Administration



Sheep Heart Dissection

The laboratory sheet

Objective:

In this exercise, you will:

1. Examine, identify, and learn the functions of the exterior and interior anatomy of the heart

2. Trace the pathway of blood through the heart, pulmonary and systemic systems

3. Follow the events in the heart as it pumps

Vocabulary:

atrium

ventricle

coronary artery

vein

artery

Websites to have open to lend a helping hand:

National Geographic - the human body - heart () - this site will help with finding out the functions of all the parts and to see what a human heart would look like.

ZeroBiology Sheep Heart Dissection video () - a good video that shows what the parts actually look like in the heart

GWC Maricopa () - This site is good for labeling the interior and exterior of the heart

Home Science Tools () - this site is where these directions came from. You can click on the images for a much larger and clearer picture.

NOVA Map of the Human Heart () - this one is great at showing the flow of blood through the heart. it also does a good job labeling some of the structures.

Procedures:

As you move your way through this laboratory, make sure to label the heart on your data page and fill in the functions and descriptions of the parts that you are seeing.

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.

1. Identify the right and left sides of the heart. Look closely and on one side you will see a diagonal line of blood vessels that divide the heart. The half that includes all of the apex (pointed end) of the heart is the left side. Confirm this by squeezing each half of the heart. The left half will feel much firmer and more muscular than the right side. (The left side of the heart is stronger because it has to pump blood to the whole body. The right side only pumps blood to the lungs.)

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.

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.

4. Behind and to the left of the aorta there is another large vessel. This is the pulmonary artery which takes blood from the right ventricle to the lungs.

Dissection: Internal Anatomy

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.

2. Insert your probe into the pulmonary artery and see it come through to the right ventricle. Make an incision down through this artery and look inside it for three small membranous pockets. These form the pulmonary semilunar valve which prevents blood from flowing back into the right ventricle.

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.

4. Insert a probe into the aorta and observe where it connects to the left ventricle. Make an incision up through the aorta and examine the inside carefully for three small membranous pockets. These form the aortic semilunar valve which prevents blood from flowing back into the left ventricle.

Blood Flow

Using the National Geographic website and the Nova Map of the Human Heart interactive, trace the flow of blood through the heart picture. Use a blue marker for deoxygenated blood and a red marker for oxygenated blood.

Pumping Action of the Heart

1. Blood enters the top two chambers of the heart. Because they are made of muscle, they are able to squeeze together or contract. When this happens, blood is pumped to the two bottom chambers which are relaxed. These events are shown in Figure 4. Note that certain valves in Figure 4 are open while other valves are closed. Complete the first column of Table 2 on your Data Sheet.

2. Once blood fills the two bottom chambers they contract. Blood is then pumped out of the heart into the rest of the body. These events are shown in Figure 5. Note which valves are open or closed in Figure 5. Complete the second column of Table 2.

Data:

You shall record your data on the data sheet given with this, or on your own paper.

Analysis questions:

1. What is the job of the coronary artery?

2. Blood is pumped from the heart to the body through the aorta.

a. Which chamber does this job?

b. Does this blood have more oxygen or more carbon dioxide?

c. Which valves are open during this process?

3. Blood is pumped from the heart to the lungs through the pulmonary artery.

a. Which chamber does this job?

b. Does this blood have more oxygen or more carbon dioxide?

c. Which valves are open during this process?

4.Trace a drop of blood through the heart by putting these heart chambers, valves and external places in proper order: left atrium, aortic valve, pulmonary valve, right atrium, right ventricle, left ventricle, bicuspid valve (mitral valve), tricuspid valve, lungs, and body. Start with the Right atrium.

Conclusion:

Explain how the anatomy of the heart helps keep it efficient. Think about the blood oxygen levels and where the blood is going and tie that to the number of chambers. Also discuss the reasons for difference in the thickness of the ventricle chamber walls.

Error:

Don't forget to mention if anything went slightly different than the laboratory wanted it to.

Sheep Heart Dissection

Partners: Date: ___________________

Computer Guru_____________________________ Period __________________

Scribe ______________________________________

Surgeon ____________________________________

Don't forget to write up your own laboratory report. The data sheet will be only attached to one persons report, so record in your data section who the lucky person was that got to keep it.

Data:

Table 1: Anatomy of the Heart

|Structure |Function |Description |

|Aorta | | |

| | | |

|Pulmonary Artery | | |

| | | |

|Pulmonary Vein | | |

| | | |

|Coronary Arteries | | |

| | | |

|Superior Vena Cava | | |

| | | |

|Inferior Vena Cava | | |

| | | |

|Left Atrium | | |

| | | |

|Right Atrium | | |

| | | |

|Left Ventricle | | |

| | | |

|Right Ventricle | | |

| | | |

|Pulmonary Valve (semilunar | | |

|valve) | | |

|Aortic Valve (semilunar | | |

|valve) | | |

|Bicuspid (mitral) Valve | | |

| | | |

|Tricuspid Valve | | |

| | | |

Table 2: The opening and closing of parts of the heart

| |Blood entering ventricles |Blood leaving ventricles |

|The atria relaxed or contracted? | | |

|The ventricles relaxed or contracted? | | |

|Semilunar valves open or closed? | | |

|Bicuspid valve opened or closed? | | |

|Tricuspid valve opened or closed? | | |

Heart Diagram:

Label the following heart diagram and use blue and red markers to show the direction of blood flow.

Credits: This laboratory report has elements taken from the following locations. What is not from there is from my mind.

National Geographic ()

Home Science Tools ())

Biology an everyday experience - Glencoe/McGraw Hill

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