Wall of the Heart

The wall of the heart is composed of three distinct layers: an outer epicardium, a middle myocardium, and an inner endocardium (fig. 15.5).

The epicardium (ep"i-kar'de-um), which corresponds to the visceral pericardium, is protective. It is a serous membrane that consists of connective tissue cov ered by epithelium, and it includes blood capillaries, lymph capillaries, and nerve fibers. The deeper portion of the epicardium often contains fat, particularly along the paths of coronary arteries and cardiac veins that provide blood flow through the myocardium.

The middle layer, or myocardium (mi"o-kar'de-um), is thick and largely consists of the cardiac muscle tissue that pumps blood out of the heart chambers. The muscle fibers are arranged in planes, separated by connective tissues that are richly supplied with blood capillaries, lymph capillaries, and nerve fibers.

The inner layer, or endocardium (en"do-kar'de-um), consists of epithelium and connective tissue that contains many elastic and collagenous fibers. The endocardium also contains blood vessels and some specialized cardiac muscle fibers called Purkinje fibers,

Shier-Butler-Lewis: Human Anatomy and Physiology, Ninth Edition

IV. Transport

15. Cardiovascular System

© The McGraw-Hill Companies, 2001

Layer

Composition

Function

Epicardium (visceral pericardium)

Serous membrane of connective tissue covered with epithelium and including blood capillaries, lymph capillaries, and nerve fibers

Forms a protective outer covering; secretes serous fluid

Myocardium

Cardiac muscle tissue separated by connective tissues and including blood capillaries, lymph capillaries, and nerve fibers

Contracts to pump blood from the heart chambers

Endocardium

Membrane of epithelium and connective tissues, including elastic and collagenous fibers, blood vessels, and specialized muscle fibers

Forms a protective inner lining of the chambers and valves

Epicardium Myocardium Endocardium

Pericardial cavity

Parietal pericardium

Fibrous pericardium

Coronary blood vessel

Endocardium Myocardium

Epicardium (visceral pericardium)

Figure 15.5

The heart wall has three layers: an endocardium, a myocardium, and an epicardium.

Pericardial cavity

Parietal pericardium

Fibrous pericardium

Coronary blood vessel

Endocardium Myocardium

Epicardium (visceral pericardium)

Figure 15.5

The heart wall has three layers: an endocardium, a myocardium, and an epicardium.

described later in this chapter in the section titled "Cardiac Conduction System."

The endocardium lines all of the heart chambers and covers the structures, such as the heart valves, that project into them. This inner lining is also continuous with the inner lining of the blood vessels (endothelium) attached to the heart. Table 15.1 summarizes the characteristics of the three layers of the heart wall.

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Responses

  • Kasey
    What tissue is in the serosa of blood vessel?
    4 years ago
  • niklas
    What layer of the heart wall is continuous with the valves and blood vessells?
    4 years ago
  • atte
    What includes the epicardium, myocardium and endocardium?
    4 years ago
  • Lexie
    What part of the heart includes bllod capillaries, lymph cappilaries, nerve fibers and fat?
    4 years ago
  • Theodoric
    Where are the coronary vessels myocardium epicardium?
    2 years ago
  • alex ferguson
    Which layer of the vein wall contains nerve fibers?
    2 years ago
  • RODDY
    What is the function of the fibrous layer in the blood vessel?
    2 years ago
  • Katy
    Which heart wall corresponds to visceral pericardium?
    2 years ago
  • Ponto Roper
    Which wall of the heart is continuous with the lining of the vessel?
    1 year ago
  • Alicia
    Is the fat covering blood vessels in the myocardium?
    11 months ago
  • Sarah
    Which layer of heart contains nerve fiber?
    2 months ago

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