Failure of the Conduction System of the Heart-Commotio Cordis

Failure of the Conduction System of the Heart

The sinuatrial node is the spontaneous source of the cardiac impulse. The atrioventricular node is responsible for picking up the cardiac impulse from the atria. The atrioventricular bundle is the only route by which the cardiac impulse can spread from the atria to the ventricles. Failure of the bundle to conduct the normal impulses results in alteration in the rhythmic contraction of the ventricles (arrhythmias) or, if complete bundle block occurs, complete dissociation between the atria and ventricular rates of contraction. The common cause of defective conduction through the bundle or its branches is atherosclerosis of the coronary arteries, which results in a diminished blood supply to the conducting system

Commotio Cordis

This condition results in ventricular fibrillation and sudden death and is caused by a blunt nonpenetrating blow to the anterior chest wall over the heart. It occurs most commonly in the young and adolescents and is often sports-related. The sudden blow is frequently produced by a baseball, baseball bat, lacrosse ball, or fist or elbow. The common incidence in the young is most likely due to the compliant chest wall due to the flexible ribs and costal cartilages and the thin undeveloped chest muscles. Apparently, timing of the blow relative to the cardiac cycle is critical; ventricular fibrillation is most likely to occur if the blow occurs during the upstroke of the T wave of the electrical activity of the cardiac muscle.

  

Diseases of Blood Vessels-Disease of the Lymphatic System

Diseases of Blood Vessels

Diseases of blood vessels are common. The surface anatomy of the main arteries, especially those of the limbs.
 The collateral circulation of most large arteries should be understood, and a distinction should be made between anatomic end arteries and functional end arteries. All large arteries that cross over a joint are liable to be kinked during movements of the joint. However, the distal flow of blood is not interrupted because an adequate anastomosis is usually between branches of the artery that arise both proximal and distal to the joint. The alternative blood channels, which dilate under these circumstances, form the collateral circulation. Knowledge of the existence and position of such a circulation may be of vital importance should it be necessary to tie off a large artery that has been damaged by trauma or disease. Coronary arteries are functional end arteries, and if they become blocked by disease (coronary arterial occlusion is common), the cardiac muscle normally supplied by that artery will receive insufficient blood and undergo necrosis. Blockage of a large coronary artery results in the death of the patient

Disease of the Lymphatic System

The lymphatic system is often de-emphasized by anatomists on the grounds that it is difficult to see on a cadaver.
 However, it is of vital importance to medical personnel, since lymph nodes may swell as the result of metastases, or primary tumor. For this reason, the lymphatic drainage of all major organs of the body, including the skin, should be known. A patient may complain of a swelling produced by the enlargement of a lymph node. A physician must know the areas of the body that drain lymph to a particular node if he or she is to be able to find the primary site of the disease. Often, the patient ignores the primary disease, which may be a small, painless cancer of the skin. Conversely, the patient may complain of a painful ulcer of the tongue, for example, and the physician must know the lymph drainage of the tongue to be able to determine whether the disease has spread beyond the limits of the tongue