Heart. Endocardium, heart valves. Myocardium: typical and atypical muscles, conducting system. Epicardial and pericardial structure

Heart. Endocardium, heart valves. Myocardium: typical and atypical muscles, conducting system. Epicardial and pericardial structure.

Heart

The heart is a muscular organ in most animals that pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide to the lungs.In humans, the heart is approximately the size of a closed fist and is located between the lungs, in the middle compartment of the chest.

Heart function

Your heart’s main function is to move blood throughout your body.

Your heart also:

•Controls the rhythm and speed of your heart rate.

•Maintains your blood pressure.

What is a heart valve?

Your heart is a muscle that pumps blood throughout your body. Heart valves are parts of your heart that act like doors. They open and close to let blood flow from one area of your heart to another. They help ensure that blood moves at the right time and in the correct direction. As the valves open and close, they create two sounds, which are your heartbeat.

The four valves of the heart are:

•Aortic valve.

•Mitral valve.

•Pulmonary valve (or pulmonic valve).

•Tricuspid valve.

The epicardium refers to the outermost protective layer of the heart. The epicardium is composed of mesothelium, a cell type that covers and protects most of the internal organs of the body as well as fat and connective tissue. The epicardium predominantly surrounds the heart and the roots of the coronary vessels emerging from it, including the aorta, the superior vena cava, and inferior vena cava. 

The other two layers surrounding the heart include the myocardium (i.e., the middle muscular layer that supports the pumping capabilities of the heart) and the endocardium, or the innermost layer.

Normal pericardium consists of an outer sac called fibrous pericardium and an inner one called serous pericardium. The two layers of serous pericardium: visceral and parietal are separated by the pericardial cavity, which contains 20 to 60 mL of the plasma ultrafiltrate. The pericardium acts as mechanical protection for the heart and big vessels, and a lubrication to reduce friction between the heart and the surrounding structures. A very important role in all aspects of pericardial functions is played by mesothelial cells. The mesothelial cells form a monolayer lining the serosal cavity and play an important role in antigen presentation, inflammation and tissue repair, coagulation and fibrinolysis. 

Cardiac muscle tissue, or myocardium, is a specialized type of muscle tissue that forms the heart. This muscle tissue, which contracts and releases involuntarily, is responsible for keeping the heart pumping blood around the body.

The human body contains three different kinds of muscle tissue: skeletal, smooth, and cardiac. Only cardiac muscle tissue, comprising cells called myocytes, is present in the heart.