SKELETAL AND CARDIAC MUSCLE LABORATORY
Skeletal muscle (longitudinal and cross section in slide #8)
Examine the cross section first to see various layers of
connective tissue (epimysium, perimysium and endomysium) Muscle tissues shrink
considerably during fixation so learn to discern (nice rhyme, huh!??)
shrinkage artifact which shows up "well" on this slide. You will also note some small
nerves and blood vessels in the connective tissue regions.
From the capillary density, can you make an educated guess
(aka, "diagnosis") as to what the majority type skeletal muscle fibers are in this
sample?
Note the generally peripheral location of the nuclei in cross
sectioned fibers. How does their position differ from that in cardiac myocardial
cells which you'll see in the next slide?
Don't confuse skeletal muscle bundles with peripheral nerve.
Why is muscle so eosinophilic?
Now look at the longitudinal section on the slide. Do you see
striations across the myofibrils? (Hint: You'd better!!!) Lower your scope's
condenser to make these stand out. Look at a good section at high mag and while carefully
focussing up and down you should make out A band, I band and Z band. These show up
even better on slide #24. Have a look there, too.
Be sure you can easily identify striated muscle as it may turn
up in places you wouldn't expect as in your slide of tonsil.
Cardiac muscle (slide #80, heart)
Try to find an area of good longitudinal representations of
cardiac cells. Note that the nuclei are centrally located contrary to that of
skeletal muscle fibers. Myocardial cells abut each other at intercalated disks. If you
can't differentiate these well look at the demonstration scope set up in the front
of the lab (demonstration slide #50). You'll also note that the cell
striations are not as easily seen in myocardial cells compared to skeletal.
Smooth muscle (#7, scalp; #32, small intestine)
Smooth muscle bundles form the arrector pili muscle which
attaches to the hair shaft. It's hard to find the muscle attaching directly to the hair
apparatus. Hints: muscle is lighter pink than surrounding almost "red" connective tissue;
the nuclei in smooth muscle are usually staggered and oriented in rows rather than
the disorder of connective tissue fibroblast nuclei; the arrector pili muscle
is usually seen near the sebaceous gland of the hair.
In small intestine (#32) look for the smooth muscle layers in
outer layers of the cross section of the intestine. Note that the two outer layers run
in two different orientations.
You'll learn more of these bundles in Dr. Eigenbrodt's G.I.
System lectures and labs. Again notice the more orderly appearance of smooth muscle
compared to the underlying connective tissue. Be thinking ahead as to why
intestine has these layers of muscle and why they are oriented as they are.