Difference Between Myocardium and Pericardium

The main difference between myocardium and pericardium is that the myocardium is the muscular layer of the heart made up of heart muscles whereas the pericardium is the fibrous encase of the heart made up of connective tissue. Furthermore, the myocardium is responsible for heart contractions while pericardium is responsible for the protection of the heart.

Epicardium, myocardium, and endocardium are the three layers of the wall of the heart while pericardium is the membrane that surrounds the heart.

Key Areas Covered

1. What is Myocardium
     – Definition, Structure, Function
2. What is Pericardium
     – Definition, Structure, Function
3. What are the Similarities Between Myocardium and Pericardium
     – Outline of Common Features
4. What is the Difference Between Myocardium and Pericardium
     – Comparison of Key Differences

Key Terms

Cardiac Contraction, Heart Wall, Fibrous Pericardium, Myocardium, Pericardial Cavity, Pericardium, Serous Pericardium

What is Myocardium

Myocardium is the middle layer of the wall of the heart, made up of the heart muscle fibers. It is the thickest layer of the heart wall. The thickness of the myocardium varies in different parts of the heart. The wall of the left ventricle comprises the thickest myocardium layer since the left ventricle is responsible for pumping blood throughout the body. The pressure produced by each chamber depends on the thickness of the myocardium.

Figure 1: Heart Wall

The contraction of heart muscles is under the control of the peripheral nervous system. Heart contractions are involuntary muscular movements. Cardiac conduction refers to the rate at which the heart conducts electrical impulses. It is facilitated by the specialized muscle fibers in the myocardium. The fiber bundles such as atrioventricular bundle and Purkinje fibers conduct the impulses from the center of the heart to the ventricles, triggering the contraction of the ventricles.

What is Pericardium

Pericardium is the fibrous encase that covers the heart. It consists of two layers of connective tissue. Serous pericardium, pericardial cavity, and fibrous pericardium are the three layers of the pericardium.

• Serous pericardium – The inner/visceral layer of the pericardium. Two layers of the serous pericardium are the outer parietal layer, which lines the internal surface of the fibrous pericardium, and the internal visceral layer, also known as the epicardium.
• Fibrous pericardium – The outer/parietal layer of the pericardium is made up of tough connective tissue. It prevents the overfilling of the heart.
• Pericardial cavity – The space between two layers, filled with serous fluid. Pericardial cavity aids in the pumping action of the heart.
  

  Figure 2: Pericardium

The main function of the pericardium is to provide protection against infections while lubricating the heart. Also, it fixes the heart to the mediastinum.

Similarities Between Myocardium and Pericardium

• Myocardium and pericardium are two layers, involved in the formation of the structure of the heart.
• Both help in the pumping of blood.

Difference Between Myocardium and Pericardium

Definition

Myocardium refers to the muscular tissue of the heart, which is made up of heart muscles while pericardium refers to the membrane enclosing the heart, consisting of an outer fibrous layer and an inner double layer of serous membrane.

Location

Further, the myocardium is the middle layer of the heart wall while the pericardium is the outermost layer of the heart.

Made up of

Also, myocardium is made up of heart muscles while pericardium is made up of connective tissue.

Number of Layers

Moreover, myocardium makes up a single layer while pericardium makes up two layers.

Function

Regarding the function, the myocardium is responsible for heart contractions while the pericardium is responsible for the protection of the heart while preventing overfilling.

Conclusion

Myocardium is the middle, muscular layer of the heart made up of heart muscles. On the other hand, pericardium is the outermost, membranous structure of the heart, which protects the heart and prevent the overfilling. The main difference between myocardium and pericardium is their structure and function.

Reference:

1. Bailey, Regina. “The Layers of the Heart Wall.” ThoughtCo, ThoughtCo, Available Here
2. “The Pericardium.” TeachMeAnatomy, 10 Mar. 2018, Available Here

Image Courtesy:

1. “Blausen 0470 HeartWall” By BruceBlaus. Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia   
2. “Serous Membrane” By Connexions (CC BY 3.0) via Commons Wikimedia