The Heart

The blood, heart, and blood vessels form the cardiovascular system. The lymph, lymph nodes, and lymph vessels form the lymphatic system. The cardiovascular system and lymphatic system collectively make up the circulatory system. The circulatory system transports nutrients, hormones, and gases; gets rid of wastes; and helps maintain a constant body temperature.

The central organ of the cardiovascular system is the heart, the muscular organ that pumps blood through a network of blood vessels. The heart beats more than 2.5 billion times in an average life span. Yet this organ is slightly larger than a fist. The heart lies within the thoracic (chest) cavity, behind the sternum (breastbone) and between the two lungs. A tough, saclike membrane called the pericardium surrounds the heart and secretes a fluid that reduces friction as the heart beats.

Notice in Figure 46-1 that a septum (wall) vertically divides the heart into two sides. The right side pumps blood to the lungs, and the left side pumps blood to the other parts of the body. Each side of the heart is divided into an upper and lower chamber. Each upper chamber is called an atrium, and each lower chamber is called a ventricle.

Pulmonary (right semilunar) valve

Tricuspid (right -

atrioventricular)

valve

Right ventricle

Pulmonary (right semilunar) valve

Tricuspid (right -

atrioventricular)

valve

Right ventricle

Aortic (left semilunar) valve

Left atrium

Mitral (left atrioventricular)

valve

Left ventricle

Right atrium

Septum

Sirens Sleep Solution

Sirens Sleep Solution

Discover How To Sleep In Peace And Harmony In A World Full Of Uncertainty And Dramatically Improve Your Quality Of Life Today! Finally You Can Fully Equip Yourself With These “Must Have” Tools For Achieving Peace And Calmness And Live A Life Of Comfort That You Deserve!

Get My Free Ebook


Post a comment