3. List the three tissue layers of the heart. Give a brief description of the ro

Question

3. List the three tissue layers of the heart. Give a brief description of the role of each. Describe the pathology of pericarditis and pericardial tamponade. Explain what is meant by the ‘cardiac cycle’ with reference to only the ventricles. List its two basic parts, tell how long each lasts (typically), and what happened (ie. direction of blood flow) during each part.

4. List the factors that affect vascular resistance. Which of these is manipulated by the brain to maintain blood pressures in a normal range? Explain why blood pressure and velocity drop as we move away from the heart. Relate this to the change in total cross sectional area as we move away from the heart.

Explanation / Answer

Three tissue layers of the heart:

            1. the epicardium (external layer),

            2. the myocardium (middle layer) and

            3. the endocardium (inner layer).

1. The Epicardium: This is the outermost layer of the heart wall. It is made up of a thin layer of connective tissue and fats. It offers the protection to the heart.

2. The myocardium: This is the middle layer of the heart wall. It is the thicker most layer of the heart wall comprised of cardiac muscle cells, cardiomycets. These muscle cells brings out continuous rhythmic contraction. Because of this continuous contraction it need uninterrupted blood supply which is accomplished by coronary arteries.

3. Endocardium: THis is the innermost layer of the heart wall made up of endothellial cells. Endocarium plays an important role in regulation of contractility and provides smooth surface for blood collection and pumping.

Pathology of pericarditis and pericardial tamponade

Pericarditis refers to inflammation of the pericardium. In this condition there is accumulation of the fluid in the pericardial cavity, the condition is precisely known as pericardial effusion. The fluid accumulated can vary as serous, lymph or pus etc. The condition becomes more serious when the accumulated fluid exert pressure on the heart which interferes the normal functioning of the heart. If this not treated then it leads to formation of critical condition known as pericardial tamponade.

Cardiac Cycle

The cardiac cycle refers to a complete a single heartbeat. It has two parts as diastole and systole with a little pause between them. On an average, healthy adult person counts 70 beats per minute. Hence a single cardiac cycle takes around 0.8 seconds. Of this 0.1 is arterial systole, 0.3 seconds ventricular systole followed by arterial and ventricular diastole together 0.8 seconds.

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