|Lab: Sheep Heart
Observation: External Anatomy
Most heart diagrams show the left atrium and ventricle on the right side of the diagram. Imagine the heart in the body of a person facing you. The left side of their heart is on their left, but since you are facing them, it is on your right.
|2. Turn the heart so that the right
side is on your right, as if it were in your body. Examine the flaps of
darker tissue on the top of the heart. These ear-like flaps are called auricles.
Find the large opening at the top of the heart next to the right auricle.
This is the opening to the superior vena cava, which brings blood
from the top half of the body to the right atrium (the atria are
the top chambers in the heart). Stick a probe down this vessel. You should
feel it open into the right atrium. A little down and to the left of the
superior vena cava there is another blood vessel opening. Insert your probe
into this; it should also lead into the right atrium. This is the inferior
vena cava, which brings blood from the lower tissues. You can also see
another blood vessel next to the left auricle. This is a pulmonary vein
that brings blood from the lungs into the left atrium.
Superior vena cava _______
Insert probe to the right atrium ________
3. Sticking straight up from the center of the heart is the largest blood vessel you will see. This is the aorta, which takes oxygenated blood from the left ventricle to the rest of the body (the ventricles are the lower chambers of the heart). The aorta branches into more than one artery right after it leaves the heart, so it may have more than one opening on your heart specimen. Look carefully at the openings and you should be able to see that they are connected to each other.
Pulmonary artery _______
1. Insert your dissecting scissors or scalpel into the superior vena cava and make an incision down through the wall of the right atrium and ventricle, as shown by the dotted line in the external heart picture. Pull the two sides apart and look for three flaps of membrane. These membranes form the tricuspid valve between the right atrium and the right ventricle. The membranes are connected to flaps of muscle called the papillary muscles by tendons called the chordae tendinae or "heartstrings." This valve allows blood to enter the ventricle from the atrium, but prevents backflow from the ventricle into the atrium.
tricuspid valve ________
Insert probe into the pulmonary artery _______
|3. Insert your dissecting scissors
or scalpel into the left auricle at the base of the aorta and make an incision
down through the wall of the left atrium and ventricle, as shown by the
dotted line in the external heart picture. Locate the mitral valve
(or bicuspid valve) between the left atrium and ventricle. This will have
two flaps of membrane connected to papillary muscles by tendons.
Mitral valve ______