Chapter 11 The Cardiovascular System

The Cardiovascular System  A closed system of the heart and blood vessels  The heart pumps blood  Blood vessels circulate the blood to all parts of the body  Function  Deliver oxygen and nutrients to the body  Remove carbon dioxide and other waste products

The Cardiovascular System  Structures  Heart  Pumps the blood through the body  Blood Vessels  Arteries carry blood with oxygen away from the heart (away)  Veins carry deoxygenated blood back to the heart (visit)  Capillaries exchange the gases

The Heart  About the size of a fist and weighs less than a pound  Anterior to the vertebral column and posterior to the sternum  The base is a broad, flat surface on the top  The apex is the bottom that points towards the left hip  The internal partition that divides the heart longitudinally is called the septum

The Heart: Four Chambers  Right and left side act as separate pumps  Atria: the receiving chambers  Right atrium  Blood returns from the body to the heart via the superior (above diaphragm) vena cava and inferior (below diaphragm) vena cava  Left atrium  Blood returns to the heart from the lungs to the heart via the four pulmonary veins

The Heart: Chambers  Ventricles: discharging chambers or actual pumps  Together they make up most of the volume of the heart  Their walls are more muscular than the atria  Right ventricle  Pumps blood into the pulmonary arteries and into the lungs where gas exchange occurs  Left ventricle  Pumps blood into the aorta, the largest artery in the body  Walls are three times thicker than the right ventricle

The Heart: Major Arteries and Veins  Superior Vena Cava and Inferior Vena Cava  Blood returns from the body into the right atrium  Pulmonary arteries  Carries deoxygenated blood to the lungs  Pulmonary veins (four)  Carries oxygenated blood to the heart  Aorta  Blood leaves left ventricle to the body

Heart Valves  Blood flows in one direction: from atria to ventricles and out the great arteries leaving the superior aspect of the heart  Four valves enforce blood flow in one direction and prevent backflow in response to differences in blood pressure

Heart Valves  Atrioventricular (AV) valves  Prevent backflow into the atria when the ventricles are contracting  Right AV valve is the tricuspid valve  Left AV valve is the mitral (bicuspid) valve  Attached to each AV valve flap are tiny white collagen cords called chordae tendineae, “heart strings”, which anchor the cusps to the muscles  Semilunar (SL) valves  Prevent backflow into the associated ventricles when the ventricles relax  Pulmonary semilunar valve  Aortic semilunar valve

Pathway of Blood through the Heart  Two side-by-side pumps that serve different circuits  Pulmonary circuit  The pulmonary arteries carry blood from the heart to the lungs for gas exchange and the pulmonary veins carry the blood back to the heart  Only arteries that carry deoxygenated blood and only veins that carry oxygenated blood only in the body  Systemic circuit  The arteries that carry blood from the heart to the capillary beds in body tissues and back to the heart via veins

Deoxygenated blood comes in from the top of the body through the superior vena cava and the lower parts of the body though the inferior vena cava into the right atrium. The tricuspid valve closes.

The right atrium contracts and the tricuspid valve opens, forcing the blood down into the right ventricle.

The right ventricle contracts forcing the deoxygenated blood through the pulmonary valve and into the right and left pulmonary arteries. This starts the pulmonary circuit. PULMONARY ARTERIES ARE THE ONLY ARTERIES THAT CARRY DEOXYGENATED BLOOD.

In the lungs, the carbon dioxide in the blood diffuses into the alveoli and the oxygen diffuses into the blood. This is called gas exchange.

Oxygenated blood from the lungs enters the heart through four pulmonary veins into the left atrium. The (bicuspid) mitral valve is closed to keep the blood from going into the left ventricle. PULMONARY VEINS ARE THE ONLY VEINS THAT CARRY OXYGENATED BLOOD.

The left atrium contracts. forcing the oxygenated blood through the mitral valve into the left ventricle. The mitral valve closes again. This keeps the oxygenated blood from moving back up into the left atrium.

Oxygenated blood is forced through the aortic semilunar valve into the aorta to be carried to the rest of the body through the systemic circuit.

Oxygenated blood is carried to all body cells where oxygen diffuses into the cells and carbon dioxide diffuses into the blood in the capillaries Blood carrying carbon dioxide then returns to the heart via the veins. And the cycle begins again

Blood Flow Heart Pulmonary Heart Systemic Start here