ENDOCARDIUM: MAIN FUNCTIONS AND CHARACTERISTICS - ANATOMY AND PHYSIOLOGY - 2024

The endocardium is the innermost layer of the many layers that line the heart. This thin sheet covers all the compartments and all the valves of the heart.

The endocardium is made up of a simple epithelium called the endothelium. This is supported by internal and external subendothelial layers of dense or loose connective tissue, respectively.

The endothelium forms a continuous sheet with the endothelial lining of the blood vessels.

Because the endocardium lines the internal structures of the heart, including atria and ventricles, it is always in contact with the bloodstream.

The thickness of the endocardium varies throughout the different structures of the heart, the endocardium of the ventricles being thinner than that of the atria.

The 3 layers of the endocardium

1- Endothelium

It is a simple squamous epithelium, formed by specialized cells that line the interior of the circulatory system, where they are in direct contact with the blood.

2- Fibroelastic fabric

It is a thin layer made up of a mixture of collagen fibers, elastic tissue, and some smooth muscle. This tissue is usually thicker in the atria than in the ventricles.

3- Subendocardial connective tissue

It is the deepest layer of the endocardium. It is made up of connective tissue and Purkinje fibers.

Connective tissue helps the endocardium join the myocardium, and Purkinje fibers help conduct electricity through the heart muscle.

Features

Even though the endocardium is a very thin layer of tissue, it serves three important functions for the cardiovascular system.

First, the endocardium provides a smooth surface for the inside of the heart. This smooth surface allows blood to flow freely throughout the tissues.

Without this layer, blood components could adhere to the walls of the heart and cause tissue damage or even blockages.

Second, the endocardium plays a critical role in the heartbeat by containing Purkinje fibers.

Purkinje fibers in the endocardium help transmit electrical signals throughout the heart. This electricity helps the heart muscles contract - it's what makes the heart beat.

Third, the endocardium forms additional folds around the heart valves (atrio-ventricular and semi-lunar), which help the valves to be stronger and work better.

In summary, the heart is a very powerful organ in the cardiovascular system and the endocardium is one of the layers that make up the heart, which is why it is an element of great importance.

References

1. Brutsaert, D. (1989). The Endocardium. Annual Review of Physiology, 51, 263-273.
2. Clark, R. (2005). Anatomy and Physiology: Understanding the Human Body. Illustrated Edition. Jones & Bartlett Learning.
3. Harris, I. & Black, B. (2010). Development of the Endocardium. Pediatric Cardiology, 31, 391-399.
4. Henrikson, R. & Mazurkiewicz, J. (1997). Histology, Volume 518. National Medical Series. The National Medical Series for Independent Study. Illustrated Edition. Lippincott Williams & Wilkins
5. Iaizzo, P. (2005). Handbook of cardiac anatomy, physiology and devices. Humana Press Inc.
6. Katz, A. (2011). Physiology of the heart. 5 ^th Lippincott Williams & Wilkins, a Wolters Kluwer business.