HEART

HEART

• The human heart is a muscular organ that pumps blood around the body.
• The constant circulation supplies oxygen and nutrients to all organs and tissues, as well as carrying waste away.
• The heart has two chambers,divided by a muscular septum.
• One-way blood flow between the upper atrium and the lower ventricle is controlled by the valves.
• The heart is located in the left side of the mediastinum.

HEART CONSISTS 3 LAYERS:

1. The epicardium is the outermost layer of the heart.
2. The myocardium is the middle layer and is the actual contracting muscle of the heart.
3. The endocardium  is the inner most layer and lines the inner chambers and heart valves.

HEART CONSISTS 4 CHAMBERS:

1. The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava.
2. The right ventricle receives blood from the right atrium and pumps it to the lungs via the pulmonary artery.
3. The left atrium receives oxygenated blood from the lungs via 4 pulmonary veins.
4. The left ventricle is the largest and most muscular chamber, it receives oxygenated blood from the lungs via the left atrium and pumps blood into the systemic circulation via the aorta.

HEART SOUNDS:

1. The first heart sound (s1) is heard as the atrioventricular valves close and is heard loudesr at the apex of the heart.
2. The second heart sound (s2) is heard when the semi lunar valves close and is heard loudest at the base of the heart.
3. A third heart sound (s3) may be heard if ventricular wall compliance is decreased and structures in the ventricular wall vibrate; this can occur in conditions such as heart failure or valvular regurgitation. however, a third heart sound may be normal in individuals younger than 30 years.
4. A fourth heart sound (s4) may be heard on atrial systole if resistance to ventricular filling is present; this is an abnormal finding, and the causes include cardiac hypertrophy, disease, or injury to ventricular wall.

HEART RATE:

• The faster the rate, the less time the heart has for filling, and the cardiac output decreases.
• An increase in heart rate increases oxygen consumption.
• The normal sinus heart rate is 60 to 100 beats/minute.
• Sinus tachycardia is a rate more than 100 beats/minute.
• Sinus bradycardia is a rate less than 60 beats/minute.