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Boundless Anatomy and Physiology
Physiology Textbooks Boundless Anatomy and Physiology
Physiology Textbooks
Physiology

Chapter 17

Cardiovascular System: The Heart

Book Version 29
By Boundless
Boundless Anatomy and Physiology
Physiology
by Boundless
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Section 1
The Heart
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Anatomy of the Heart

The heart is an organ responsible for pumping blood through the blood vessels using rhythmic contractions of cardiac muscle.

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Pericardium

The pericardium is a thick, membranous, fluid-filled sac which encloses, protects, and nourishes the heart.

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Layers of the Heart Walls

The heart wall is comprised of three layers: the outer epicardium, the middle myocardium, and the inner endocardium.

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Chambers of the Heart

The heart has four chambers. The two atria receive blood into the heart and the two ventricles pump blood into circulation.

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Great Vessels of the Heart

Great vessels are the major vessels which directly carry blood into or out of the heart.

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Myocardial Thickness and Function

The myocardium (cardiac muscle) is the thickest section of the heart wall and contains cardiomyocytes, the contractile cells of the heart.

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Fibrous Skeleton of the Heart

The cardiac skeleton, also known the heart's fibrous skeleton, consists of dense connective tissue in the heart that separates the atria from the ventricles.

Section 2
Circulation and Heart Valves
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Heart Circulation

Coronary circulation is the circulation of blood in the blood vessels of the heart.

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Operation of Atrioventricular Valves

The atrioventricular valves separate the atria from the ventricles and prevent backflow from the ventricles into the atria during systole.

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Operation of Semilunar Valves

The semilunar valves allow blood to be pumped into the major arteries, but prevent backflow of blood from the arteries into the ventricles.

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Systemic and Pulmonary Circulation

The cardiovascular system has two distinct circulatory paths, pulmonary circulation and systemic circulation.

Section 3
Cardiac Muscle Tissue
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Microscopic Anatomy

Cardiac muscle appears striated due to the presence of sarcomeres, the highly-organized basic functional unit of muscle tissue.

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Mechanism and Contraction Events of Cardiac Muscle Fibers

Cardiac muscle fibers undergo coordinated contraction via calcium-induced calcium release conducted through the intercalated discs.

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Energy Requirements

Cardiac cells contain numerous mitochondria, which enable continuous aerobic respiration and production of adenosine triphosphate (ATP) for cardiac function.

Section 4
Physiology of the Heart
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Electrical Events

Cardiac contraction is initiated in the excitable cells of the sinoatrial (SA) node by both spontaneous depolarization and sympathetic activity.

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Electrocardiogram and Correlation of ECG Waves with Systole

An electrocardiogram, or ECG, is a recording of the heart's electrical activity as a graph over a period of time.

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Heart Sounds

The two major heart sounds are "lub" (from the closure of AV valves) and "dub: (from the closure of aortic and pulmonary valves).

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Cardiac Cycle

The cardiac cycle describes the heart's phases of contraction and relaxation that drive blood flow throughout the body.

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Cardiac Output

Cardiac output (Q or CO) is the volume of blood pumped by the heart, in particular by the left or right ventricle, in one minute.

Section 5
Exercise and the Heart
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Effects of Exercise on the Heart

Aerobic exercise promotes cardiovascular health, while physical inactivity is associated with increased morbidity and mortality.

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Boundless Anatomy and Physiology by Boundless
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Chapter 16
Cardiovascular System: Blood
  • Overview of Blood
  • Red Blood Cells
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Chapter 17
Cardiovascular System: The Heart
  • The Heart
  • Circulation and Heart Valves
  • Cardiac Muscle Tissue
  • Physiology of the Heart
  • Exercise and the Heart
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Chapter 18
Cardiovascular System: Blood Vessels
  • Blood Vessel Structure and Function
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  • Physiology of Circulation
  • Systemic Blood Pressure
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