue carries the richest blood supply of all three muscle types.

17. Slide 26,
Image 4/5
Cardiac Muscle - cross section, very low - high mags.
In cross section the centrally placed nuclei and the variety of sizes of the
sectioned cells are seen. Due to branching cardiac muscle cells cut in
cross section do not appear as homogeneous in size and shape as
skeletal muscle cells.

18. Slide 68 Image 1
Cardiac muscle -high mag
The striations of the branching cardiac muscle cells as well as the
intercalated disks can be seen. Just like skeletal muscle, cardiac muscle
has A, I, and H bands as well as M and Z lines.

20. EM
Cardiac
muscle
In cardiac muscle, the cells connect to one another via intercalated disks.
These disks consist of junctional complexes that include: gap junctions,
desmosomes, and fasciae adherentes.

21. Slide 32
Image 1/4
Cardiac muscle -low magnification
Just under the endocardium is a layer of connective tissue that contains
Purkinje cells, cells of the cardiac conduction system. Deep to the
Purkinje cells locate the myocardium composed of cardiac muscle cells.

22. Slide 32
Image 2/4
Cardiac muscle -higher magnification
The typical characteristics of ordinary cardiac muscle cells include the
branching as well as centrally placed nuclei. In contrast Purkinje cell
cytoplasm stains more lightly due to fewer organelles and large
accumulations of glycogen . These are also bigger cells.

23. Slide 32
Image 3/4
Cardiac muscle -high magnification
This high power view of Purkinje cells demonstrates the lighter cytoplasmic
staining of these cells due to fewer organelles and marginal myofibrils. It is
also possible to find binucleate Purkinje cells. Also note the prominent
nucleolus in these Purkinje cells.

24. Slide 32
Image 4/4
Another characteristic of cardiac muscle tissue is the intercalated disk, a
region where two cardiac muscle cells contact each other via junctional
complexes. This band is a region where the adjacent cell membranes and
their junctions stain darkly.
Cardiac muscle -high magnification

26. Slide 26,
Image 5/5
Smooth Muscle - cross & longi section, very low - high mags
In the wall of the small intestine smooth muscle is cut in cross and
longitudinal sections. Smooth muscle cells are the smallest of the muscle
cell types. They are fusiform in shape and have centrally-placed nuclei.
They do not have the characteristic cross striations seen in cardiac and
skeletal muscle.

27. Slide 119 Image 1/1
Duodenum
low & medium mag.
The epithelial lining of the duodenum is located internal to the smooth
muscle. Smooth muscle is a major component of the wall of the intestines.
Smooth muscle cells in the outer longitudinal layer are cut in cross
section and those in the inner circular layer are cut longitudinally. In
between these layers of smooth muscle (bracket) can be found blood
vessels, nerves and connective tissue elements.

28. Slide 74
Image 1/1
Artery Low mag.
A muscular artery has a
smooth muscle layer
surrounding the vessel
lumen. In the two images
you can see the smooth
muscle cells cut in cross
and longitudinal section.
Note the appearance of the
smooth muscle cells
embedded in the
connective tissue matrix.

29. Slide 126 Image 1/1
Anal Canal - med. & high mag.
This section, stained with a trichrome stain, distinguishes smooth muscle
from connective tissue. Note the smooth muscle cells surrounding the
lumen of the blood vessel. Smooth muscle interweaves with the
connective tissue deep to the underlying the simple columnar
epithelium lining the anal canal.

30. Slide 156
Image 1/1
Uterine Tube - low. & med. mag.
This section, routinely stained with H & E, demonstrates that it is possible to
distinguish smooth muscle from connective tissue. Smooth muscle
surrounds the lumen of the small arteries. Smooth muscle interweaves
with the connective tissue deep to the underlying the simple columnar
epithelium lining the uterine tube.

31. Slide 61
Image 1/1
Esophagus - low
& high mag
The muscular wall of the
middle 1/3 of the
esophagus, is a
mixture of smooth and
skeletal muscle.
Both stain pink, but
smooth muscle has
more nuclei per unit
area and skeletal
muscle cells have
peripheralized nuclei
and are striated.

32. Demo
Muscle, 3 types - high mag.
In this composite slide are cross and
longitudinal sections of all three types
of muscle. Based primarily on the
location of the nuclei, the presence or
absence of striations and the size and
shape of the cell, it is possible to
distinguish these cell types.