Chapter 22 Heart

Why have a heart? Move nutrients and oxygen through the body.

How does the heart do its job? First, get oxygen into the blood Second, get oxygenated blood to the rest of the body

Location of heart Slightly left of center, posterior to sternum Fig. 22.2 Location of heart Slightly left of center, posterior to sternum Rotated; right border sits anterior to left border Base of heart is posterior and superior formed by left atrium Superior border formed by ascending aorta, pulmonary trunk, superior vena cava Conical bottom end is apex Inferior border formed by right ventricle Superior border 2nd rib Right border Left border Sternum Diaphragm Inferior border (a) Borders of the heart

Location of heart From anterior view, right ventricle is most obvious Fig. 22.2 Trachea Location of heart Right lung Left lung From anterior view, right ventricle is most obvious Left ventricle sits behind Aortic arch Superior vena cava Pulmonary trunk Ascending aorta Right atrium Left ventricle Right ventricle (b) Heart and lungs, anterior view

Blood flow Fig. 22.6 Blood flows into the heart from the superior vena cava and the inferior vena cava Superior vena cava carries blood from head, neck, arms, superior trunk Inferior vena cava carries blood from lower limbs, inferior trunk This blood is high in CO2 and low in O2 Superior vena cava Pulmonary artery Right atrium Opening for inferior vena cava Right ventricle Inferior vena cava

Blood first enters the right atrium, then the right ventricle Fig. 22.6 Blood first enters the right atrium, then the right ventricle The right ventricle pumps blood out the pulmonary arteries to the lungs In the lungs, the blood exchanges CO2 for O2 Superior vena cava Pulmonary artery Pulmonary artery Pulmonary trunk Right atrium Opening for inferior vena cava Right ventricle Inferior vena cava

Flow and gas exchange in lungs is called pulmonary circulation Fig. 22.1 Systemic circulation 4 Flow and gas exchange in lungs is called pulmonary circulation Lung Lung Basic pattern of blood flow 2 2 Pulmonary circulation 1 Right side of heart Right side Right side 1 3 2 Lungs Pulmonary circulation Oxygenated blood Left side Left side 3 Left side of heart Deoxygenated blood Heart Gas exchange 4 Systemic cells 4 Systemic circulation

Fig. 22.5b Heart, Posterior View Blood returns to the heart through the pulmonary veins The pulmonary veins empty into the left atrium Fig. 22.5b Heart, Posterior View Left pulmonary artery Right pulmonary artery Left pulmonary veins Right pulmonary veins Left atrium Right atrium Left ventricle Right ventricle

The left atrium pumps blood into the left ventricle The left ventricle pumps blood out the aorta to the body Fig. 22.6 Aortic arch Ascending aorta Descending aorta Left atrium Right atrium Left ventricle Right ventricle

Fig. 22.6 Form and Function What differences do you notice between the atria and the ventricles? What’s different between the right and left ventricle? Left atrium Right atrium Left ventricle Right ventricle

Form and Function Atria do not make powerful contractions Fig. 22.6 Atria do not make powerful contractions Left ventricle makes more powerful contractions than right ventricle How does the body ensure blood flows in only one direction? Left atrium Right atrium Left ventricle Right ventricle Copyright © McGraw-Hill Education. Permission required for reproduction or display.

Valves Both atria fill at the same time, contract at the same time Contraction of atria forces open valves between atria and ventricles Right atrioventricular valve (AKA tricuspid valve) separates right atrium from right ventricle Left atrioventricular valve (AKA bicuspid valve) separates left atrium from left ventricle

Valves Fig. 22.7 Right atrioventricular valve (AKA tricuspid valve) separates right atrium from right ventricle Left atrioventricular valve (AKA bicuspid valve) separates left atrium from left ventricle Posterior Left atrioventricular valve Right atrioventricular valve Aortic semilunar valve Fibrous skeleton Pulmonary semilunar valve Anterior

Valves Left atrium Atrioventricular valves are attached to inside of ventricles by chordae tendineae attached to papillary muscles inside ventricle prevents inversion of valve flaps when ventricle contracts typically 3 papillary muscles in right ventricle, 2 in left ventricle Left A/V valve Right A/V valve Chordae tendineae Papillary muscles

Valves Contraction of ventricles forces atrioventricular valves closed and opens semilunar valves

Valves Fig. 22.7 Pulmonary semilunar valve separates right ventricle from pulmonary trunk Aortic semilunar valve separates left ventricle from aorta As ventricles relax, semilunar valves close Posterior Left atrioventricular valve Right atrioventricular valve Aortic semilunar valve Fibrous skeleton Pulmonary semilunar valve Anterior

Valves Semilunar valves don’t have chordae tendineae Left A/V valve Pulmonary semilunar valve Semilunar valves don’t have chordae tendineae Cupped structure of valve fills with blood as ventricles contract, pushing valve back into place Aortic semilunar valve Right A/V valve Chordae tendineae Papillary muscles

Copyright © McGraw-Hill Education Copyright © McGraw-Hill Education. Permission required for reproduction or display. (a) Ventricular Systole (Contraction)

Copyright © McGraw-Hill Education Copyright © McGraw-Hill Education. Permission required for reproduction or display. (b) Ventricular Diastole (Relaxation)

Sounds of a heartbeat Lub-dub, lub-dub, lub-dub “lub” is sound of atrioventricular valves closing “dub” is sound of semilunar valves closing Sounds are not heard best in exact spot of valve Pulmonary semilunar valve Aortic semilunar valve Left atrioventricular valve Right atrioventricular valve Actual location of heart valve Area where valve sound is best heard Locations of individual heart valves and the ideal listening sites for each valve are shown.

Walls of heart chambers Anterior walls of atria lined with muscular ridges called pectinate muscles (pecten = comb) Increase strength of contraction with little increase in heart mass Wall between atria is interatrial septum Pectinate muscles Interatrial septum

Walls of heart chambers Walls of ventricles have larger, more irregular muscular ridges called trabeculae carneae Assist with contraction, pull on papillary muscles, prevent formation of vacuum during contraction Wall between ventricles is interventricular septum Trabeculae carneae Interventricular septum

Heart wall structure Epicardium is visceral layer of pericardium Fig. 22.3 Heart wall structure Visceral layer of serous pericardium (epicardium) Epicardium is visceral layer of pericardium Myocardium: cardiac muscle thickest layer contracts to pump blood Endocardium: innermost layer simple squamous epithelium (AKA endothelium) and areolar connective tissue Heart wall Myocardium Endocardium

Myocardium (cardiac muscle) Fig. 22.4 Simple squamous epithelium Epicardium (visceral layer of serous pericardium) Areolar connective tissue and fat Myocardium (cardiac muscle) Areolar connective tissue Endocardium Endothelium

Fibrous skeleton of heart Fig. 22.7 Dense regular connective tissue Structural support between atria and ventricles Anchor for heart valves Rigid framework for attachment of cardiac muscle tissue Electric insulator between ventricles Posterior Left atrioventricular valve Right A/V valve Aortic semilunar valve Fibrous skeleton Pulmonary semilunar valve Anterior

Pericardium Heart sits inside pericardium fibrous sac – very tough Fig. 22.2 Pericardium Mediastinum Left lung Heart sits inside pericardium fibrous sac – very tough serous lining made of two layers of epithelial tissue with tiny amount of water between Ascending aorta Pleura (cut) Pericardium (cut) Apex of heart Diaphragm (cut) (c) Serous membranes of the heart and lungs

Pericardium Restricts heart movement, prevents bouncing Fig. 22.2 Pericardium Posterior Restricts heart movement, prevents bouncing Prevents heart overfilling with blood Thoracic vertebra Right lung Left lung Aortic arch (cut) Heart Sternum Anterior (d) Cross-sectional view

Pericardium Outer layer is fibrous pericardium Fibrous pericardium Fig. 22.3 Pericardium Fibrous pericardium Outer layer is fibrous pericardium dense connective tissue attached to diaphragm and base of aorta, pulmonary trunk, vena cava Parietal layer of serous pericardium Pericardial cavity Visceral layer of serous pericardium (epicardium) Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity

Pericardium Inner layer is serous pericardium Fibrous pericardium Fig. 22.3 Pericardium Inner layer is serous pericardium double layer formed from single “balloon” stretched around heart parietal layer connected to fibrous pericardium pericardial cavity contains serous fluid secreted by serous membranes visceral layer covers outside of heart (AKA epicardium) Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity Visceral layer of serous pericardium (epicardium) Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity

Pericarditis Inflammation of pericardium makes blood vessels leaky Fig. 22.3 Pericarditis Inflammation of pericardium makes blood vessels leaky Fluid accumulates in pericardial cavity prevents heart from pumping fully

External anatomy of heart Fig. 22.5a External anatomy of heart Coronary sulcus extends around heart between atria and ventricles Blood vessels in adipose tissue run through sulci Right and left coronary arteries supply blood to heart wall only branches off ascending aorta Ascending aorta Left coronary artery (in coronary sulcus) Right atrium Circumflex artery (in coronary sulcus) Right coronary artery (in coronary sulcus) Right ventricle Left ventricle Apex of heart Descending aorta

External anatomy of heart Fig. 22.5a External anatomy of heart Ascending aorta Circumflex artery supplies left atrium and ventricle Left coronary artery (in coronary sulcus) Right atrium Circumflex artery (in coronary sulcus) Right coronary artery (in coronary sulcus) Right ventricle Left ventricle Apex of heart Descending aorta

Fig. 22.9 (a) Coronary arteries Aortic arch Pulmonary trunk Superior vena cava Left coronary artery Aortic semilunar valve Left atrium Right atrium Circumflex artery Branches of left coronary artery Right coronary artery Anterior interventricular artery Posterior interventricular artery Branches of right coronary artery Right marginal artery Left ventricle Right ventricle Right coronary artery branches into right marginal artery: supplies right border of heart posterior interventricular artery: supplies posterior left and right ventricles

Fig. 22.9 (a) Coronary arteries Aortic arch Pulmonary trunk Superior vena cava Left coronary artery Aortic semilunar valve Left atrium Right atrium Circumflex artery Branches of left coronary artery Right coronary artery Anterior interventricular artery Posterior interventricular artery Branches of right coronary artery Right marginal artery Left ventricle Right ventricle Left coronary artery branches into circumflex artery: supplies left atrium and left ventricle anterior interventricular artery: supplies anterior left and right ventricles and interventricular septum pattern of arterial branching varies among individuals

Blood returns from cardiac muscle through cardiac veins Fig. 22.9 (b) Coronary veins Polymer cast of coronary vessels Aortic arch Superior vena cava Pulmonary trunk Left atrium Right atrium Coronary sinus Middle cardiac vein Small cardiac vein Great cardiac vein Right ventricle Left ventricle Blood returns from cardiac muscle through cardiac veins Great cardiac vein runs beside anterior interventricular artery Middle cardiac vein runs by posterior interventricular artery Small cardiac vein runs by right marginal artery All drain into coronary sinus on posterior heart drains into right atrium

Page 664 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Enlarged heart Abnormal growth of heart can cause swelling in limbs, dizziness, irregular heartbeat, shortness of breath, sudden death Cardiomegaly in an adult female. Note how the heart shadow encompasses most of the width of the thorax. Normal heart on x-ray © ISM/Phototake

Fig. 22.7 Contraction of bundles: Narrows heart Shortens heart Cardiac muscle bundles Spiral arrangement of cardiac muscle Cardiac muscle Fibers arranged in spiral bundles around and between heart chambers Contractions start at top of atria, move around atria, then start from bottom of ventricle and travel up

transverse (T) tubules Fig. 22.10 Openings of transverse (T) tubules Intercalated disc Cardiac muscle Folded sarcolemma fibers are striated intercalated discs have desmosomes and gap junctions link cells electrically and mechanically impulses sent immediately form one cell to next Desmosomes Intercalated discs Gap junctions Endomysium Sarcolemma Cross section of cardiac muscle cells Nucleus (b) Intercellular junctions Mitochondrion

Fig. 22.11 1. Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria and to the atrioventricular node by the internodal pathway. Sinoatrial node (pacemaker) Internodal pathway Atrioventricular node Atrioventricular bundle (bundle of His) Purkinje fibers Left bundles Purkinje fibers Heart is autorhythmic starts its own beating Specialized cells that initiate and conduct muscle impulses are collectively the conducting system Right bundle

2. Atrioventricular node cells delay the Fig. 22.11 Sinoatrial node (pacemaker) Internodal pathway Atrioventricular node Atrioventricular node Atrioventricular bundle 2. Atrioventricular node cells delay the muscle impulse as it passes to the atrioventricular bundle.

Fig. 22.11 Sinoatrial node (pacemaker) Internodal pathway Atrioventricular node Atrioventricular node Atrioventricular bundle 3. The atrioventricular bundle (bundle of His) conducts the muscle impulse into the interventricular septum. Atrioventricular bundle Interventricular septum

Fig. 22.11 4. Within the interventricular septum, the left and right bundles split from the atrioventricular bundle. Atrioventricular bundle Interventricular septum Left and right bundles

Fig. 22.11 5. The muscle impulse is delivered to Purkinje fibers in each ventricle and distributed throughout the ventricular myocardium. Atrioventricular bundle Interventricular septum Left and right bundles Purkinje fibers

Fig. 22.11 Superior vena cava Right atrium Left atrium Sinoatrial node (pacemaker) Internodal pathway Internodal pathway Atrioventricular node Atrioventricular node Atrioventricular bundle (bundle of His) Interventricular septum Atrioventricular bundle Right bundle Purkinje fibers Left bundles Purkinje fibers 1 Muscle impulse is generated at the sinoatrial node. It spreads throughout the atria and to the atrioventricular node by the internodal pathway. 2 Atrioventricular node cells delay the muscle impulse as it passes to the atrioventricular bundle. Atrioventricular bundle Interventricular septum Left and right bundles Purkinje fibers 3 The atrioventricular bundle (bundle of His) conducts the muscle impulse into the interventricular septum. 4 Within the interventricular septum, the left and right bundles split from the atrioventricular bundle. 5 The muscle impulse is delivered to Purkinje fibers in each ventricle and distributed throughout the ventricular myocardium.

Page 669 1 3 2 0.8 second R +1 Millivolts P wave T wave Q S Copyright © McGraw-Hill Education. Permission required for reproduction or display. 0.8 second R +1 1 P wave 3 T wave Millivolts Q S 2 QRS complex –1 The events of a single cardiac cycle as recorded on an electrocardiogram.

Ventricular systole Contraction of ventricles Semilunar valves open Fig. 22.13a Copyright © McGraw-Hill Education. Permission required for reproduction or display. (a) Ventricular Systole (Contraction) Ventricular systole Aortic arch Blood flow into ascending aorta Ascending aorta Pulmonary trunk Contraction of ventricles Semilunar valves open Blood flows into arteries Larger of blood pressure measurements Blood flow into right atrium Blood flow into pulmonary trunk Right atrium Left atrium Ventricular contraction pushes blood against the open AV valves, causing them to close. Contracting papillary muscles and the chordae tendineae prevent valve flaps from everting into atria. Ventricles contract, forcing semilunar valves to open and blood to enter the pulmonary trunk and the ascending aorta. Atrioventricular valves closed Semilunar valves open Right ventricle Left ventricle Cusp of atrioventricular valve Cusp of semilunar 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) Anterior Transverse section

Ventricular diastole Relaxation of ventricles AV valves open Copyright © McGraw-Hill Education. Permission required for reproduction or display. Fig. 22.13b (b) Ventricular Diastole (Relaxation) Ventricular diastole Aortic arch Blood flow into right atrium Blood flow into left ventricle Relaxation of ventricles AV valves open Blood flows into ventricles from atria Smaller of blood pressure measurements Right atrium Left atrium During ventricular relaxation, some blood in the ascending aorta and pulmonary trunk flows back toward the ventricles, filling the semilunar valve cusps and forcing them to close. Blood flow into right ventricle 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 atrioventricular valve Blood Cusps of semilunar valve Chordae tendineae Papillary muscle Posterior Left AV valve (open) Right AV valve (open) Left ventricle Right ventricle Aortic semilunar valve (closed) Pulmonary semilunar valve (closed) Anterior Transverse section

Fetal circulation Inferior vena cava flows into right atrium Fig. 23.27 Fetal circulation Inferior vena cava flows into right atrium Much of the blood bypasses lungs through foramen ovale, opening between right and left atria Ductus arteriosus takes blood directly from pulmonary trunk to aorta Some blood flows through pulmonary system and left side of heart, continues normal pathway Umbilical arteries carry blood to placenta

Fetal Cardiovascular Structure Postnatal Structure Ductus arteriosus Fig. 23.27 Superior vena cava Aortic arch Ductus arteriosus Pulmonary artery Pulmonary trunk Pulmonary veins Foramen ovale Lung Right atrium Right ventricle Heart Liver Ductus venosus Inferior vena cava Descending abdominal aorta Umbilical vein Umbilicus (not visible) Common iliac artery Urinary bladder Umbilical arteries Internal iliac artery Umbilical cord Placenta 8 7 1 2 3 4 5 6 Fetal Cardiovascular Structure Postnatal Structure Ductus arteriosus Ligamentum arteriosum Ductus venosus Ligamentum venosum Foramen ovale Fossa ovalis Umbilical arteries Medial umbilical ligaments Umbilical vein Round ligament of liver (ligamentum teres)

Other heart structures Fig. 22.6 Other heart structures Ligamentum arteriosum Fossa ovalis is location of former fetal foramen ovale hole that moved blood between atria, bypassing lungs Ligamentum arteriosum connects pulmonary trunk to aorta fibrous structure that forms from fetal ductus arteriosus Coronary sinus drains blood from coronary veins Fossa ovalis Opening for coronary sinus