The space between the parietal and visceral pericardium is filled with serous fluid, which protects the heart from any kind of external jerk or shock.

During depolarisation, the impulses are carried from endocardium to epicardium.

Endocardial membrane of the heart is made up of simple squamous epithelium. It performs the function of protection carried out by the endothelial wall.

Endocardium provides protection to the valves and heart chambers.

Intercalated discs are responsible for syncytium formation. Cardiac syncytium is a network of cardiomyocytes connected to each other by intercalated discs that enable the rapid transmission of electrical impulses through the network, enabling the syncytium to act in a coordinated contraction of myocardium.

Myocardium is made up of cardiac cells, which function in autorhythmicity. Some cardiac muscle cells are self-excitable, allowing for rhythmic waves of contraction to adjacent cells throughout the heart.

This is not true. Cardiac cells are spindle-shaped.

Cardiac cells are constantly undergoing contractions and require more energy to perform their functions. Thus, cardiac cells have more mitochondria. In fact, mitochondria occupy 25% of cell space.

Endocardium serves as a kind of blood-heart barrier and thus, controlling the ionic composition of the extracellular fluid in which the cardiomyocytes bathe.

Cl^- ions are not required for the contraction of heart muscles.

Mediastinum is located at the level of thoracic vertebrae T5 to T8.

Cardiac tamponade is relieved by pericardiectomy. It is caused due to excess fluid in pericardial cavity.

Visceral pericardium is fused with epicardium. The epicardium layer is immediately outside of the heart muscle proper.

Fish's heart has two chambers. It has one atrium and one ventricle.

The protective covering around the heart is called pericardium.