Chapter 11- Part 1 The Cardiovascular System

The Cardiovascular System  A closed system of the heart and blood vessels  The heart pumps blood  Blood vessels allow blood to circulate to all parts of the body  The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

The Heart  Location  Within the bony thorax and is flanked on each side by the lungs  Shape and Size  Pointed apex directed toward left hip and rests on the diaphragm  The broader base (posterior/superior aspect of heart) points towards the right shoulder and lies beneath the 2 nd rib  About the size of your fist

The Heart: Coverings  The heart is covered by a double sac of serous membrane, the pericardium. The pericardium contains two layers: 1.Visceral Pericardium (Epicardium) – Layer next to heart; Tightly hugs the exterior surface of the heart; Actually forms part of the heart wall 2.Parietal Pericardium - Outside layer; Fibrous layer that helps protect the heart and anchors it to surrounding structures (diaphragm and sternum)

The Heart: Coverings  Serous Fluid - Fills the space between the layers of the pericardium  Slippery, lubricating fluid  Allows the heart to beat easily in a relatively frictionless environment as the pericardial layers slide smoothly across each another  Pericarditis – Inflammation of the pericardium; Often results in the decrease in the amount of serous fluid  Painful adhesions result that interfere with heart movements (layers stick to each other)

The Three Layers of the Heart Wall 1.Epicardium  Outside layer  This layer is the visceral pericardium already described  Connective tissue layer 2.Myocardium  Middle layer  Mostly cardiac muscle; layer that actually contracts 3.Endocardium  Inner layer  Thin glistening sheet of endothelium that lines the heart chambers

The Heart: Chambers  Right and left side act as separate pumps  Four chambers  Atria - Receiving chambers Not important in the pumping activity of the heart Right atrium and left atrium  Ventricles - Discharging chamber  Actual pumps of the heart  Thick walled  Right ventricle and left ventricle

The Heart: Chambers  The heart is somewhat twisted:  Anterior surface of the heart is formed mostly by the right ventricle  The apex of the heart is formed by the left ventricle

The Heart: Chambers Septums that divide the heart longitudinally:  Interventricular Septum – Divides and separates the two ventricles from each other  Interatrial Septum - Divides and separates the two atria from each other

The Heart: Chambers  The heart functions as a double pump:  Right Side: Pulmonary circuit pump  Left Side: Supply all body tissues

The Heart: Associated Great Vessels  Aorta - Leaves left ventricle  Pulmonary Arteries - Leave right ventricle  Vena Cava - Enters right atrium  Pulmonary Veins (four) - Enter left atrium

Blood Circulation 1.The superior and inferior vena cava deliver oxygen poor blood from the veins of the body to the right atria 2.Right ventricle 3.Pulmonary arteries to the lungs to get oxygen and drop off carbon dioxide 4.Oxygen rich blood is returned to the left side of the heart through the four pulmonary veins 5.Left atria 6.Left ventricle 7.Oxygen rich blood is pumped out of the heart into the aorta, from which the systemic arteries branch to supply essentially all body tissues

Blood Circulation 1.Pulmonary Circulation – Circulation from the right side of the heart to the lungs and back to the left side of the heart It’s only function is to carry blood to the lungs for gas exchange and then return it to the heart 2.Systemic Circulation – Circulation from the left side of the heart to the body tissues and back to the right side of the heart It supplies oxygen- and nutrient-rich blood to all body organs

Blood Circulation Figure 11.3

Thickness of the Ventricles  Left Ventricle  Is the systemic pump that pumps blood over a much longer pathway  Its walls are substantially thicker than those of the right ventricle  More powerful pump than the left ventricle  Right Ventricle  Not as powerful or as thick as the left ventricle

The Heart: Valves  Allow blood to flow in only one direction  Four valves total (two AV valves and two semilunar valves)  Atrioventricular (AV) Valves – Located between the atria and ventricles  Left AV Valve – Called the bicuspid valve or the mitral valve (contains two cusps or flaps)  Right AV Valve – Called the tricuspid valve (contains three cusps or flaps)

The Heart: Valves  Semilunar Valves – Located between the ventricle and artery  Pulmonary Semilunar Valve – Right side of heart (contains three cusps)  Aortic Semilunar Valve – Left side of heart (contains three cusps)

The Heart: Valves  Valves open (flaps hang limply) as blood is pumped through  Close to prevent backflow  As the ventricles contract, the pressure causes the flaps to be forced upward, closing the valves

The Heart: Valves  The flaps of the AV valves are held in a closed position by the chordae tendineae  Tiny white cords  Anchor the cusps to the walls of the ventricles, so that they don’t blow upward into the atria (like an umbrella being turned inside out by a gusty wind)

The Heart: Valves  Each set of valves operates at a different time -  The AV Valves:  Open during heart relaxation  Closed when the ventricles are contracting  Semilunar Valves:  Open (forced open) when the ventricles contract  Closed during heart relaxation  The “lub-dup” sound of the heart is from the opening and closing of the valves.

Faulty Valves  The heart can function with “leaky” valves as long as the damage is not too great.  However, severely deformed valves can seriously hamper cardiac function.  If blood backflows too much, the heart repumps the same blood.  If the flap stiffens, the heart’s workload increases, and ultimately the heart weakens and may fail.

Faulty Valves  Treatment: A faulty valve can be replaced with a synthetic valve or a valve taken from a pig heart.