The Cardiovascular System 11 The Cardiovascular System

The Cardiovascular System Cardio = realting to the ________? Vascular = relating to the ____________? CV System includes the heart, blood vessels, and about 5 liters of blood (5 liters ~ 1.3 gallons) At a resting rate the heart is able to pumps 5 liters of blood throughout the entire body every minute.

Functions of the Cardiovascular System Transportation – of oxygen, nutrients, hormones, and cellular waste Protection – blood contains white blood cells and platelets Regulation – maintain body temperature by controlling blood flow to the skin

The Heart Location Orientation About the size of your fist Thorax between the lungs in the inferior mediastinum Orientation Pointed apex directed toward left hip Base points toward right shoulder About the size of your fist Weighs less than a pound Thorax – between neck and abdomen

Midsternal line 2nd rib Sternum Diaphragm (a) (base of heart) Sternum Diaphragm Point of maximal intensity (PMI) (a) Figure 11.1a

Mediastinum Heart Left lung Posterior MEDIASINUM - the central compartment of the thoracic cavity surrounded by loose connective tissue, contains a group of structures within the thorax. The mediastinum contains the heart and its vessels, the esophagus, trachea, phrenic and cardiac nerves, the thoracic duct, thymus and lymph nodes of the central chest. Figure 11.1b

Aorta Left lung Diaphragm (c) Superior vena cava Aorta Parietal pleura (cut) Pulmonary trunk Left lung Pericardium (cut) Apex of heart Diaphragm (c) Figure 11.1c

Brachiocephalic trunk Left common carotid artery Superior vena cava Left subclavian artery Right pulmonary artery Aortic arch Ligamentum arteriosum Ascending aorta Left pulmonary artery Pulmonary trunk Left pulmonary veins Right pulmonary veins Left atrium Auricle of left atrium Right atrium Circumflex artery Right coronary artery in coronary sulcus (right atrioventricular groove) Left coronary artery in coronary sulcus (left atrioventricular groove) Anterior cardiac vein Left ventricle Right ventricle Great cardiac vein Marginal artery Anterior interventricular artery (in anterior interventricular sulcus) Small cardiac vein Inferior vena cava Apex (a) Figure 11.3a

The Heart: Coverings Pericardium—a double-walled sac that encloses the heart Fibrous pericardium connects heart to the diaphragm and sternum Serous membrane is deep to the fibrous pericardium and composed of two layers Visceral pericardium Next to heart; also known as the epicardium Parietal pericardium Outside layer that lines the inner surface of the fibrous pericardium Serous fluid fills the space between the layers of pericardium

The Heart: Heart Wall Three layers Epicardium Myocardium Endocardium Outside layer This layer is the visceral pericardium Connective tissue layer Myocardium Middle layer Mostly cardiac muscle Endocardium Inner layer

Right pulmonary artery Left atrium Superior vena cava Aorta Left pulmonary artery Right pulmonary artery Left atrium Right atrium Left pulmonary veins Right pulmonary veins Pulmonary semilunar valve Left atrioventricular valve (bicuspid valve) Fossa ovalis Aortic semilunar valve Right atrioventricular valve (tricuspid valve) Left ventricle Right ventricle Chordae tendineae Interventricular septum Inferior vena cava Myocardium Visceral pericardium (b) Frontal section showing interior chambers and valves. Figure 11.3b

The Heart: Chambers Right and left side act as separate pumps Four chambers Two Atria Blood receiving chambers Right atrium Left atrium Two Ventricles Blood discharging chambers Right ventricle Left ventricle

Left ventricle Right ventricle Muscular interventricular septum Figure 11.5

The Heart’s Role in Blood Circulation Pulmonary circulation (Right side of heart) Carries deoxygenated (oxygen-lacking) blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart. Systemic circulation (Left side of heart) Carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart.

Arteries vs. Veins Arteries  carry blood away from the heart Veins  carry blood to the heart

Pulmonary Circulation Superior Vena Cava (vein) – takes deoxygenated blood from the head, neck, and arms to right atrium Inferior Vena Cava (vein) – takes deoxygenated blood from the lower body to right atrium Right ventricle receives blood from the atrium Pulmonary artery – carries deoxygenated blood from the right ventricle to the lungs

Systemic Circulation Pulmonary Vein – carries oxygenated blood from lungs to the left atrium From the left atrium the blood is pumped into the left ventricle Aorta (artery) – carries oxygenated blood from the left ventricle to the entire body

The Heart: Valves Allow blood to flow in only one direction to prevent backflow Four valves Atrioventricular (AV) valves—between atria and ventricles Tricuspid valve (right side of heart) Bicuspid (mitral) valve (left side of heart) Open during heart relaxation and closed during ventricular contraction Semilunar valves—between ventricle and artery Pulmonary semilunar valve Aortic semilunar valve Closed during heart relaxation but open during ventricular contraction

Notice these valves operate opposite of one another to force a one-way path of blood through the heart

Valve Support Papillary Muscles Chordae Tendineae located in the ventricles of the heart attach to the cusps of the atrioventricular valves via the chordae tendineae prevent inversion or prolapse of these valves Chordae Tendineae cord-like tendons that connect the papillary muscles to the AV valves in the heart

AV valves close. Ventricles (a) Operation of the AV valves Blood returning to the atria puts pressure against AV valves; the AV valves are forced open. 1 Ventricles contract, forcing blood against AV valve flaps. 4 5 AV valves close. As the ventricles fill, AV valve flaps hang limply into ventricles. 2 Chordae tendineae tighten, preventing valve flaps from everting into atria. 6 Atria contract, forcing additional blood into ventricles. 3 Ventricles AV valves open; atrial pressure greater than ventricular pressure AV valves closed; atrial pressure less than ventricular pressure Figure 11.6a, step 6

(b) Operation of the semilunar valves Pulmonary trunk Aorta As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open. 1 As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the leaflets of semilunar valves and forcing them to close. 2 Semilunar valves open Semilunar valves closed Figure 11.6b, step 2

Blood Flow Through the Heart Superior and inferior venae cavae dump deoxygenated blood from the body into the right atrium From right atrium, through the tricuspid valve, blood travels to the right ventricle From the right ventricle, blood leaves the heart via the pulmonary semilunar valve into the pulmonary artery The pulmonary artery carries blood to the lungs

Blood Flow Through the Heart In the lungs oxygen is picked up and carbon dioxide is dropped off Oxygen-rich blood returns to the heart through the four pulmonary veins The pulmonary veins dump blood into the left atrium The blood is pumped through the bicuspid valve into the left ventricle From the left ventricle, blood leaves the heart via the aortic semilunar valve to the aorta and then the aorta carries blood throughout the body

The Heart: Cardiac Cycle The cardiac cycle refers to a complete heartbeat From its generation to the beginning of the next beat So includes the diastole and systole of all four chambers Systole = contraction Diastole = relaxation The frequency of the cardiac cycle is described by the heart rate (beats per minute - BPM) Atria relax, when ventricles contract Ventricles relax, when atria contract

The Heart: Heart Sounds The first heart tone, "Lub“, is caused by the closure of the mitral and tricuspid valves Ventricles are contracted (systole) Atria are relaxed (diastole) The second heart tone, "Dub“, is caused by the closure of the aortic valve and pulmonic valve  Ventricles diastole Atria systole