Fetal
Pig Dissection
General Tips
Tools --
the most useful dissection tool is a blunt probe. It will separate tissues
easily along natural cleavage lines, without damaging the structures being
studied. If cutting is necessary, a scissors is the best choice, because it will
only cut between the blades. Razor blades and scalpels are almost totally
unnecessary, and of course are a danger both to the specimen and the people
doing the dissection. In fact, in our lab, we no longer distribute razor blades
or scalpels with the dissection kits. A scalpel can be used to nick the skin to
provide access for a scissors. Once that is done, there is really no need to
ever again use any instrument more dangerous than a scissors. In order to
dispense with the razor blade and scalpel, it probably helps to have small,
sharp, fine pointed scissors.
Speed & Caution
-- Look at the
pictures and read directions carefully. The FPDG (Fetal Pig Dissection Guide)
is deliberately designed so that the text describing a structure can be read
without turning away from the page with the illustration of the structure. Once
you have read the directions, ask questions if any seem obvious. Otherwise, go
to it! Occasional mistakes are inevitable, and part of the learning process. If
you make a mistake, you can always ask to see other specimens for better
examples of structures. In the case of paired structures, you may want to look
on the other side of your specimen.
Look at other specimens
-- Even if your
dissection goes well, look at other pigs regularly. No two pigs will look
exactly alike. This is partly due to differences in dissection technique, but
mostly due to natural variation in the structures of two different animals of
the same species. This is the way animals are in the real world! Surgeons can't
count on the renal arteries always having exactly the same structure, so they do
diagnostic tests before attempting a kidney transplant. Different fetal pigs are
the same; small differences in structures are very common, large differences are
not unusual. In addition, if you are tested by way of practical tests, you will
need to be able to recognize a structure in whatever animal is used on the test.
Once you have seen a structure in several animals, you should have no difficulty
in recognizing a good example of it in any specimen.
Anomalies -- minor internal malformations are very common in
fetal pigs, as is the case with most mammals. Actually it would probably be more
accurate to call them developmental variations instead of malformations, since
most of these variations would be perfectly normal functionally. The most common
developmental variations are in the blood vessels, especially the veins.
Splitting of the abdominal vena cava is a common example. It arises from the
failure of the cardinal veins to completely fuse.
Human/Pig
Comparisons
Similarity
to human structure
-- Pigs are mammals. Consequently, all of the major structures found in humans
are present in the fetal pig. With proper directions, they can all be readily
found, especially with large, full term fetal pig specimens. There are a some
differences in structural details, mostly relatively minor in nature. Some
examples are given below.
Muscles
In almost every case,
fetal pigs have the same muscles as humans, with some small variations in the
size and location of some muscles related to the fact that pigs are quadrupedal
and humans are bipedal. For example, the major chest and abdominal muscles found
in humans are present in the pig. There are some differences in the location of
chest muscles that attach to the shoulder girdle. In the hind limb, the pig has
the same muscles as humans in the major thigh muscle groups: quadriceps femoris
and the hamstrings. In the hip, however, there are some differences in the
gluteal muscles.
Pig
and Dissection Humor
What
follows are some puns, jokes and riddles that relate to things in a fetal pig
dissection lab: science, medicine, anatomy and pigs.
Some
of these jokes are real 'groaner' puns, so if you can't stand such jokes, please
close your eyes!
Pigs