THE HEART

[Pages:35]THE HEART

Dr. AYISHA QURESHI Professor

MBBS, MPhil

Why does the heart develop so early?

Location of the Heart:

Heart walls are composed of 3 distinct layers:

1. ENDOCARDIUM (inner): thin layer of endothelium that lines the entire circulatory system (endo means "within").

2. MYOCARDIUM (middle): composed of cardiac muscle that forms the bulk of heart wall (myo means "muscle").

3. EPICARDIUM (outer): thin external membrane covering the heart (epi means "on").

The Pericardium & the Pericardial Sac:

The heart is enclosed in a double-walled, membranous pericardial sac. The sac consists of two layers--a tough, fibrous outer covering and a secretory inner lining.

The outer fibrous covering of the sac attaches to the connective tissue partition that separates the lungs. This attachment anchors the heart so that it remains properly positioned within the chest.

The secretory lining secretes the Pericardial Fluid, which provides lubrication to prevent friction between the pericardial layers as they glide over each other with every beat of the heart.

Pericarditis, an inflammation of the pericardial sac that results in a painful friction rub between the two pericardial layers, occurs occasionally because of viral or bacterial infection.

SOME KEY POINTS ABOUT HEART

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