Procedure B Dissection Of A Sheep Heart

1. Obtain a preserved sheep heart. Rinse it in water thoroughly to remove as much of the preservative as possible. Also run water into the large blood vessels to force any blood clots out of the heart chambers.

2. Place the heart in a dissecting tray with its ventral side up (fig. 41.4) and proceed as follows:

Figure 41.2 Label this posterior view of the human heart.

Figure 41.2 Label this posterior view of the human heart.

Sheep Heart Posterior Anatomy

a. Although the relatively thick pericardial sac probably is missing, look for traces of this membrane around the origins of the large blood vessels.

b. Locate the visceral pericardium that appears as a thin, transparent layer on the surface of the heart. Use a scalpel to remove a portion of this layer and expose the myocardium beneath. Also note the abundance of fat along the paths of various blood vessels. This adipose tissue occurs in the loose connective tissue that underlies the visceral pericardium.

c. Identify the following:

right atrium right ventricle left atrium left ventricle atrioventricular sulcus anterior interventricular sulcus d. Carefully remove the fat from the anterior interventricular sulcus, and expose the blood vessels that pass along this groove. They include a branch of the left coronary artery (anterior interventricular artery) and a cardiac vein.

3. Examine the dorsal surface of the heart (fig. 41.5)

and proceed as follows:

a. Identify the atrioventricular sulcus and the posterior interventricular sulcus.

b. Locate the stumps of two relatively thin-walled veins that enter the right atrium. Demonstrate this connection by passing a slender probe through them. The upper vessel is the superior vena cava, and the lower one is the inferior vena cava.

4. Open the right atrium. To do this, follow these steps:

a. Insert a blade of the scissors into the superior vena cava, and cut downward through the atrial wall (fig. 41.5).

b. Open the chamber, locate the tricuspid valve, and examine its cusps.

c. Also locate the opening to the coronary sinus between the valve and the inferior vena cava.

d. Run some water through the tricuspid valve to fill the chamber of the right ventricle.

e. Gently squeeze the ventricles, and watch the cusps of the valve as the water moves up against them.

5. Open the right ventricle as follows:

Figure 41.3 Label this anterior view of a coronal section of the human heart.

- Brachiocephalic artery

- Left common carotid artery

- Left subclavian artery

Brachiocephalic veins

Figure 41.3 Label this anterior view of a coronal section of the human heart.

Brachiocephalic veins

- Brachiocephalic artery

- Left common carotid artery

- Left subclavian artery

Right pulmonary veins

(chamber)

Right pulmonary veins

Sheep Heart Labeled Epicardium

Epicardium

Myocardium

Endocardium

Epicardium

Myocardium

Endocardium

(chamber)

(chamber)

(chamber)

a. Continue cutting downward through the tricuspid valve and the right ventricular wall until you reach the apex of the heart.

b. Locate the chordae tendineae and the papillary muscles.

c. Find the opening to the pulmonary trunk, and use the scissors to cut upward through the wall of the right ventricle. Follow the pulmonary trunk until you have exposed the pulmonary valve.

d. Examine the valve and its cusps.

6. Open the left side of the heart. To do this, follow these steps:

a. Insert the blade of the scissors through the wall of the left atrium and cut downward to the apex of the heart.

Open the left atrium, and locate the four openings of the pulmonary veins. Pass a slender probe through each opening, and locate the stump of its vessel.

Examine the bicuspid valve and its cusps. Also examine the left ventricle, and compare the thickness of its wall with that of the right ventricle.

7. Locate the aorta which leads away from the left ventricle and proceed as follows:

a. Compare the thickness of the aortic wall with that of a pulmonary artery.

b. Use scissors to cut along the length of the aorta to expose the aortic valve at its base.

c. Examine the cusps of the valve, and locate the openings of the coronary arteries just distal to them.

8. As a review, locate and identify the stumps of each of the major blood vessels associated with the heart.

9. Discard or save the specimen as directed by the laboratory instructor.

10. Complete Part B of the laboratory report.

Web Quest

Trace blood flow through an animated heart at various rates. Identify heart structures and take an animated tour of the heart. Search these at http://www.mhhe.com/ biosci/abio/martinlmwq.mhtml

Figure 41.4 Ventral side of sheep heart.

Superior vena cava Brachiocephalic artery Right atrium

Right ventricle

Superior vena cava Brachiocephalic artery Right atrium

Right ventricle

Sheep Heart Superior Cava

Aorta

Ligamentum arteriosum

Pulmonary trunk Left atrium

Atrioventricular sulcus

Anterior interventricular sulcus

Left ventricle

Apex

Aorta

Ligamentum arteriosum

Pulmonary trunk Left atrium

Atrioventricular sulcus

Anterior interventricular sulcus

Left ventricle

Apex

Figure 41.5 Dorsal side of sheep heart. To open the right atrium, insert a blade of the scissors into the superior (anterior in sheep) vena cava and cut downward.

Aorta Pulmonary trunk

Left atrium Inferior vena cava

Left ventricle

Figure 41.5 Dorsal side of sheep heart. To open the right atrium, insert a blade of the scissors into the superior (anterior in sheep) vena cava and cut downward.

Aorta Pulmonary trunk

Left atrium Inferior vena cava

Left ventricle

Anterior Atrioventricular Sulcus

Superior vena cava

Right atrium

Atrioventricular sulcus

Right ventricle

Posterior interventricular sulcus

Superior vena cava

Right atrium

Atrioventricular sulcus

Right ventricle

Posterior interventricular sulcus

Essentials of Human Physiology

Essentials of Human Physiology

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Responses

  • mat brownlock
    How to identify dorsal sides during heart dissection?
    5 years ago
  • lyyli
    Where is the anterior sulcus on a sheep heart?
    4 years ago
  • Breann Downey
    What is The membrane around a human heart?
    3 years ago

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