CHAPTER 11 The Cardiovascular System

Introduction The cardiovascular system is much more than just the heart. It also includes blood vessels. The major function of the cardiovascular system is transportation. Using blood as the transport vehicle, the system carries oxygen, nutrients, cell wastes, hormones, and many other substances vital for body homeostasis to and from the cells.

Anatomy of the Heart Location and Size Size = approximately the size of a person’s fist; cone-shaped Weight = less than a pound Location = within the thorax and in between the lungs Apex = pointed part of the heart that rests on the diaphragm and points toward the left hip; where a stethoscope is placed to count the heart rate Base = broader part of the heart; points toward the right shoulder and lies beneath the second rib

Anatomy of the Heart 3 Heart COVERINGS: PERICARDIUM = a double sac of serous membrane that encloses the heart EPICARDIUM = hugs the external surface of the heart and is part of the heart wall. PARIETAL PERICARDIUM = a loosely applied membrane that anchors the heart to the diaphragm and sternum

Anatomy of the Heart 3 LAYERS of the Heart Wall: EPICARDIUM = described earlier MYOCARDIUM = thick bundles of cardiac muscle that actually contracts ENDOCARDIUM = thin sheet that lines the heart chambers

Anatomy of the Heart The heart has 4 chambers = ATRIA & VENTRICLES  The superior atria are RECEIVING CHAMBERS.  Blood flows into the atria from the veins of the body.

Anatomy of the Heart The heart has 2 VENTRICLES TThe inferior ventricles are DISCHARGING CHAMBERS. TThey contract the heart and blood is propelled out of the heart and into circulation.

Although the heart is a single organ, it functions as a double pump: The right side receives oxygen-poor blood from the veins of the body through the large Superior and Inferior Venae Cavae. Blood is then pumped through the Pulmonary Trunk. The pulmonary trunk splits into right and left Pulmonary Arteries, which carry blood to the lungs. Oxygen-rich blood drains from the lungs and is returned to the left side of the heart through the Pulmonary Veins.

Although the heart is a single organ, it functions as a double pump: The circulation from the right side of the heart to the lungs and back to the left side of the heart is called PULMONARY CIRCULATION. Blood returned to the left side of the heart is pumped out of the heart into the Aorta (THE LARGEST ARTERY OF THE BODY). The aorta branches out and supplies all body tissues with oxygen.

Although the heart is a single organ, it functions as a double pump: Oxygen-poor blood circulates from the tissues back to the right atrium and back into the superior and inferior vena cava. The circulation from the left side of the heart through the tissues and back to the right side of the heart is called SYSTEMIC CIRCULATION

Physiology of the Heart Cardiac Cycle In a healthy heart, the atria contract simultaneously. Then, as they start to relax, contraction of the ventricles begin. SSystole - heart CONTRACTION DDiastole – heart RELAXATION

Most of the pumping work is done by the ventricles, so systole and diastole refer to the contraction and relaxation of the ventricles Cardiac Cycle – refers to the events of one complete heartbeat (when both atria and ventricles contract and then relax)  Average heartbeat = 75 times per minute  Length of a normal cardiac cycle = 0.8 second

Physiology of the Heart Heart Sounds: When using a stethoscope, you can hear 2 distinct sounds during each cardiac cycle – HEART SOUNDS The heart sound is “lub” and “dup” (lub- dup)

Blood Vessels Blood circulates inside the blood vessels, which form a closed transport system = Vascular System

Microscopic Anatomy of Blood Vessels Arteries, Veins, and Capillaries AAs the heart beats, blood is propelled into the large arteries leaving the heart. IIt moves into smaller arteries and then into the arterioles. TThe arterioles feed the capillary beds in the tissues. CCapillary beds are drained by venules. VVenules empty into veins that finally empty into the heart. Basically, arteries carry blood AWAY from the heart, and veins carry blood TO the heart.

Physiology of Circulation A good indication of the efficiency of a person’s circulatory system can be obtained by taking their pulse and blood pressure measurements. These measurements along with respiratory rate and body temperature are referred to as VITAL SIGNS.

Arterial Pulse Pulse = a pressure wave that is caused by the expanding and recoiling of an artery that occurs with each beat of the left ventricle The average pulse is beats per minute.

Blood Pressure Blood Pressure – the pressure the blood exerts against the inner walls of the blood vessels Measuring Blood Pressure  Systolic Pressure = the pressure in the arteries at the peak of ventricular contraction  Diastolic Pressure = the pressure when the ventricles are relaxing  Blood pressure is reported with the systolic pressure written first

Effects of Various Factors on Blood Pressure Exercise Emotions Water in the kidneys Temperature Chemicals/Drugs Diet

Developmental Aspects of the Cardiovascular System The heart begins as a tube-like structure that is beating and pumping blood by the 4 th week of embryonic development. Congenital heart defects account for half of all infant deaths. Gradual loss of elasticity in the arteries is an expected consequence of aging.

Developmental Aspects of the Cardiovascular System Cardiovascular disease is an important cause of death in individuals over age 65. Modifications in diet, stopping smoking, and regular aerobic exercise may help to reverse the loss of elasticity in the arteries and prolong life.

Disorders Pericarditis – inflammation of the pericardium Myocardial Infarction – heart attack Fibrillation – a rapid uncoordinated shuddering of the heart muscle. It makes the heart totally useless as a pump and is a major cause of death from heart attacks in adults. Tachycardia – a rapid heart rate (over 100 beats per minute)

Disorders Bradycardia – a slow heart rate (less than 60 beats per minute) Murmurs – abnormal or unusual heart sounds Varicose Veins – common in people who stand for long periods of time and in obese individuals. Blood collects in the feet and legs.

Disorders Hypotension – low blood pressure Hypertension – high blood pressure Coronary Artery Disease – the filling of the blood vessels with fatty, calcified deposits