Introduction

 The heart pumps blood  Blood vessels provide the conduits within which blood circulates to all body tissues  Main function: ◦ Transportation

The main organ of the circulatory system

 Location and Size  Coverings and Wall  Chambers  Valves Page 329 in book

 The relative size and weight of the heart give a few hints to the incredible strength the heart has  Size: ◦ approx. size of fist  Shape: ◦ Hollow, Cone-shaped  Weight: ◦ Less than a pound

 Apex points toward the left hip and rests on the diaphragm ◦ Approx. where the left intercoastal space is  Where you would place a stethoscope to hear the heart beats  Base – broader posterosuperior aspect, from where the great vessels of the body emerge, points toward the right shoulder and lies beneath the 2 nd rib

 Pericardium: ◦ double sac of serous membrane  The thin visceral pericardium, or epicardium tightly hugs the external surface of the heart and part of the heart wall  A lot of connective tissue  There is a fibrous layer helps protect the heart and anchors it to surrounding structures such as the diaphragm and the sternum  A slippery lubricating fluid (serious fluid) is produced by the pericardial membranes ◦ The fluid allows the heart to beat easily in a relatively frictionless environment as the pericardial layers slide smoothly across each other  Myocardium: ◦ Consists of think bundles of cardiac muscle twisted around and actually contracts  Endocardium: ◦ Thin, glistening sheet of endothelium that lines the heart chambers

 Two atria  Two ventricles  Each of these is lined with endocardium, which helps blood flow smoothly through the heart  The superior atria are typically the receiving chambers ◦ They are not important in the actual pumping activity ◦ Blood flows into the atria under low pressure from the veins of the body and then continues to fill the ventricles  The inferior, thick-walled ventricles are the discharging chambers, or actual pumps of the heart  Video Video

 Read information on page

Cardiac Circulation/ Operation

 Circulation Song Circulation Song  Pg 333

 1. Once the deoxygenated red blood cell (RBC) returns to the heart, it enters either through the superior vana cava or the inferior vena cava. The superior vena cava returns deoxygenated blood from the upper part of the body to the heart. The inferior vena cava returns deoxygenated blood from the lower part of the body to the heart. These large veins lead into the right atrium.  2. The RBC passes through the tricuspid valve into the right ventricle.  3. The RBC is then pumped through the pulmonary valve into the pulmonary artery and on to the lungs. There the RBC gives off carbon dioxide and picks up oxygen.  4. The RBC returns to the heart through a pulmonary vein, enters the left atrium, passes through the mitral valve, and flows into the left ventricle.  5. The left ventricle pumps the fully oxygenated RBC through the aortic valve, into the aorta, the body's main artery, and out to the body.  6. From the aorta, the RBC flows into one of the many arteries of the body, through the arterioles, and then to the capillaries, where the RBC will deliver oxygen and nutrients to the cells and remove wastes and carbon dioxide. Next it moves through the venules, veins, and on to the vena cava in a deoxygenated state, and returns to the heart, only to begin its repetitive journey once again. This whole process has taken approximately 20 seconds!  That single RBC will travel about 950 miles (more than 1500 kilometers) in its brief 4- month lifetime!