Download The BROKEN HEART

STRAIGHT FROM THE HEART
A Heart Dissection Lab
BACKGROUND: The heart’s main function is to keep
blood circulating throughout the body. Every cell of the
body needs glucose and oxygen and needs to get rid of
carbon dioxide, excess water, and other wastes. In
mammals the heart is four-chambered. There are two
upper chambers known as auricles or atria and two lower
chambers known as the ventricles. The two upper
chambers are very thin and the two lower chambers are highly muscular. You will find that one of
the ventricles is much thicker than the other. There are many known diseases and disorders that
affect the heart and circulatory system. Today there are procedures that can open narrow
arteries, bypass diseased arteries in the heart itself, and repair congenital defects of the heart.
One defect that babies can be born with is PDA – patent ductus arteriosis.
Babies with this
defect are sometimes called “blue babies” because they take on a slightly bluish color due to the
mixing of oxygenated and deoxygenated blood. In this lab you will simulate repairing PDA and also
doing bypass surgery.
PDA: In a fetus, the ductus arteriosus diverts blood from the pulmonary artery to the aorta,
bypassing the lungs which are undeveloped and not ready to exchange oxygen and carbon dioxide.
During fetal development, the embryo is getting oxygen from the mother’s blood. When the baby is
born, the great increase in oxygen caused the ductus to constrict and shut off so that the blood
can now go through the pulmonary artery to the lungs. If the ductus arteriosus, connecting the
pulmonary artery and the aorta, does not close after birth, then the blood will not get oxygenated
efficiently. PDA is detected when there are abnormal heart sounds (murmurs) and cyanosis (bluish
color).
Coronary Bypass: Coronary arteries are the vessels that bring nutrients and oxygen to the heart
muscle, itself. If these arteries become blocked with cholesterol plaque, then the flow of blood is
hindered and a heart attack can result. One way of dealing with this problem is to remove a vein
from the patient’s leg and using it to “bypass” the blocked part of the coronary artery. A triple
bypass is done when three blocked areas are “bypassed” with three little pieces of vein.
MATERIALS:
Veal heart
Plastic tubing
disposable gloves
Dissecting tray
dissecting equipment
PROCEDURE:
1. Put your heart in the tray so that the ventral surface of the heart is facing you. To do this
find the floppy looking atria and put these at the top. Feel the bottom of the heart on
both sides. One side will feel thicker (left ventricle). Position the heart so that the left
ventricle is on your right and the atria are sort of away from you. You will be able to see
the large coronary artery that is separating the heart into two sections.
2. Try to find all of the vessels in your heart – use your fingers and your probe to determine
where these vessels go.
3. With your scalpel, cut your heart along dotted lines A and B. Cut through all the muscle –
but leave some of the bottom uncut. Keep the two incisions separate. Notice that one wall
is thicker than the other.
4. Looking inside the right and left ventricles, note the cords that go from the bottom of each
ventricle to the atrium above it. These cords help with valve function. Notice the septum
that divides the two ventricles.
5. Put your finger in the right ventricle and try to move it into the right atrium and then into
the vena cava.
6. Now, use your finger again to fine the pulmonary artery that leaves the right ventricle.
7. Put your finger into the left ventricle. Find the large blood vessel that leaves the left
ventricle. Put your finger into this vessel – the aorta.
PDA SURGERY:
1.
Find the thin bridge of ligament between the pulmonary artery and the aorta. You might
need to cut away some of the fat. Put a pin into this area. This is the area that a surgeon
would stitch closed.
CORONARY BYPASS SURGERY:
1. Make a small hole near the base of the aorta and put one end of the plastic tubing in the
hole.
2. Find the coronary artery on the surface of the left ventricle. Make a hole in the artery so
that you can put the other end of the tube into the opening you have made.
The Broken Heart
Name______________________________
QUESTIONS:
1.
Fill in the blanks below to show the path of blood from the vena cava to the aorta. Each
space should have a names of a structure or a substance.
The vena cava brings blood loaded with CO2 to the ______________________, which
delivers the blood to the ___________________. This chamber pumps the CO 2 loaded
blood through the _______________________ to the _____________________ where
the blood gives up its CO2 and takes in __________________. The blood then returns to
the heart through the ___________________ and enters the ____________________.
This chamber delivers blood into the ______________________ which pumps it through
____________________ to all parts of the body.
2.
Make a diagram showing the flow of blood in a baby with PDA.
3.
Why is patent ductus a dangerous condition?
this question.
4.
Which side of the heart should be called the “low O 2” side? Why?
Refer to your illustration as you answer
5. Where does the blood in the pulmonary vein come from?
6. Name and describe three circulatory disorders not mentioned in this lab.
7. Why is the muscle of the left ventricle so much thicker?