What tissue is the heart wall mainly composed of?

Heart disease is very common in our daily life. Many people need to undergo heart bypass surgery or heart valve surgery when they have a heart attack. Although the success rate of heart surgery has become higher and higher in recent years, there are still some risks. If some people have heart problems, most of them need capsule surgery. So what tissue is the heart wall mainly composed of?

The heart wall is composed of the endocardium, epicardium and myocardium. Among them, the myocardium is the main component of the heart wall.

1. It is divided into two parts, the atrial muscle and the ventricular muscle, both of which are attached to the cardiac fiber skeleton. The muscle bundles of the two are not continuous and are connected by conduction bundles. Therefore, the atria and ventricles can contract separately.

2. The myocardium is arranged in layers, but the myocardial fibers in each layer are aligned with each other, and the muscle fibers in the same layer can also be aligned with each other.

3. The superficial myocardium is covered by the epicardium, and the deep myocardium is lined with the endocardium.

Atrial muscle:

The muscle bundles are grid-like, with pectinate muscles and are relatively thin. It consists of two layers, shallow and deep. The superficial layer runs horizontally around the left and right atria, the deep layer is loop-shaped or circular, and some of the surrounding fibers surround the auricle, the vena cava orifice, the pulmonary vein orifice, and the oval fossa. When the atria contract, these fibers act as a sphincter to prevent blood from flowing back.

Ventricular muscle:

Thicker. Can be divided into shallow. Three layers of medium depth.

Superficial muscle: It starts from the fiber ring, runs obliquely to the lower left, forms a cardiac vortex at the apical twist, and then turns into the deep layer to become the longitudinal deep muscle.

Middle muscle: It also originates from the annular fiber. The muscle fibers circulate around the left and right ventricles, with the left ventricle being more developed.

Deep muscle: attached to the fiber ring, muscle fibers run longitudinally, continuous with the papillary muscle and column.

Function: When the superficial circular muscle and deep longitudinal muscle contract, they can shorten the ventricle, while the middle circular muscle can shrink the ventricular cavity when contracting.

2. Because the ventricular muscle moves toward the bottom of the heart during contraction, it can squeeze blood into the large blood vessels. Some myocardial fibers are spirally shaped. Their combined force can cause the apex to rotate clockwise during contraction, causing the apex to push forward during contraction. Therefore, the apex beat can be felt on the surface of the body.

Epicardium: The visceral layer of the serous pericardium, composed of squamous epithelial cells and loose connective tissue. It mainly wraps around large blood vessels. The pericardial cavity is formed between the outer membrane and the parietal pericardium, which contains a small amount of fluid to reduce friction. Good for heart beat.

Endocardium: It is composed of endothelium and subendothelial layer. The endothelium is a single layer of squamous epithelium with a smooth surface, which is conducive to blood flow. The subendothelial layer is composed of connective tissue and is divided into two layers. The inner layer is dense connective tissue with a small amount of smooth muscle fibers. The outer layer is close to the myocardium, called the subendocardium, which is loose connective tissue and contains blood vessels and nerves. It has a nutritional function. In the ventricle and subendocardial layer, there are branches of the cardiac conduction system that have a conduction function. The endocardium also folds to form heart valves, which maintain the normal flow direction of blood when the heart contracts and relaxes.