Name:___________________
KEY
Per:____ Date:____________
Sheep Heart Dissection
Learning Goal/Question: You will observe the outside and inside of a sheep heart to locate and label
the parts of a heart, including blood vessels, chambers and valves. You will also study the direction
of blood flow through the heart, including oxygenated and deoxygenated blood.
Collect Info: Your heart is a muscle that can push about five liters of liquid through your body each
minute. You heart squeezes or contracts 70 to 100 times a minute and relaxes for only about half a
second between contractions. When the heart contracts the right side sends deoxygenated blood
(blood low in oxygen and high in carbon dioxide) to your lungs. The left side of your heart sends
oxygenated blood (blood high in oxygen and low in carbon dioxide) to the body. The muscle on the
left side of the heart is much thicker than the right side of the heart because it has to pump blood
out of the heart with enough force to reach all the parts of your body. You heart has valves
separating each atrium and ventricle. The function of these valves is to prevent backflow of blood in
the heart. They keep blood flowing in one direction from the atrium to the ventricle.
You have blood vessels that carry blood to and from the heart. The vessels that carry blood
away from the heart are called arteries. Most arteries carry oxygenated blood away from the heart
and to the body. The vessels that carry blood toward the heart are called veins. Most veins carry
deoxygenated blood from the body cells toward the heart. Blood pressure is caused by the force in
which your heart contracts and pushes blood against your artery walls. The big push of blood causes
the arteries to push out and produce a pulse. When you measure your heart rate, you are feeling for
and counting that surge of blood, or “pulse”, each time your heart contracts.
Sheep have a four-chambered heart, just like humans. By studying the anatomy of a sheep's
heart, you can learn about how your own heart pumps blood through your body and keeps you alive!
Label the parts of the heart. This will help you during the heart dissection.
superior vena cava
right atrium
from body
aorta
pulmonary artery
pulmonary vein
valves
left atrium
valves
inferior vena cava
from body
right ventricle
left ventricle
Discussion:
1. As blood passes through the pulmonary artery, it is pumped to the lungs. If blood leaves the
right side of the heart deoxygenated and returns to the left side oxygenated, what gas has
been added to the blood?
Oxygen
a. Through what organ system must the blood pass through in order to change in this way?
Respiratory system (lungs)
2. Red blood cells carry oxygenated blood to all the tissues/cells in your body. If a person has
sickle cell anemia, red blood cells do not work properly. How would this affect a person’s
body(tissues/cells)?
Red blood cells carry oxygen, so if they are not working properly this will reduce/lower
the amount of oxygen carried/distributed to your cells/tissues. This will affect your cells
ability to release energy through cellular respiration.
3. When you exercise, your cells need more oxygen so they can do cellular respiration to release
more energy. Why does your heart rate and breathing increase when you exercise?
Your breathing will increase to take in more oxygen that your cells need for respiration.
Your heart rate will increase to pump blood faster through the body to deliver the
oxygen your cells need for respiration.
4. What are the two functions of the valves in the heart?
Your valves prevent the backflow of blood in the heart (and veins). Your vavles keep
blood flowing in one direction.
a. If a person is diagnosed with a heart murmur, it could mean that one of the valves in the
heart is not functioning properly. How will this affect the heart?
If the valve is not functioning properly, there will be some backflow of blood in the
heart.
5. Explain why the muscle of the left ventricle is thicker than the muscle of the right ventricle.
The muscle on the left side of the heart is much thicker than the right side of the
heart because it has to pump blood out of the heart with enough force to reach all the
parts of your body.
6. What is blood pressure?
Blood pressure is the force of blood pushing against the artery walls when the heart
contracts. OR Blood pressure is caused by the force in which your heart contracts
and pushes blood against your artery walls.
a. If your heart has to contract harder to force the blood out into the arteries, how will
that affect blood pressure?
Your blood pressure will increase or be higher if your heart has to contract harder.