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Chapter 17 Notes (Heart)
Basic Anatomy & Physiology II (BIO-118-51 )
Camden County College
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Bio - 118
Instructor: Dm itry S. Gem bitsky, Ph.
The Heart
Study Topics
- Describe the location and general features of the heart and the structure of pericardium.
- Identify the layers of the heart wall.
- Trace the flow of blood through the heart, identifying the major blood vessels, chambers, and heart valves.
- Describe the differences in the action potentials and twitch contractions of skeletal muscle fibers and cardiac muscle cells.
- Describe the components and functions of the conducting system of the heart.
- Identify the electrical events associate with a normal ECG.
Lecture Outline
I. Heart Anatomy
A. Size, Location, and Orientation 1. The heart is the size of a fist and weighs 250–300 grams. 2. The heart is found in mediastinum and two-thirds lies left of the midsternal line. 3. The base is directed toward the right shoulder and the apex points toward the left hip. B. Coverings of the Heart 1. The heart is enclosed in a doubled-walled sac called the pericardium. 2. Deep to pericardium is the serous pericardium. 3. The parietal pericardium lines the inside of the pericardium. 4. The visceral pericardium, or epicardium, covers the surface of the heart. C. Layers of the Heart Wall 1. The myocardium is composed mainly of cardiac muscle and forms the bulk of the heart. 2. The endocardium lines the chambers of the heart. D. Chambers and Associated Great Vessels 1. The right and left atria are the receiving chambers of the heart. 2. The right ventricle pumps blood into the pulmonary trunk; the left ventricle pumps blood into the aorta.
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E. Pathway of Blood Through the Heart 1. The right side of the heart pumps blood into the pulmonary circuit; the left side of the heart pumps blood into the systemic circuit. F. Coronary Circulation 1. The heart receives no nourishment from the blood as it passes through the chamber. 2. The coronary circulation provides the blood supply for the heart cells. 3. In a myocardial infarction, there is prolonged coronary blockage that leads to cell death. G. Heart Valves 1. The tricuspid and bicuspid valves prevent backflow into the atria when the ventricles contract. 2. When the heart is relaxed the AV valves are open, and when the heart contracts the AV valves close. 3. The aortic and pulmonary semilunar valves are found in the major arteries leaving the heart. They prevent backflow of blood into the ventricles. 4. When the heart is relaxed the semilunar valves are closed, and when the heart contracts the semilunar valves are open. H. The Blood Supply to the Heart 1. The coronary arteries. a. Right coronary artery. (i) The marginal artery. (ii) The posterior interventricular artery. b. Left coronary artery. (i) The circumflex artery. (ii) The anterior interventricular artery. 2. The coronary veins. a. The great and middle coronary veins. b. The coronary sinus.
II. Properties of Cardiac Muscle Fibers
A. Microscopic Anatomy 1. Cardiac muscle is striated and contraction occurs via the sliding filament mechanism. 2. The cells are short, fat, branched, and interconnected by intercalated discs. B. Mechanism and Events of Contraction 1. Some cardiac muscle cells are self-excitable. 2. The heart contracts as unit or not at all. 3. The heart’s absolute refractory period is longer than a skeletal muscle’s, preventing tetanic contractions. C. Energy Requirements 1. The heart relies exclusively on aerobic respiration for its energy demands. 2. Cardiac muscle is capable of switching nutrient pathways to use whatever nutrient supply is available.
Chapter 17 Notes (Heart)
Course: Basic Anatomy & Physiology II (BIO-118-51 )
University: Camden County College
