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Laboratory 14 Heart Anatomy Objectives: •
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Describe the position of the heart in the thoracic cavity. Decribe the coverings of the heart. Describe the layers of the pericardium and their function. Identify and describe the function of the primary internal structures of the heart, including chambers, septa, valves, papillary muscles, chordae tendineae, and venous and arterial openings. Describe blood flow through the heart naming all chambers and valves passed. Identify the major blood vessels entering and leaving the heart and classify them as either an artery or a vein and as containing either oxygen-­‐rich or oxygen-­‐poor blood. Describe the systemic and pulmonary circuits and discuss the functions of each. State which blood vessel type carries oxygen-­‐rich blood and which type carries oxygen-­‐poor blood in each circuit. 1. Heart Overview: The human heart is a four-­‐chambered, muscular pump that functions to move blood through the body through our system of blood vessels. The heart is a fist-­‐sized organ located midline in the pericardial cavity in between the lungs, immediately dorsal to the sternum. The heart is composed primarily of a cardiac muscle tissue. The heart has four chambers. Two chambers receive blood from the body, the atria. The other two chambers, the ventricles, receive blood from the atria and pump it to the rest of the body. The right atrium receive blood from most of the body, and pumps that blood into the right ventricle. The right ventricle then pumps the blood out through the pulmonary arteries into pulmonary circulation. The left atrium receives blood returning from the lungs. Blood flows from the veins coming into the right atrium to the right ventricle out of the heart through the pulmonary arteries to the lungs. Blood returns to the heart from the pulmonary veins into the left atrium to the left ventricle out to the rest of the body. Heart valves are important in maintaining this one-­‐directional flow through the heart. There are two atrioventricular (AV) valves, which are between the atria and the ventricles. The atrioventricular valve on the right side of the heart is the tricuspid valve. Between the left atrium and ventricle is the mitral, or bicuspic, valve. The two semilunar valves, which are in the arteries leaving the heart, are the aortic valve and the pulmonary valve. The heart is composed of three layers of tissue: the epicardium, the connective tissue outer layer; the myocardium, the largest layer composed of cardiac muscle; and the endocardium, the thin, inner layer of epithelial tissue that is continuous with the endothelial lining of the blood vessels. The heart is enclosed in a two-­‐layer protective layer called the pericardium. The pericardium has an outer fibrous pericardium and an inner serous pericardium. Between the two layers of pericardium is a fluid-­‐filled space, the pericardial cavity. The epicardium is part of the serous pericardium. 41 42 •
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Locate the position of the human heart on the models. Review anatomical right and left. Review the characteristic of cardiac muscle tissue and how it compares to skeletal muscle tissue. Use the textbook and the heart models to locate the features of the heart on the list provided by your instructor. 2. Blood Supply to the Heart: Although the heart is filled with blood, the blood supply to the myocardium is through coronary arteries with the blood returning through coronary veins. The two major coronary arteries, the right and left coronary arteries, originate from the left side of the heart at the base of the aorta and run near the surface of the heart. The right coronary artery supplies the right atrium, the posterior right ventricle and some of the posterior left ventricle. The marginal artery, braches off of the right coronary artery on the side of the heart and supplies the lateral right ventricle. The left coronary artery bifurcates into the circumflex artery, which travels in the left atrio-­‐ventricular groove, and the anterior interventricular artery, which parallels the anterior interventricular sulcus. The circumflex artery encircles the heart providing blood flow to the left atrium and the posterior left ventricle. The anterior interventricular artery supplies blood to the interventricular septum as well as the anterior ventricles. Three veins drain the myocardium: the great cardiac vein, the middle cardiac vein, and the small cardiac vein. These three vessels merge into the flattened coronary sinus which drains into the right atrium. 43 3. Sheep Heart (or Pig Pluck) Dissection: (Note: some classes may dissect a pig heart from a pluck. Instructions are similar and instructor will highlight the differences in lab) Sheep hearts are similar anatomically to human hearts. We will dissect sheep hearts to get a better understanding of human heart anatomy. A couple of cameras will be provided, but feel free to use your cell phone cameras. The assignment is to photo-­‐document a proper sheep heart dissection showing all features you are responsible for knowing on a sheep heart. Images should be uploaded into Powerpoint, Google Presentations, or some other appropriate software and correctly labeled. One collection of labeled photos will be submitted for each table of students. 1. Obtain a preserved sheep heart. Rinse it thoroughly in water to remove some of the preservative. a. For pig pluck, rinse really well, until most of the blood is removed from both the lung and heart. b. Remove the heart from the trachea, esophagus, and lungs. Note the relative position to those organs. 2. Excess fat is often present at the base of the heart surrounding the major blood vessels. This fat can be dissected away for easier viewing. 3. If the both pericardial membranes are intact, then remove the serous pericardium. Near the apex, using a scalpel, remove a small portion of the viscerial pericardium. Note its thickness and position relative to the heart. 4. One the exterior of the heart, identify these structures: a. Apex b. Base c. Right atrium d. Right ventricle e. Left atrium f. Left ventricle g. two auricles h. Interventricular groove (anterior or posterior) i. Atrioventricular sulcus. 5. On the exterior of the heart, identity these blood vessels: a. Superior vena cava b. Inferior vena cava c. Pulmonary arteries d. Aorta e. Pulmonary trunk. 6. Cut along the side of the heart, bisecting it into anterior and posterior halve. Begin with a cut through the vena cava into the right atrium to expose the tricuspid valve. Note the opening of the coronary sinus in between the inferior vena cava and the right AV valve. 7. Continue to cut through the right AV valve to the apex. Expose the right ventricle and locate the papillary muscles and chordae tendinae. Note the interventricular and interatrial septa, and the pulmonary semilunar valve. 44 8. Continue the cut up through the left ventricle and atrium. Note the mitral (or bicuspid) valve, the aortic semilunar valve, the papillary muscles and chordae tendinae on the left side. If possible, find the two openings to the coronary arteries. 4. Identification List: * = know on sheep (or pig) heart also
Heart:
Layers
Fibrous Pericardium (covering,
cannot be seen on models)
Pericardial cavity
Epicardium (also called serous
pericardium)
Myocardium
Endocardium
Orientation:
Apex*
Base*
Right and Left*
External Structures:
Auricles*
Anterior interventricular groove*
Posterior interventricular groove*
Atrioventricular sulcus*
Major Coronary Vessels:
Left coronary artery
Anterior interventricular artery
Circumflex artery
Right coronary artery
Posterior interventricular artery
Great cardiac vein
Coronary sinus
Vessels Connected Directly to Heart Chambers:
Superior vena cava*
Inferior vena cava*
Pulmonary arteries*
Aorta (ascending, arch, descending)*
Brachiocephalic artery/trunk
Left common carotid artery
Left subclavian artery
Pulmonary trunk*
Pulmonary arteries
Internal Structures
Atria (left & right)*
Interatrial septum*
Fossa ovalis
Atrioventricular Valves:
Tricuspid valve*
Bicuspid (mitral) valve*
Ventricles (left & right) *
Papillary muscles*
Chorda tendonae*
Interventricular septum*
Semilunar Valves
Pulmonary semilunar valve*
Aortic semilunar valve*
Histological features
Cardiac myocyte
Intercalated discs
Nucleus
5. Submitting the assignment: •
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The assignment is to photo-­‐document a proper heart dissection with features you are responsible for knowing labeled. Images should be uploaded into Powerpoint, Google Presentations, or some other appropriate software and correctly labeled. Alternatively, tables can make use hand written labels and pins to label the hearts prior to taking photographs. One collection of labeled photos will be submitted for each table of students. 45 Attribution of images used in this document: Figure 1A.van Brussel, Ties. (2010). [Anatomy of the human heart]. Wikimedia Commons. Retrieved July 16, 2012 from http://commons.wikimedia.org/wiki/File:Anatomy_Heart_English_Tiesworks.jpg Figure 1B. Lynch, Patrick J. (2006). [Heart anterior normal anatomy]. Wikimedia Commons. Retrieved July 16, 2012 from http://commons.wikimedia.org/wiki/File:Heart_anterior_normal_anatomy.jpg. Figure 2. Lynch, Patrick J. (2007). [Coronary arteries]. Wikimedia Commons. Retrieved July 16, 2012 from http://commons.wikimedia.org/wiki/File:Coronary.pdf.
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