FETAL PIG II
Anatomy of the Cardiovascular System of the Fetal Pig
Introduction:
The cardiovascular system in the fetal pig is very similar
to the cardiovascular system in humans. In this lab
exercise we will be studying the anatomy of the fetal
pig’s heart and major blood vessels that carry blood to
the heart (vena cava) and away from the heart
(arteries).
Most of the blood vessels we will be observing are part
of the systemic circuit. The systemic circuit includes the
chambers of the heart and blood vessels that carry
blood to the body systems, except the lungs, and return
the blood to the heart.
As you work with the blood vessels there are several
things to remember:
The arteries should be filled with red latex and the
veins may be filled with blue latex.
Arterial walls are thicker than veins. The red latex
may be difficult to see within the major arteries.
Blood vessel diameter gets smaller as the blood vessel branches. The smaller the diameter, the more fragile
the blood vessel.
Blood vessels are most commonly named for the organs they serve or the area they travel through. For the
most part, each time the blood vessel branches it gets a new name.
Arteries and veins (and nerves) travel together through tissues. In many cases your blunt probe can be
passed through the organ or tissue along with the vessels to follow their course.
Proper dissection of blood vessels, requires the blunt probe to be passed under the blood vessel (until it
branches). As you gently break the connective tissue surrounding the blood vessels take care not to
lift/stretch the blood vessels because they are easily broken.
Dissection Exercise: Fetal Pig II, page
1
Activity 1: Dissection of Blood Vessels above the Diaphragm
Lab Safety: All students are required to
wear goggles and nonlatex gloves while
working with their specimens.
Biohazard: All students are required to
wash their hands, tools and bench with soap
and water after they have completed the
dissection activities. Razor blades are always
disposed of in the biohazard container.
Dissection Tools: Dissection tray, Blunt probe,
Sharp probe, Scissors, Razor
Specimen: Fetal Pig (1 specimen per pair of
students, continuation of dissection)
In order to dissect out the blood vessels, review the anatomy of the fetal pig heart and the human heart by using
the diagrams. You should have removed a small portion of the pericardial sac and thymus that covers the base
of the heart in order to see the great vessels that leave the heart. As you view the heart, you can view the
pulmonary trunk easily along the surface whereas, the aorta and anterior (superior) vena cava are attached
posteriorly. Keep in mind veins return blood to the atria, and arteries carry blood away from the heart due to the
contractions of the ventricles.
Procedure:
1. Before lab, draw a few diagrams with labels of the blood vessels as indicated by bold-faced type within this
procedure. Practice identifying your blood vessels on the photographs provided here or the Fetal Pig II
Photoalbum Online.
2. Assemble all of the dissection tools, specimen and put on your goggles and nonlatex gloves.
Dissection Exercise: Fetal Pig II, page 115
3. If you have not removed a small portion of the
pericardial sac and the thymus gland that sits
atop the base (superior/wide portion of the
heart). Use your scissors and forceps to
complete this in order to identify the atria,
ventricles, apex, coronary blood vessels and
pulmonary trunk of your specimen.
a. The coronary blood vessels lie on the
surface of the heart and are used to
identify the right and left sides of the
heart. These blood vessels bring blood
to/from the myocardium (cardiac tissue)
because as the blood passes through the
heart, it is traveling too fast for exchange to occur with
the tissues of the heart.
b. The pulmonary trunk carries deoxygenated blood from
the right ventricle to the lungs. It is commonly a large
white vessel that is seen on the ventral side of the fetal
pig between the atria. (See photograph on previous
page)
4. Identify the aorta (arch) dorsal to the pulmonary trunk. The
aorta carries oxygenated blood away from the heart’s left
ventricle to other body organs and forms an inverted ‘J’ as it
travels posteriorly along the dorsal wall through both the
thoracic and abdominal cavities. As blood vessels branch off
of the aorta, they are named for the organs the arteries carry
blood to. The aorta has the thickest vessel walls of all the
blood vessels. The aorta commonly appears whitish because
the wall is so thick that the red latex is not visible through the
wall.
5.
Bringing blood back to the heart is the anterior (humans
superior) vena cava and posterior vena cava. The anterior
vena cava brings deoxygenated blood back from the head
and upper body while the posterior vena cava brings deoxygenated blood back from the posterior organs
and hind limbs. The veins
that merge to form the
anterior vena cava lay
along the same pathway
as the arteries that branch
from the aorta. While the
posterior vena cava lay
on the ventral aspect of
the aorta as it travels
through the thoracic and
abdominal cavities. Both
vena cava have extremely
thin walls and are easily
broken with the blunt
probe.
Dissection Exercise: Fetal Pig II, page 116
6. The first branch off the aorta is the
brachiocephalic artery. The name
identifies the locations it serves—brachioserves the brachium and cephalic serves
the head. The brachiocephalic artery is
usually short and branches into three other
arteries: the right subclavian (passes subunder the clavicle-clavicle), and the right
and left carotid arteries (carry blood to the
head).
7. Follow the right and left carotid arteries
into the neck region by gently breaking the
connective tissue that holds the neck region
organs in place. Follow these arteries until
they branch.
8. The right subclavian continues toward the
brachium. Follow the right subclavian into
the tissues of the arm. Your blunt probe
should pass through the tissues allowing
you to cut through the tissues atop the
probe. Once the blood vessel reaches the brachium, it gets a new name—the right brachial artery.
9. The left subclavian artery is dorsal to the brachiocephalic off of the aortic arch. Gently push the heart to
the right as you find the left subclavian and follow it as it continues on as the left brachial artery into the
arm of the specimen.
10. Practice identifying the blood vessels from
the heart into the neck, both arms, and
posteriorly to the diaphragm.
11. Record your dissection steps and
observations in your lab notebook.
Dissection Exercise: Fetal Pig II, page 117
Activity 2: Dissection of the Blood Vessels Posterior to the Diaphragm
Procedure:
1. Before lab, read through the procedure and draw diagrams of the blood vessels you will be finding and label
these. Practice identifying the blood vessels on the photographs here and in your Fetal Pig Photoalbum
Online.
2. The aorta passes through both the abdominal and thoracic cavity with the posterior vena running top its
ventral surface. To identify the abdominal aorta, keep in mind the aorta should be filled with red latex so it
will be cylindrical, while the vena cava is commonly (filled with blue latex) collapsed lying atop the aorta as
you view your specimen or off to one side. The easiest place to begin is with the kidneys. Your kidneys
should be free of the peritoneum and as you observe the dorsal aspect of the kidneys, you should find the
renal artery that connects the kidney to the medial abdominal aorta. (Renal refers to the kidney, so the renal
artery brings oxygenated blood from the aorta to the kidney).
3. At about the level of the renal artery, you may see the
very tiny (diameter) gonadal arteries. The gonadal
arteries are also called the spermatic artery in the
male and ovarian artery in the female.
4. Moving cranially along the abdominal aorta from the
renal artery, find the anterior (superior) mesenteric
artery. It will be necessary to move the abdominal
organs to the side to find this branch. The anterior
mesenteric artery supplies blood to the pancreas and
small intestine.
5. The next branch moving cranially is the celiac artery
which branches further supplying blood to the liver
duodenum, spleen and stomach.
6. The blood vessels posterior to the renal arteries are
closely associated with the urinary and reproductive
system organs. Use care to keep these structures
intact as you continue working.
Dissection Exercise: Fetal Pig II, page 118
7. The abdominal aorta terminates in four branches: the right and left external iliac, and the right and left
internal iliac arteries. The internal iliac arteries are also the umbilical arteries in a fetus. It may be easier to
follow the umbilical/internal iliac arteries to the abdominal aorta OR follow the abdominal aorta from the renal
arteries toward the internal iliac arteries. As you follow the internal iliac arteries, preserve your reproductive
structures and ureters (the tube that carries urine from the kidneys to the bladder) for future dissections.
8. The external iliac arteries continue (and branch, but we will not be naming all of the branches) into the leg.
Once the external iliac enters into the hind limb, it is called the femoral artery. Branching off the femoral is a
smaller deep femoral artery.
9. Practice identifying the blood vessels once they have been dissected out, you should be able to lift each
blood vessel up with the probe (between branches) and identify it from the diaphragm to the hind limb.
10. Complete your documentation and answer the associated questions in your lab notebook.
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Dissection Exercise: Fetal Pig II, page 120