Chapter Twenty

Home , Coronary sulcus, Fossa ovalis (heart), Interventricular septum, Papillary muscle, Trabeculae carneae

Chapter 22 Outline • Overview of the Cardiovascular System • Anatomy of the Heart • Coronary Circulation • How the Heart Beats: Electrical Properties of Cardiac Tissue • Innervation of the Heart • Tying It All Together: The Cardiac Cycle • Aging and the Heart • Development of the Heart Overview of the Cardiovascular System • The heart propels blood to and from most body tissues via two basic types of blood vessels called ______and ______. • Arteries are defined as blood vessels that carry blood away from the heart. • Veins are defined as blood vessels that carry blood back to the heart. • The arteries and veins entering and leaving the heart are called ______vessels. General Characteristics and Functions of the Heart • Blood flow through the heart is ______because of four valves within the heart. • The heart is functionally two side-by-side pumps that work at the same rate and pump the same volume of blood. – One pump directs blood to the lungs. – One pump directs blood to most body tissues. General Characteristics and Functions of the Heart • The heart generates ______pressure through alternate cycles of the heart wall’s contraction and relaxation. • Blood pressure is the force of the blood pushing against the inside walls of blood vessels. • A minimum blood pressure is essential to circulate blood throughout the body. Pulmonary and Systemic Circulations The cardiovascular system consists of two circulations: 1. ______—right side of the heart and the pulmonary arteries and veins; conveys blood to the lungs and back to the left side of the heart 2. ______—left side of the heart and arteries and veins; conveys blood to most body tissues and back to the right side of the heart Cardiovascular System

Figure 22.1 Position of the Heart • Slightly left of midline deep to the sternum in a compartment of the thorax known as the mediastinum

Figure 22.2 Position of the Heart

• During development, the heart rotates such that the right side or right border (primarily formed by the right atrium and ventricle) is located more anteriorly. • The left side or left border (primarily formed by the left atrium and ventricle) is located more posteriorly. Position of the Heart

• The posterosuperior surface of the heart is mainly the left atrium and is called the base of the heart. • The ______border is formed by the great arterial vessels and the superior vena cava. • The inferior conical end is called the ______. • The ______border is formed by the right ventricle. Position of the Heart

Figure 22.2 Pericardium • The heart is enclosed within a tough sac called the pericardium • Restricts heart movements so that it moves only slightly within the thorax

Figure 22.2 Pericardium

Composed of two parts: 1. ______pericardium—outer covering of tough, dense connective tissue 2. ______pericardium—composed of two layers: • ______layer—lines the inner surface of the fibrous pericardium • ______layer (epicardium)—covers the outer surface of the heart – the small space between the parietal and visceral layers is called the pericardial cavity Pericardium

Figure 22.3 Anatomy of the Heart Wall

The heart wall consists of three distinctive layers (from superficial to deep): 1. ______—consists of the visceral layer of the serous pericardium and areolar connective tissue 2. ______—cardiac muscle; thickest of the three layers 3. ______—internal surface of the heart chambers and external surface of the heart valves Anatomy of the Heart Wall

Figure 22.4 External Heart Anatomy

• Composed of four hollow chambers: two smaller and superior ______(sing., atrium) and two larger inferior ______• The anteroinferior borders of the atria form a muscular extension called the ______• The atria and ventricles are separated from each other by a relatively deep groove called the coronary sulcus • The anterior interventricular sulcus and posterior interventricular sulcus are located between the right and left ventricles and run from the coronary sulcus toward the apex of the heart External Heart Anatomy

Aortic arch Superior vena cava Ligamentum Ascending aorta arteriosum Left pulmonary artery Branches of the Pulmonary trunk right pulmonary artery Left pulmonary veins

Right pulmonary Auricle of left atrium veins Left coronary artery Auricle of right atrium Circumflex artery

Right atrium Great cardiac vein Right coronary artery In anterior (in coronary sulcus) Anterior interventricular interventricular sulcus artery Marginal artery

Right ventricle Left ventricle Small cardiac vein

Inferior vena cava Apex of heart

Descending aorta

Aortic arch

Branches of the Ligamentum arteriosum right pulmonary artery

Ascending aorta Left pulmonary vein

Right pulmonary Pulmonary trunk vein Auricle of left atrium

Left coronary artery

Auricle of right atrium

Right atrium

Right coronary artery Anterior (in coronary sulcus) interventricular In anterior artery interventricular Marginal artery sulcus

Left ventricle Right ventricle

Apex of heart

Figure 22.5 (a) Anterior view

Figure 22.5 External Heart Anatomy

Figure 22.5 Internal Heart Anatomy: Chambers and Valves The heart possesses four chambers: 1. Right atrium 2. Right ventricle 3. Left atrium 4. Left ventricle

The heart also possesses four valves: 1. Right atrioventricular (tricuspid) 2. Pulmonary semilunar 3. Left atrioventricular (bicuspid or mitral) 4. Aortic semilunar Right Atrium

Receives venous blood from heart, the muscles, and systemic circulation; three veins drain into the right atrium: 1. ______vena cava 2. ______vena cava 3. ______sinus

Separating the right atrium from the right ventricle is the right atrioventricular valve (tricuspid valve) Right Atrium

Aortic arch

Ligamentum arteriosum Ascending aorta Left pulmonary artery Superior vena cava Pulmonary trunk

Right pulmonary artery Left pulmonary veins Right pulmonary veins Left atrium Right auricle Aortic semilunar valve Fossa ovalis Interatrial septum Left atrioventricular valve Opening for coronary sinus Pulmonary semilunar Right atrium valve Opening for inferior vena cava Trabeculae carneae Right atrioventricular valve Interventricular septum Chordae tendineae Left ventricle Papillary muscle Right ventricle Septomarginal trabecula Inferior vena cava

Descending aorta

Aortic arch

Ligamentum arteriosum Ascending aorta

Superior vena cava Pulmonary trunk Right auricle

Right atrium

Fossa ovalis Interatrial septum Pectinate muscle Opening for inferior Pulmonary semilunar valve vena cava Right coronary artery Interventricular septum Right atrioventricular valve Left ventricle

Chordae tendineae Trabeculae carneae Papillary muscle Figure 22.6 Right ventricle Coronal section, anterior view

• Deoxygenated venous blood flows from the right atrium to the right ventricle through the right atrioventricular valve. • The right atrioventricular valve is forced closed when the right ventricle begins to contract, preventing blood backflow into the right atrium. Right Ventricle

• Receives deoxygenated venous blood from the right atrium • An ______septum forms a thick wall between the right and left ventricles • The inner wall of each ventricle displays large, irregular muscular ridges called ______Right Ventricle

Aortic arch

Ligamentum arteriosum Ascending aorta Left pulmonary artery Superior vena cava Pulmonary trunk

Descending aorta

Aortic arch

Ligamentum arteriosum Ascending aorta

Superior vena cava Pulmonary trunk Right auricle

Right atrium

Fossa ovalis Interatrial septum Pectinate muscle Opening for inferior Pulmonary semilunar valve vena cava Right coronary artery Interventricular septum Right atrioventricular valve Left ventricle

Chordae tendineae Trabeculae carneae Figure 22.6 Papillary muscle Right ventricle

Coronal section, anterior view

• There are typically three cone-shaped muscle projections inside the right ventricle called ______. • The papillary muscles anchor thin strands of strong connective tissue made up of collagen fibers called ______. • The chordae tendineae attach to three cusps of the (tricuspid) right atrioventricular valve. • Cusps are triangular flaps that hang down into the ventricle. • The chordae tendineae prevent the cusps from prolapsing into the right atrium when the right ventricle contracts. Right Ventricle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Aortic arch

Ligamentum arteriosum Ascending aorta Left pulmonary artery Superior vena cava Pulmonary trunk

Descending aorta

Aortic arch

Ligamentum arteriosum Ascending aorta

Superior vena cava Pulmonary trunk Right auricle

Right atrium

Fossa ovalis Interatrial septum Pectinate muscle Opening for inferior Pulmonary semilunar valve vena cava Right coronary artery Interventricular septum Right atrioventricular valve Left ventricle

Chordae tendineae Trabeculae carneae Figure 22.6 Papillary muscle Right ventricle

Coronal section, anterior view

• At the superior end or roof of the ventricle is a smooth area called the conus arteriosus. • Beyond the conus arteriosus is the pulmonary semilunar valve, which marks the end of the ventricle and the beginning of the pulmonary trunk. Semilunar Valves

• Two of them: pulmonary and aortic • Located in the roof of right and left ventricles, respectively • Each valve is composed of three thin, half- moon-shaped, pocketlike semilunar cusps • When ventricles contract, blood pushes cusps against the arterial trunks • When ventricles relax, some blood flows back toward the ventricles, enters the pockets of the cusps and forces them toward midline, thus closing the valve Valves of the Heart

Figure 22.7 Left Atrium

• Oxygenated blood from the lungs travels through the pulmonary veins to the left atrium. • The left atrium is separated from the left ventricle by the left atrioventricular valve, which is also referred to as the bicuspid or mitral valve. • This valve only has two triangular cusps. • This valve is forced shut when the left ventricle contracts in a similar fashion to the closing of the right atrioventricular valve. Left Ventricle

• The wall is typically three times thicker than the right ventricular wall.

Figure 22.8 Left Ventricle

• The left ventricle has to pump blood to the entire body, except for the lungs, and therefore has to generate a greater blood pressure. • At the superior end or roof of the left ventricle is the aortic semilunar valve, which marks the end of the left ventricle and the beginning of the aorta. Valves of the Heart Valves of the Heart Coronary Circulation

• The ______and ______coronary arteries travel within the coronary sulcus and supply the heart wall muscle with oxygen and nutrients. • The coronary arteries are the only branches given off by the ascending aorta just superior to the aortic semilunar valve. Coronary Arteries

Figure 22.9 Right Coronary Artery

Branches into two arteries: 1. ______artery—supplies the right border of the heart 2. Posterior interventricular artery— supplies the posterior surface of the left and right ventricles Left Coronary Artery

Branches into two arteries: 1. ______artery—also called the left anterior descending artery, supplies the anterior surface of both ventricles and most of the interventricular septum 2. ______artery—supplies the left atrium and ventricle Coronary Veins

Venous return of blood from the heart wall muscle occurs through three major veins: 1. ______cardiac vein—runs alongside the anterior interventricular artery 2. ______cardiac vein—runs alongside the posterior interventricular artery 3. ______cardiac vein—travels close to the marginal artery

All three of the above veins drain into a large vein called the ______sinus that drains into the right atrium. Coronary Veins

Figure 22.9 Conducting System of the Heart

• The myocardium is composed of cardiac muscle fibers. • Cardiac muscle fibers contract as a single unit because they are all connected with low resistance cell-to-cell junctions called gap junctions. • Gap junctions comprise the ______shared by adjacent cardiac muscle fibers. • Therefore, an electrical impulse is distributed immediately and spontaneously throughout the myocardium. Comparison of Cardiac and Skeletal Muscle Structure of Cardiac Muscle

Desmosome

Gap junction

Cardiac muscle cell

Sarcolemma

Nucleus

Mitochondrion (a) Cross section of cardiac muscle cell

Sarcomere Intercalated discs Striations

Sarcolemma Transverse tubule

Sarcoplasmic reticulum

Nucleus

Mitochondrion Myofibrils

LM 1000x

Z disc Z disc H zone (c) Longitudinal section of cardiac muscle

I band M line I band A band (b) Cardiac muscle cell, longitudinal view Figure 22.10 c © Dennis Drenner/Visuals Unlimited Conducting System of the Heart

• The heart exhibits ______, which means it is capable of initiating its own heartbeat independent of external nerves. • The electrical impulse that initiates the heartbeat comes from specialized cardiac muscle cells called the ______(SA) ______or the ______. • The SA node is located on the posterior wall of the right atrium adjacent to the opening of the superior vena cava. • The SA node generates 70–80 impulses per minute under parasympathetic control. Conducting System of the Heart

• Impulses from the SA node travel to the left atrium and the ______(AV) ______located in the floor of the right atrium. • Electrical activity then leaves the AV node into the atrioventricular (AV) bundle (bundle of His), which extends into the interventricular septum. • Once within the septum, the AV bundle divides into ______and ______bundles. Conducting System of the Heart

• These bundles pass the impulse to conduction cells called ______that begin at the apex of the heart. • The Purkinje fibers spread the impulse superiorly from the apex to all of the ventricular myocardium. Conducting System of the Heart

Superior vena cava Right atrium Left atrium Sinoatrial node (pacemaker) Internodal Internodal pathway pathway Atrioventricular node Atrioventricular Atrioventricular bundle Interventricular node (bundle of His) septum Atrioventricular bundle Right bundle Purkinje fibers Purkinje fibers Left bundles

1 Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria and 2 Atrioventricular node cells delay the to the atrioventricular node by the internodal pathway. muscle impulse as it passes to the atrioventricular bundle.

Atrioventricular bundle Interventricular septum

Left and right bundle branches Purkinje fibers 3 The atrioventricular bundle (bundle 4 Within the interventricular septum, the 5 The muscle impulse is delivered to Purkinje of His) conducts the muscle impulse right and left bundles split from the fibers in each ventricle and distributed into the interventricular septum. atrioventricular bundle. throughout the ventricular myocardium.

Figure 22.11 Innervation of the Heart

• The heart, like most other organs, is innervated by both the sympathetic and parasympathetic divisions of the autonomic nervous system. • The anatomical components of both divisions make up the ______. • Autonomic innervation does not initiate a heartbeat, but it can increase or decrease the rate of the heartbeat. Innervation of the Heart

Figure 22.12 Sympathetic Innervation

• Starts with neurons located in T1–T5 segments of the spinal cord • Preganglionic axons enter the sympathetic trunk and synapse on ganglionic neurons. • Postganglionic axons project from all three cervical ganglia and travel to the heart via cardiac nerves. • Sympathetic input to the heart increases the rate and force of heart contractions. Parasympathetic Innervation

• Starts with neurons in the medulla oblongata via the left and right vagus nerves (CN X) • Decreases heart rate but generally has no effect on force of contraction Coordinated Sequence of Heart Chamber Contractions 1. SA node generates an impulse. 2. Both atria contract almost simultaneously (systole) while ventricles are relaxing (diastole). 3. Impulse goes to AV node and then to the ventricles. 4. Ventricles contract (systole) while atria relax (diastole). Ventricular Systole and Diastole

(a) Ventricular Systole (Contraction)

Aortic arch Blood flow into ascending aorta

Ascending Pulmonary aorta trunk Blood flow into Blood flow into right atrium pulmonary trunk

Right Left atrium atrium

Ventricular contraction pushes Ventricles contract, forcing blood against the open AV semilunar valves to open and valves, causing them to close. blood to enter the pulmonary Contracting papillary muscles trunk and the ascending aorta. and the chordae tendineae prevent valve flaps from everting into atria.

Atrioventricular valves closed Semilunar valves open Right ventricle Left ventricle

Cusp of Cusp of atrioventricular semilunar valve valve

Blood in ventricle

Posterior

Left AV valve (closed)

Right AV valve (closed)

Left ventricle Right ventricle Aortic semilunar valve (open)

Pulmonary semilunar valve (open)

Figure 22.13 Anterior Transverse section Ventricular Systole and Diastole

(b) Ventricular Diastole (Relaxation)

Aortic arch

Blood flow into Blood flow into right atrium left ventricle

Right Left atrium atrium

During ventricular relaxation, some blood in the ascending aorta and pulmonary trunk flows back toward the Blood flow into ventricles, filling the semilunar right ventricle valve cusps and forcing them to close. Ventricles relax and fill with blood both passively and then by atrial contraction as AV valves remain open.

Atrioventricular valves open Semilunar valves closed Right ventricle Left ventricle Atrium

Cusp of Blood atrioventricular valve Cusps of Chordae semilunar tendineae valve

Papillary muscle

Posterior

Left AV valve (open)

Right AV valve (open)

Left ventricle Right ventricle

Aortic semilunar valve (closed)

Pulmonary semilunar valve (closed) Figure 22.13 Anterior Transverse section Cardiac Cycle

Atria contract Atria relax Atria relax

Semilunar valves open

AV All AV valves valves valves open closed closed

Ventricles relax Ventricles contract Ventricles contract

1 Atrial systole 2 Early ventricular systole 3 Late ventricular systole Atria contract; AV valves are open, Atria relax; ventricles begin to contract; Atria continue to relax; ventricles contract; semilunar valves are closed AV valves are forced closed (lubb AV valves remain closed; semilunar sound); semilunar valves still closed valves are forced open

Phase Early Late Early Late Atrial ventricular ventricular ventricular ventricular systole systole systole diastole diastole Structure

Atria Contract Relax Relax

V entricles Relax Contract Relax

A V valves Open Closed Open

Semilunar valves Closed Open Closed

Time (seconds) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Atria relax Atria relax

Semilunar valves closed

AV All valves valves open closed

Ventricles relax Ventricles relax

5 Late ventricular diastole 4 Early ventricular diastole Atria and ventricles relax; atria continue Atria and ventricles relax; AV valves passively filling with blood; AV valves remain closed and semilunar valves close open and ventricles begin to passively fill; (dupp sound); atria continue passively Figure 22.14 semilunar valves remain closed filling with blood Blood Flow Through the Heart

Table 22.3 Blood Flow Through the Heart

Superior Right Pulmonary Pulmonary Systemic veins and inferior Right atrioventricular Right semilunar trunk and venae cavae atrium valve ventricle valve arteries

Gas and nutrient exchange Gas exchange in peripheral in the lungs tissues

Aortic Left Systemic Pulmonary Aorta semilunar atrioventricular arteries Left Left veins valve ventricle valve atrium

Chamber of the Heart Receives Blood From Sends Blood To Valves Through Which Blood Flows Right atrium Superior vena cava, inferior vena Right ventricle Right AV valve cava, coronary sinus Right ventricle Right atrium Pulmonary trunk (blood enters Pulmonary semilunar valve vessels of pulmonary circulation) Left atrium Pulmonary veins Left ventricle Left AV valve Left ventricle Left atrium Ascending aorta (blood enters Aortic semilunar valve vessels of systemic circulation) Development of the Heart

Figure 22.15 Development of the Heart

Figure 22.16 Development of the Heart